Exchange student– Civil EngineeringHorsens, 25.09.2012 Daria Maria Biskupska (18 ECTS) PROJECT NR 11 “Foundation for Skyscraper in urban area. Use diaphragm walls and top & down method” Supervisors: Sara Kjærgaard 4/5 Søren Fisker 1/5
[email protected] [email protected] Tele: + 45 87 55 42 82 Tele: +45 87 55 41 04 Table of Contents 1 1. General introduction .................................................................................................. 5 1.1. The aim of the project........................................................................................................................ 5 1.2. Localization ....................................................................................................................................... 5 1.3. Construction and general characteristic of the building .................................................................... 6 1.4. Climate .............................................................................................................................................. 7 1.5. Project assumptions/Delimitation ...................................................................................................... 8 2. Geological Analyze .................................................................................................... 9 2.1.General information about soils in Poland .......................................................................................... 9 2.2. Local soils on the site ........................................................................................................................ 9 2.3. Previous drilling in the area ............................................................................................................. 10 2.3.1. Information according to Polish geo - engineering database........................................................ 10 Information according to Geobad ................................................................................................. 13 3.Retaining structures – analyze................................................................................. 15 Introduction ........................................................................................................................................ 15 3.1. Types of earth support systems ...................................................................................................... 16 3.1.1. Diaphragm walls........................................................................................................................... 16 3.1.2. Pile walls ...................................................................................................................................... 19 3.1.3. Soldier pile with wooden lagging walls ......................................................................................... 20 3.1.4. Sheet pile walls ............................................................................................................................ 22 3.2. Comparison ..................................................................................................................................... 23 3.2.1. Best solution................................................................................................................................. 23 4. Types of diaphragm wall – analysis and selection the best type ......................... 24 4.1. Cantilever diaphragm wall embedded in soil ................................................................................... 24 4.2. Strutted diaphragm wall .................................................................................................................. 25 4.3. Anchored diaphragm wall ................................................................................................................ 26 4.4. Conclusion ...................................................................................................................................... 27 5.Deep excavation methods – analyze ....................................................................... 28 5.1. General introduction about deep excavations ................................................................................. 28 5.2. Types of deep excavations methods ............................................................................................... 28 5.2.1. Bottom-up method........................................................................................................................ 29 5.2.2. Top and down method .................................................................................................................. 29 5.3. Conclusion ...................................................................................................................................... 34 6. Skyscraper in Wroclaw: underground garage – stages of construction ............. 35 7.Geotechnical description ......................................................................................... 39 2 7.1. Introduction to soil properties .......................................................................................................... 39 7.2. Soil physical properties ................................................................................................................... 41 7.3. Soil characteristics .......................................................................................................................... 42 7.3.1. Determination of weight density ................................................................................................... 42 7.3.2. Determination of characteristic undrained shear strenght ............................................................ 43 7.3.3. Determination of characteristic angle of shearing resistance ....................................................... 43 7.3.4. Determination of parameters for soils occurring in the project ..................................................... 43 8. Introduction to calculations .................................................................................... 45 8.1. Introduction – Designing foundations by calculation according to Eurocode 7 ................................ 45 8.1.1. Partial factor safety ...................................................................................................................... 45 8.1.2. Geotechnical design by calculation .............................................................................................. 45 8.1.3. Designed values of actions .......................................................................................................... 46 8.1.4. Designed values of geotechnical parameters............................................................................... 46 8.1.5. Designed values of geometrical data ........................................................................................... 46 8.1.6. Designed effects of actions .......................................................................................................... 47 8.1.7. EQU ............................................................................................................................................. 47 8.1.8. GEO ............................................................................................................................................. 48 8.1.9. STR .............................................................................................................................................. 48 8.1.10. GEO/STR Limit States ............................................................................................................... 49 8.2. Retaining wall design ...................................................................................................................... 49 8.2.1. Limit states ................................................................................................................................... 49 8.2.2. Future unplanned excavation ....................................................................................................... 50 9. Diaphragm wall calculations ................................................................................... 51 9.1. General assumptions for project ..................................................................................................... 51 9.2. Descriptions of calculations ............................................................................................................. 52 9.3. Geo5 calculations............................................................................................................................ 75 10. Duration and prices ............................................................................................... 78 11. Safety and organization ......................................................................................... 79 11.1. Safety and organization the building site ....................................................................................... 79 11.2. Temporary dewatering ................................................................................................................... 80 12. Conclusion ............................................................................................................. 81 13. References .............................................................................................................. 82 ANNEXES ANNEX 1. Project description ANNEX 2. Pictures 3 ANNEX 3. Soil profiles ( cut sections: I, II, III, IV) ANNEX 4. Soil classification system according to Eurocode 7 ANNEX 5. PN81-03020 ANNEX 6. PN EN 1997-1 Soil characteristics ANNEX 7. PN EN 1997-1 Factors for safety, Ultimate limit-State, coefficient ANNEX 8. PN EN 1997-1 Loss of static equilibrium (Examples) ANNEX 9. PN81-03010 ANNEX 10. GEO5 graphs for PHASE 5 DRAWINGS DRAWING NR 1. LAND USE PLAN 1:500 DRAWING NR 2. LAYOUT DRAWING OF UNDERGROUND PARKING 1:100 DRAWING NR 3. CALCULATED CROSS SECTION WITH LOCATION 1:100 DRAWING NR 4. CONSTRUCTION DRAWING OF DIAPHRAGM WALL 1:50 1. General introduction 4 After few analysis. by doing the most of the calculations by GEO5. 1. Figure 1. it was possible to find all internal forces in diaphragm walls (in each step of garage building process) and compare the results in a short period time.1. to design the construction for chosen structures. Excavation as a process is a major challenge because of the extent of the work-area and volumes. Localization This project is about excavation works for Skyscraper in Wroclaw. In order to have more clear understanding of the overall problem. More pictures from building site are enclosed as ANNEX 1. More-over. the best solutions have been found: diaphragm walls and top & down method. which will make the construction more complex in many ways. to find proper retaining structures. Figure 1. Important issue in terms of this particular case is drainage and it is analyzed and possible solutions are presented.1.2 Location of Skyscraper in Wroclaw. The aim of the project The aim of this project was to analyze geotechnical information about the area. 5 . Wroclaw is the third-largest city in Poland. it is very important to have an organizational plan for the excavation works . It is briefly analyzed and planned in this current project. In order to provide continuous work flow in urban area. there are some more studies in the following chapters of the project. including the excavation works. Equally important task was calculation and dimensioning of diaphragm walls by using software and also doing calculations by hand.2.1 Location of Wroclaw The Skyscraper will be situated in the center of the down.the organization plan was prepared and it is included in this project. to find the best deep excavation method and organization plan for excavation-works. Construction and general characteristic of the building The building is designed as in-situ reinforced concrete frame. The building is a conventional structures (typical multistory construction).0 meters. The area of the building is 1200m2 and the usable space is 5097m2. The real name of the building is “Office building of tax chamber”.3 Skyscraper 1.4. This Skyscraper is designed by company „AA Studio” architects.1. The Skyscraper is established as Geotechnical Category 2. Figure 1.3. with 2 under-ground stories and 11 aboveground stories. The roof of the building is planned to be around at the level of +40. Climate 6 . Precipitation is different throughout the year.Study of the climate is very important when carrying out the works. The graph below shows the Temperature relations in the city of Wroclaw during the year. snow) This is the mean monthly precipitation. snow.4 Average minimum and maximum temperature over the year. Figure 1. but snow cover seldom lasts long. If the works takes place in a rainy period the problems with the water will be higher. hail etc.4 cm with the maximum in July. The monthly mean minimum and maximum daily temperature. Snow during January and February is common and the average temperatures for these two winter months are near the freezing point. Snowfall occurs mainly from late November until early March. its essential that for designed excavation it’s necessary to pick the months with the temperatures above the freezing point Figure 1. including rain. because it changes the conditions of the works. 7 . also if it is a snowy period it will be more difficult to work with the concrete/bentonite. Wroclaw experience precipitation from 2 cm to 8.5 Average monthly precipitation over the year (rainfall. Generally. html [2] http://www.investmap. calculations of structure and drawings.weather. The used materials and design solutions should ensure proper water tightness. The deformations of the retaining structure should be limited. Also it will be designed the deep excavation method with steps of formations the structure. as well as limitation for major deformations and stresses within the structure. After the project finalization all interior surfaces have to appear dry and without signs of water intrusion.pl/dolnoslaskie-infrastruktura-spoleczna-f77/nowa-siedziba-izby-skarbowejt6129. The construction process and management of the groundwater should be treated with special attention. following the environmental protection act. The life expectancy for the retaining structure is 100 years. Designing process contains: analysis of different possibilities. References: [1] http://forum. 1. The basement slab has to be designed to act as a foundation.6 Average monthly hours of sunshine over the year.Figure 1. The best time is from May till August.5 Project assumptions/Delimitation This project is about a Parking under Skyscraper in Wroclaw. and it requires the design of the retaining structure of the parking basement. The safety of the construction should be guaranteed.com/weather/today/Wroclaw+Poland+PLXX0029 8 . so the environment is not compromised. with the first 25 years without important maintenance works. This is the monthly total of sunhour To improve working conditions excavation work should be carried out in good light. but it won´t be calculated in this project. hence not causing damage to the surrounding buildings. and content of silt particles less than 0. Sources of knowledge: • Internet : Polish geo-engineering database 9 . it is quintessential to have sufficient knowledge about the soil and characteristics of it. Geological Analyze 2.2. The main type of soils include swampy boulder loam. organogenic soils developed on peat.2mm in diameter) occupy about 50 % of the total area. Sandy formations (20% of particles less than 0. substratum soil profile layers. As this current project is about deep excavations. Table 1 Parent rock – soil types in Poland 2. Geological analysis according to existing information in some circumstances can point out some aspects that should be focused on during geotechnical drillings. there are two bases of information about soils in the location of designed Skyscraper’s garage. More data on soil types in Poland are shown in Table 1. Soil classification system according to Eurocode 7 [ PN EN 19971:2004] is enclosed as ANNEX 4. Soils in Poland Poland has many different soils.02 mm in diameter. By geological analysis the wider background of current area is briefly introduced. Their water properties depend upon the depth of the ground-water table. alluvial soils. silty and loess formations.1 General information about soils in Poland In Poland Eurocode 7 is obligatory. Appropriate agrotechnical and land reclamation (water conservation) measures are necessary for the improvements of these soils.2 Local soils on the site In this project. point 2.) 2. It is not enough to design the foundation. but it was made for other project and the building in that project was in different location (the distance from that building to the Skyscraper in is less than 1 km) Unfortunately.comment: datebase has a lot of information about the area of Wroclaw. Figure 2.1 Information according to Polish geo-engineering database The geo-engineering database and the geo-engineering atlas of the Wrocław agglomeration were prepared between 2007 and 2008 by Geological Enterprise of Wrocław PROXIMA and the Polish Geological Institute in the collaboration with Geological Enterprise of Katowice and the Geological Company Geoprojekt Szczecin. it was impossible to get detailed information about soils in designed area from design engineer who is engaged in designing Skyscraper in Wroclaw. It is necessary to assume soils according to available data ( details .3 Previous drilling in the area 2.3. but not very accurate.1. That kind of documentation is prepared by specialist and expensive.3. • Geological documentation made by Polish Company GEOBAD comment: documentation is very detailed. 10 .1 Wroclaw – division of the city according to Polish Internet database. Figure 2.8 km2.3 Wroclaw –location of building site scale 1:1000(red place). Żórawina. Święta Katarzyna. The average density of survey points were 70 boreholes per km2 of the agglomeration area. Borehole profiles collected in the database have been used to prepare 6 geo-engineering sections in the scale of 1:5000 / 1:200 to present the geological structure synthetically. The geo-engineering database and the geo-engineering atlas of the Wrocław shows soils at three levels: • at a depth of 1 meter • at a depth of 2 meters • at a depth of 4 meters Maps (print screens) from the database with descriptions are given below: 11 .The Atlas of Wrocław covers the area of Wrocław City County (293 km2) as well as parts of the neighbouring communes of Wrocław County (Długołęka. Figure 2. Kobierzyce and Kąty Wrocławskie Communes) and Środa Śląska County (Miękina Commune). The total area covered by the maps is 719. The database of the geo-engineering atlas of the Wroclaw contains more than 50 000 boreholes that come from archives and were also made especially for the purpose of this project.2 Wroclaw –location of building site Scale 1:10000(red place). Czernica. soils at 2 meters according to Polish Internet database Figure 2.5) and a depth of 4 meters (Figure 2.6 Building site .6) in Wroclaw city center is : glacial till Figure 2.4 Building site .5 Building site .soils at 4 meters according to Polish Internet database 12 .at a depth of 1 meter in Wroclaw city center is : fill (embankment) Figure 2.soils at 1 meter according to Polish Internet database. at a depth of 2 meters (Figure 2. 2 – 6.0 – 5.4 semi dry 3 2.1 Information according to GEOBAD According to the GEOBAD – Polish Company. following information are assumed (adopted at my own discretion for this project): • There are 4 boreholes assumed for this project: - Borehole nr 1 - Borehole nr 2 - Borehole nr 3 - Borehole nr 4 Data for boreholes: Borehole nr 1 Nr Deep [m p.1 – 2.1 Embankment - Loose wet 2 1. which made research in Wroclaw for one project in 2011.2 Clayey silt saclSi IL=0.07 semi dry 4 5.3.2. Based on given data. GEOBAD is a geo-engineering company.0 Fine sand FSa ID=0.] Layer Symbol Density Humidity 1 0 – 1. That project was about multistory building located less than 1 km from designed Skyscraper.5 wet 13 .p. there have been some previous drilling in the area near designed skyscraper.t.4 silty sand siSa ID=0. t.8 meters.8 Clayey silt saclSi IL=0.8 – 3.33 semi dry 3 1.8 – ∞ clayey silt saclSi IL=0.0 Clayey silt saclSi IL=0.39 semi dry 3 2.4 – 2.7 silty sand siSa ID=0.] Layer Symbol Density Humidity 1 0 – 0.9 Embankment - Loose wet 2 0.8 – 4.p.4 Embankment - Loose wet 2 1. This is a result of geological history.09 dry 4 4. it can be estimated what kind of soil is present at this place by using two closest holes and guessing what is between them. According to information above.22 wet Borehole nr 3 Nr Deep [m p.12 semi dry 4 5.27 wet Borehole nr 4 Nr Deep [m p.2 – 5.0 – 6.1 – ∞ clayey silt saclSi IL=0.3 Embankment - Loose wet 2 1.9 – 1.] Layer Symbol Density Humidity 1 0 – 1.1 silty sand siSa ID=0.4 – ∞ clayey silt saclSi IL=0.t.8 Fine sand FSa ID=0. 14 .5 wet 5 4.Cut section III (between borehole nr 3 and borehole nr 4) .29 wet Borehole nr 2 Nr Deep [m p. Ground waters are very deeply located under the ground level and surface waters appear very seldom.5 6.2 – 4.3 – 2. four cut sections are assumed: . Due to the present conditions.Cut section II (between borehole nr 2 and borehole nr 3) .07 semi dry 4 3.7 – ∞ clayey silt saclSi IL=0. ground water level for this project is assumed at depth of 11.8 wet 5 6.2 Fine sand FSa ID=0.29 wet Using information about boreholes .2 Fine sand FSa ID=0. it is possible to prepare soil profiles.Cut section IV (between borehole nr 4 and borehole nr 1) Cut sections are enclosed as ANNEX 3 Area of Wroclaw is very poor of water resources. in problematic places where no drillings are made.p.p.4 semi dry 3 2.8 Clayey silt saclSi IL=0.t.Cut section I (between borehole nr 1 and borehole nr 2) .] Layer Symbol Density Humidity 1 0 – 1. gas. Structures in the immediate vicinity of excavations. Vibration from blasting. water. parking and for housing of building utilities. however. and the space around the excavation. dense traffic scenario. As the number of deep excavations in city is seen to increase exponentially so are the problems associated with their construction. During excavation. Support provision for excavation depends on the type of soil in the area. and material loads near the cut can also cause earth to collapse in sandy soil. or natural gases and oxygen deficient atmosphere • Dewatering problems • Wet.3. soft clay can prove to be very treacherous. soil heterogeneity (including fill and remains of old foundations or other unexpected obstructions). Unsupported excavations pose several hazards. slushy ground conditions.1. inadequate space for equipment. Introduction Urban settings pose unique challenge to the construction Industry. 15 . and the following list gives some of the important ones: • Very high risk potential of collapse or failure of excavation walls and consequently posing hazard to workers and equipment • Hazards during excavation due to presence of public utilities. Heavy traffic and lack of adequate space has compelled Civil engineers to excavate deeper into the ground to create additional floor space to meet increasing space requirements for amenities. Clayey soils in general. Clearly. The instability can be caused by moisture changes in the surrounding air or changes in the water table. Sandy soil is always considered dangerous even when it is allowed to stand for a period of time after a vertical cut. some soil types pose greater problems than others. trips. complicated by limited spaces in which personnel work • Ground and/or ground water table changes affecting nearby structures. foundation interaction (the detrimental effects of construction of new structures on the surrounding buildings). the depth of the excavation.In the end there will be the answer for question: Why diaphragm walls are the best solution according to site conditions? 4. traffic and heavy machinery movement. causing slips. the type of foundation being built. Special features of urban areas are restricted movements. Silty soils are also unreliable and require the same precautions and support provision as sand. such as electricity. effects of changes in the water table. present less risk than sand. presence of underground obstructions and utilities have made excavations a formidable task to execute. or falls. deep excavations are posing mounting problems that demand a site specific and tailor made retaining solution. Retaining structures .analyze In chapter different types of retaining walls will be described and compared . high capacity vertical foundation elements. Diaphragm walls provide structural support and water tightness.1. 16 . • ground conditions.1m. Following types of deep support systems are commonly used in metropolitan cities. permanent basement walls for facilitating Top-down construction method. internal strutting etc. Diaphragm walls Diaphragm walling is a technique of constructing a continuous underground wall from the ground level. Short widths of 2. The wall is constructed panel by panel in full depth.1. tunnels. • working space limitations etc. 4. • subsequent • construction methodology. These reinforced concrete diaphragm walls are also called Slurry trench walls due to the reference given to the construction technique where excavation is made possible by filling and keeping the wall cavity full with bentonitewater mixture during excavation to prevent collapse of vertical excavated surfaces. 2.1. 3. Panel width varies from 2. Tangent or Secant) Soldier pile with wooden lagging walls Sheet pile walls Composite supporting systems – that is. water control.5m are selected in less stable soils. These retaining structures find following applications: • • • • • • • earth retention walls for deep excavations. 5. • availability of construction know-how. basements. • ground water level. 1. • cost factors. One of the key governing factors is the requirement of water tightness of the retaining structure. 3. The criteria for the selection of these systems are: • excavation depth. • allowable vertical and horizontal displacements of adjacent ground.6 to 1. Typical wall thickness varies between 0. Diaphragm walls Pile walls (Contiguous.3. retaining wall foundations. any of the retaining systems (1) to (4) above strengthened by Anchors. Types of earth support system Several in-situ support systems have been deployed for containing deep excavations.5m to about 6m. other equipment involved are cranes. 17 . pumps. There is a minimum of space wasted.1 It must be remembered that Diaphragm walls are constructed as a series of alternating primary and secondary panels. In limited headroom conditions. 3. Once the diaphragm walls are constructed. Steps involved in the construction of diaphragm wall can be broadly listed as follows: 1. Before the intermediate secondary panel excavation is taken up. Diaphragm walls however. Diaphragm wall construction is relatively quiet. The water tight walls formed can be used as permanent structural walls and are most economical when used in this manner. Lowering reinforcement cage 5. The finished structural wall formed prior to excavation allows subsequent construction of the basement in a water tight and clean environment. site area. Alternate primary panels are constructed first which are restrained on either side by stop-end pipes. where the conventional grabs are undeployable. Guide wall construction along alignment 2. require the use of heavy construction equipment that requires reasonable headroom. L are possible to form and used for special purposes. Water stoppers are sometimes used in the construction joints between adjacent panels to prevent seepage of ground water. air lifts. Work may be carried out right against existing structures and the line of wall may be adjusted to any shape in plan. Concreting using tremie The sequence of construction of diaphragm wall panel has been schematically illustrated in Fig. Bentonite flushing 4. tanks. Slurry wall technique is a specialized technique and apart from the crane mounted Grab. They are not considered efficient means in hard and rocky grounds. desanding equipment. Trenching by crane operated Grab/ hydraulic grab 3. work can be planned to proceed simultaneously above and below the ground level. Different panel shapes other than the conventional straight section like T. the pipes are removed and the panel is cast against two primary panels on either side to maintain continuity. mixers etc. and minimum noise and vibration levels make it suitable for construction in urban areas.under very high surcharge or for very deep walls. smaller cranes can be used though this could compromise efficiency. and considerable mobilization costs. 1 The sequence of construction of diaphragm wall panel 18 .Figure 3. Pile walls (Contiguous.6. or on encountering competent stratum at a depth which is different than that anticipated during design. Figure 3. These piles are connected with a Capping beams at the top. Contiguous piles facilitate deployment of several independent sets of equipment and gangs along its alignment which can speed up its execution. They are considered more economical than diaphragm wall in small to medium scale excavations due to reduction in cost of site operations. and thus protects the neighboring structures. which assists equitable pressure distributions in piles.3. These retaining piles are suitable in areas where water table is deep or where soil permeability is low. some acceptable amount of water can be collected at the base and pumped out. Provision of Contiguous piles restricts ground movements on the backfill side. Tangent piles are used when secant piling or diaphragm walling equipment is not available.1.2. Diameter and spacing of the piles is decided based on soil type. Tangent or Secant) Contiguous Pile walls will be described as an example. In Contiguous bored pile construction. where traditional retaining methods would otherwise encroach the adjoining properties. Secant bored piles are formed by keeping this spacing of piles less than the diameter.0m.2 Schematic Arrangement of Contiguous Piled Retaining System Contiguous piles serving as retaining walls are popular since traditional piling equipment can be resorted for their construction. center to center spacing of piles is kept slightly greater than the pile diameter. 19 . unlike the diaphragm wall – which relies on the orthogonal geometry of the excavated area – contiguous pile retaining system can constructed to form any shape in the excavated area.2). ground water level and magnitude of design pressures.3. foundations and boundary walls from the detrimental effects of the excavation. Such retaining systems has advantage of employing varying diameter of piles in lieu of change in sub-surface conditions. Contiguous piles are suitable in crowded urban areas. However. Further. They can be constructed using even the conventional piling equipment. Large spacing is avoided as it can result in caving of soil through gaps. There are different types of pile walls (Fig. and can be constructed in hard and rocky sub-soil conditions where diaphragm wall construction is difficult. 0. Common pile diameters adopted are 0.8 and 1. horizontal Waling beams and supporting elements (struts. Ground anchors are increasingly used in such supports due to easy access to equipment.1. These walls have successfully been used since the late 18th century in metropolitan cities world over. anchors or nails) are erected. Mumbai 3. Excavation proceeds step by step after placement of Soldier piles at the periphery of the excavation. At some predetermined levels. In design parlance. Excavating in small stages and installing wooden lagging. Constructing soldier piles at regular intervals (1 to 3m on center typically) 2. only the portion of concrete and steel away from the neutral axis is known to offer resisting moment. As a result. Passive soil resistance is obtained by embedding the soldier piles beneath the excavation grade.3 Contiguous piles supporting excavation at Worli. Moment resistance in soldier pile and lagging walls is provided solely by the soldier piles. This type of retaining system involves the following broad based activities: 1. 20 . 3. wooden laggings are placed spanning from one soldier pile to another.3. some concrete and steel area remains under-utilized. Depending on the ground conditions. not considered suitable for construction in areas of high water table. and this in turn is found to affect the dimension and alignment of the Capping beams. Backfilling and compacting the void space behind the lagging. Soldier piles are driven/ bored at regular interval and allowed to gain strength. The lagging bridges and retains soil across piles and transfers the lateral load to the soldier pile system.They are however. Figure 3. Soldier pile with wooden lagging walls Soldier pile and lagging walls are some of the oldest forms of retaining systems used in deep excavations. Perfect alignment of piles is often difficult to achieve at site. as retention and containing water is not possible in contiguous piles. The major disadvantages of soldier pile and lagging systems are that they are primarily limited to temporary construction. New Delhi 21 . Because only the flange of a soldier pile is embedded beneath subgrade. They are commonly preferred in narrow excavations for pipe laying or similar works.5 Soldier Piles and Wooden Lagging System at Udyog Bhawan.4 Soldier Pile and Wooden Lagging System Soldier pile and lagging walls are the most inexpensive systems compared to other retaining walls. They are not as rigid as other retaining systems. Poor backfilling and associated ground losses can result in significant surface settlements.Figure 3. Figure 3. it is very difficult to control basal soil movements. They are also very easy and fast to construct. These are found to be suitable for soils with some cohesion and without water table. They cannot be used in high water table conditions without extensive dewatering. but are also used for deep and large excavations in conjunction with struts. 5x10-10 m/s with hydro swelling joints Traditional sheet pile shapes are “Z” type and “U” type. Sheet pile walls A pile is designed to be beaten into the ground next to other piles already set up.Greater than 10-7 m/s with joints without sealant . Figure 3. Use of sheet pile walls to retain contaminated soil requires very low leakage rates and therefore must necessarily use special fixing at the locks. Each sheet pile are set between themselves via lateral veins called locks. Z sections are considered one of the most efficient pile available today. silent and resulting in no vibration on adjacent structures. Once planted into the ground. The material can be wood. wax or water blowing. Z-Type (Z): Used for intermediate to deep wall construction. Generally the following permeability is expected: .10-7 m/s with tar or wax seals . but mostly steel. it is more interesting to drive the piles with a hydraulic cylinder: this method.Type. The locks are the weaknesses of the sheet pile walls.piles are commonly used for cantilevered and tiedback systems.7 Z-Type sheet piles 22 .3. requires soil differential settlement in long term state.4.1. Besides welding. There are several shapes of sheet pile. Z. these devices are based on the use of bituminous materials. Additional applications also include load bearing bridge abutments. In an urban context. their assembly may form a retaining wall or a waterproof screen. “U” Type (U) sheet piles are used for the applications similar to Z. The nature of steel sheet tends to concentrate the leak rates in the locks. These differences come from the performance of their joints.6 U-Type sheet piles Figure 3. 3. tangent. Comparison The following table is suitable to summarize the above. and that makes them less expensive. secant) + + 3.1. The best solution taking all features into consideration are diaphragm walls and that is why they will be used in this case (from north. Benefits of Diaphragm Walls: • • • • • • • • • Installed to considerable depths Walls with substantial thickness can be formed Flexible in plan layout Easily incorporated into permanent works Wall (sections) can be designed to carry vertical load Basement construction time reduced Economical solution for large. south and west and east site). Best solution The problem is that we are in an urban area. Soldier pile with wooden lagging walls Diaphragm medium medium medium medium small medium hight medium NOISE/ VIBRATION medium high small medium WATER TIGHTNESS + - TRANSFORMING INTO BASEMENT WALLS - - + + medium medium medium medium Sheet pile walls COST WEIGHT TIME OF IMPLEMENTATION walls Pile walls (contiguous. so vibration has to be avoided.2. deep basements in saturated and unstable soil profiles Noise levels limited to engine noise Vibration-less 23 . with close buildings surrounding.2. Parameters of sheet pile walls and diaphragm walls are almost the same but diaphragm walls are more common in Poland. Cantilever diaphragm wall embedded in soil Cantilever walls are walls that do not have any supports and thus have a free unsupported excavation. Cantilever walls restrain retained earth by the passive resistance provided by the soil below the excavation. Figure 3.8 Cantilever diaphragm wall with maximum dimensions. struts. These cases are: • Cantilever diaphragm wall embedded in soil • Strutted diaphragm wall • Anchored diaphragm wall Third example concerns an excavation within strutted diaphragm wall – method of support of excavations walls very common in Poland. This sections examines vertical cantilever walls and the basic design methods used for cantilever wall analysis.4.1. Types of diaphragm wall.analysis and selection the best type In chapter different types of diaphragm walls will be described. Many engineers use the cantilever wall term to actually describe gravity walls. etc. 4. 24 . In reality both gravity and vertical embedded walls types can be categorized as cantilever if no lateral bracing support is provided by means of tiebacks. In the end there will be the answer for question: Which type of diaphragm wall is the best solution according to underground building construction ? Calculations of three standard designed problems are performed in this point. 11 Example of single strutted diaphragm wall and stress distribution. Figure 3.the maximum length of wall above the ground (Hn) is 4 meter or less.Figure 3. 25 .8.2. In this project there are 2 floors of underground garage. Cantilever diaphgram wall is impossible in this case because as we can see in the Figure 3. Strutted diaphragm wall Figure 3.10 Single and double strutted diaphragm wall with maximum dimensions. 4.9 Example of cantilever diaphragm wall with stress distribution. so the dimension Hn will be more than 4 meters. that means that it is ideal dimension for 2 floors of underground garage.3. In this project retaining wall could be strutted by floor slabs. e. 4. Anchored diaphragm wall Anchored diaphragm walls are often used when securing deep foundation pits.g.Strutted diaphgram wall is recommended for this project.14 Anchored diaphragm wall 26 . in built-up areas or under groundwater levels Figure 3.13 Anchored diaphragm wall with dimensions Figure 3. The maximum dimension of the wall above the ground (Hn) is 12 meters. and slabs can take over the role of struts. The maximum dimension of the wall above the ground (Hn) is 12 meters. 27 . The construction of garage will be used in two ways – slabs can take to loads from cars and other object in garage. Cantilever diaphragm wall was excluded. To act as 'strut' and be the support for diaphragm wall. 4.Anchored diaphgram wall is also recommended for this project.15 Under-ground construction Basement reinforced concrete slabs roles: 1. that means that it is ideal dimension for 2 floors of underground garage. Due to the construction of floors in garage (reinforced concrete slabs). To transform the load from cars and other objects. to the columns. it seems to be the better idea to use strutted method. 2.4. Conclusion In sum we have to choose between strutted and anchored method. The connection between diaphragm wall and each slab is designed as fixed (rotation of the slab towards diaphragm wall is impossible) The best method is strutted diaphragm wall. and next to the ground. Figure 3. this damage may include a combination of building settlement because of a loss of lateral support. underpinning. noise.and post-construction condition surveys • Emergency response in the event of a failure • Analysis of the cause of failure • Evaluation of differing site conditions claims • Evaluation of the suitability of temporary shoring and dewatering systems • Analysis of building or ground deformation resulting from a loss of lateral support • Vibration analysis • Evaluation of construction activities and response to construction difficulties • Review proposed excavation plans 5. traffic congestion). shoring. preconstruction surveys of adjacent properties and utilities. loss of use. construction accidents. and/or alterations to operations.5. Adjacent construction may be a nuisance to neighboring property owners (e. specification of responses to construction difficulties. General introduction about deep excavations The construction of deep excavations in the urban environment is a technically challenging problem. adjacent property owners claim constructioninduced damage. Types of deep excavations methods It is already known that diaphragm walls are the best solution for this project. felt vibrations. or delays in completion. and local building codes. Frequently.analyze In chapter different types of deep excavations methods (concern diaphragm walls) will be described and compared. and structural damage.1. cosmetic finish distress. Correct analyze of deep excavation includes: • Pre.In the end there will be the answer for question: Why top & down method is the best solution in this case? 5. differing site conditions.. Walls can be made extremely stiff and therefore better resistant to deflection. and structure construction. Temporary cut-offs can also be created using this technique. field observations during construction.2. construction errors. right of entry agreements. Deep excavations methods. excavation installation. striking unknown utilities. business interruption. state. design of excavation support systems. For deep excavations. unforeseen natural events. dust. Design and construction typically involves many steps including site characterization. Although excavations are regulated by federal. There are two main methods of building construction with underground garage: 1. .g. bottom-up method 28 . problems occur in the process of developing a site due to many factors including design errors. It is also possible to use effective internal propping with a diaphragm wall rather than the normal ground anchors. PROCEDURE The typical construction procedure of top down construction is as follows 1. Keep constructing the superstructure till it gets finished. Cast the floor slab of first basement level 5. Begin to construct the superstructure 6. 4. 5. Place the steel columns or stanchions where the piles are constructed.1. The top/down method has been used for deep excavation projects where tieback installation was not feasible and soil movements had to be minimized.2.2. Proceed to the second stage of excavation. Top and down method Top-down construction method as the name implies. Proceed to the first stage of excavation. Though this conventional method.2. buildings with underground basements are built by bottom-up method where sub-structure and super-structure floors are constructed sequentially from the bottom of the substructure or lowest level of basement to the top of the super-structure. underpasses and subway stations. it is not feasible for the gigantic projects with limited construction time and/or with site constraints. tall buildings with deep basements and underground structures such as car parks. The basement columns (typically steel beams) are constructed before any excavation takes place and rest on the load bearing elements. In this case the basement floors are constructed as the excavation progresses. Construct the retaining wall. also called as bottom-up method. Bottom-up method Conventionally. The sequence construction begins with retaining wall installation and then load-bearing elements that will carry the future super-structure. cast the floor slab of the second basement level. Top-down construction method which provides the significant saving of the overall construction time has been adopted for some major projects where time factor is of primary importance. Complete the basement 9. is a construction method. etc. Repeat the same procedure till the desired depth is reached 8. top and down method 5. 29 . Top-down method is mainly used for two types of urban structures. These load bearing elements are typically concrete barrettes constructed under slurry (or caissons). Construct the foundation slab and ground beams.2. Construct piles. 3. 2. is simple in both design and construction. which builds the permanent structure members of the basement along with the excavation from the top to the bottom. 7. Step nr 2: Excavation and installation of steel strut Figure 4.2 Installation of retaining wall The underground retaining wall which is usually a diaphragm wall.3 Excavation and installation of steel strut 30 .1 Top and down construction method Step nr 1: Installation of retaining wall Figure 4.Figure 4. is installed before excavation commences. and this process progresses downwards till the base slab is completed Step nr 5: Construction of underground structure Figure 4. The roof slabs not only provides a massive support across the Step nr 4: Construction of underground structure Figure 4. with access openings provided on the slab for works to proceed downwards.4 Construction of underground structure part II The next level of slab is constructed. which in turn support the soil at the sides Step nr 3: Construction of underground structure Figure 4.The soil is excavated just below roof slab level of the underground structure.5 Construction of underground structure part III 31 . Struts are installed to support the retaining walls.4 Construction of underground structure part I The roof slab is constructed. The side walls are constructed upwards. The access openings on the roof slab are then sealed STRUCTURAL MEMBERS REQUIRED FOR TOP-DOWN CONSTRUCTION Design and construction principles for top-down method primarily call for two major structural elements.2m in thickness with sufficient embedment in firm soil layers is commonly used as a retaining wall whereas prefabricated steel columns known as Stanchions embedded in either large diameter deep-seated bored piles or barrettes are utilized as structural columns. Figure 4. Excavation for basement must be carried out with the support of permanent retaining wall so that basement floor slabs can be utilized as lateral bracing. Figure 4.6 illustrates the top-down construction method with utilization of stanchions and diaphragm wall. followed by removal of the intermediate struts. Columns with sufficient capacity must be pre-founded in bored piles or barrettes to sustain the construction load and to utilize as part of bracing system.8m to 1.6 Top-down construction with stanchion and diaphragm wall TYPES OF STANCHION AND THEIR APPLICATION TYPES OF STANCHION General information Light stanchion Material & Example Size Steel H-beams 350x350x137kg/m Medium sized stanchion Steel H-beams 350x350x390 kg/m Application For semi top-down construction • For temporary decking For semi and full top-down construction of shallow to 32 . Diaphragm wall of 0. stanchion is installed immediately after completion of bored pile concreting process. stanchion is installed immediately after completion of drilling and reinforcement lowering prior to concreting process.8. General construction steps involved in this method are demonstrated in Figure 4. Though installation details may be different from one contractor to another. post-concreting or plunging installation and pre-concreting installation or placing stanchion prior to concreting.7. Guide frame is used to install the stanchion at the correct position. General construction sequence involved in this method is demonstrated in Figure 4. In some projects stanchion is attached to the last section of reinforcement and installed together with the reinforcement. Figure 4. size of stanchion and size of bored or barrette piles.Heavy stanchion Steel H-beams 508x457x738kg/m • Composite steel columns built up by 2 or more small to medium size H-beams • Large section pre-cast RC column (seldom use) STANCHION INSTALLATION METHODS medium deep excavation Full top-down construction in deep excavation Stanchion installation method is usually selected by the piling contractor who takes into consideration three main factors such as installation depth. stanchion installation can be categorized under two main methods.7 general construction sequence of pre-concreting installation method Pre concreting method In this method. 33 . Post-concreting installation or plunging method In this method. It requires highly skilled supervision and labour force. the lateral displacement of retaining wall or ground settlement may possible increase due to the influence of creep if the soil layers are encountered.3.8 general construction sequence of pre-concreting installation method Advantages and disadvantages Advantages: 1. 3. Top down construction is the need of the hour as it is highly time efficient and is becoming popular and is coming more and more in practice with every passing day. It is also very efficient way of doing two way construction to save time. 3. It is highly suitable for construction for tall buildings with deep basements to be constructed in urban areas. 2. 4. Skyscrapers with deep basements in urban areas should be constructed using top down method. car parks etc. It is suitable for structures with deep basements like underground rails. 34 . The higher stiffness of floor slab compare to steel struts improves the safety of excavation.Figure 4. But top down construction needs very efficient planning and designing and skilled supervision and labour force. Disadvantages: 1. The shortened construction period due to simultaneous construction of the basement and the superstructure. 2. Since the construction period of the basement is lengthened. Higher cost (due to the construction of pile foundation) 2. More operational space gained from the advanced construction of floor slabs. CONCLUSION From the above chapter we can conclude that top down construction has its suitability for certain kind of mega structures. The construction quality may influence because of worsened ventilation and illumination under floor slab. 5. weight 80100 cm . Retaining wall installation: First step of retaining wall installation: Guidewall construction .6. Skyscraper in Wroclaw: underground garage – stages of construction According to previous chapter. OPERATIONS PRIOR TO EXCAVATION The sequence construction begins with retaining wall installation and then load-bearing elements that will carry the future super-structure. dimensions: height :120 cm. long – depending on the building Second step of retaining wall installation: Panel (vertical segments) excavation 35 . following steps of construction were prepared by GEO5 software. Third step of retaining wall installation: Installation of the reinforcement The last step of retaining wall installation: Bentonite filling During diaphragm wall installation. Basement columns and the concrete barrettes are load-bearing elements that will carry the future super-structure. the basement columns (steel beams) and concrete barrettes are made. 36 . The construction process of those elements is beyond the scope of this project. Step nr 1 -Ground floor construction Figure 4.10 Example of whole in a top floor slab 37 .EXCAVATION: STEP NR 1 The top floor slab is constructed with at least on construction (glory) hole left open to allow removal of spoil material (Figure 4.9 Excavation .9) Top-down construction involves casting the ground floor slab and excavating the ground below while work on the superstructure above can continue Figure 4. EXCAVATION: STEP NR 2 The excavation starting at the glory hole begins once the top floor has gained sufficient strength. Soil under the top basement floor is excavated around the basement columns to slightly lower than the first basement floor elevation in order to allow for the installation of the forms for the first level basement slab.Step nr 2 .11 Excavation . Each floor rests on the basement columns that were constructed earlier Figure 4. Glory holes are left open within each newly formed basement floor slab and the procedure is repeated.Second level basement slab (foundation slab) construction 38 .Step nr 3 .12 Excavation .First level basement slab construction EXCAVATION: STEP NR 3 Figure 4. Shear strength is a term used to describe the magnitude of the shear stress that a soil can sustain. The stress-strain relationship levels off when the material stops expanding or contracting. in the heart of Wroclaw.located next to the area which will be excavated and possibly causing the collapse to these road and buildings as a result of the excavation or dewatering. Introduction to soil properties Geotechnical description is the last step of 'theoretical part' before the calculation. particulate material may expand or contract in volume as it is subject to shear strains.8 meters under the ground level. the dewatering should then be arranged so that the water table is lowered at least 1 meter below the excavation level. It is necessary to determine the physical and mechanical properties of materials. 11 meters.1. Geotechnical description 7. and when interparticle bonds are broken. The shear resistance of soil is a result of friction and interlocking of particles. In case when the excavation is at depth e. the structure founded on it can collapse. In this part the subsurface conditions and materials are investigated. Figure 4. Due to interlocking. 39 . If soil expands its volume. It is really important to have an overview on the surrounding buildings because the Skyscraper will be located in an urban area. There will probably be a dug in clay. Water level is between at depth 11. If the soil fails. in which case the dewatering of the excavation possibly will be done by simple drainage.13 Foundation failure by liquefaction after the 1964 Niigata Earthquake. the peak strength would be followed by a reduction of shear stress.g. the density of particles will decrease and the strength will decrease. The safety of any geotechnical structure is dependent on the strength of the soil. and road . in this case. Understanding shear strength is the basis to analyze soil stability problems. So it is not necessary to perform a temporary dewatering for the excavation (the deep of excavation is 7 meters).7. The geotechnical description is important in all kind of project in civil engineering. The building site is surrounded by other buildings. and possibly cementation or bonding at particle contacts. 20 Low 20 .Table 5 the shear strength of soils when measured by Field or Hand Shear Vane Apparatus.75 High 75 .According to BS EN ISO 14688-2:2004.150 Very high 150 . or in the laboratory by Quick Undrained Triaxial compression test.600 Shear Strength in Soils: • The shear strength of a soil is its resistance to shearing stresses • It is a measure of the soil resistance to deformation by continuous displacement of its individual soil particles • Shear strength in soils depends primarily on interactions between particles • Shear failure occurs when the stresses between the particles are such that they slide or roll past each other • Soil derives its shear strength from two sources: Cohesion between particles (stress independent component) 1.5. is a measure of the forces that cement particles of soils Figure 4. in kPa u Extremely low <10 Very low 10 . Cementation between sand grains 2.40 Medium 40 .14 Cohesion on soils Internal friction angle (φ) is the measure of the shear strength of soils due to friction 40 .3. shall be expressed as below: Table 4 shear strength of soils Term based on measurement Undrained Shear Strength classification definition C . Electrostatic attraction between clay particles Frictional resistance between particles (stress dependent component) Cohesion • Cohesion (C).300 Extremely high 300 . 15 Internal friction angle 7.63 mm to 2. mull. In the United States. but the most common constituent of sand in inland continental settings and non-tropical coastalsettings is silica (silicon dioxide. for example aragonite. its components are changed into forms usable by plants. medium sand (¼ mm – ½ mm). consists of about 60 percent carbon. medium and coarse with ranges 0. some clay minerals are formed by hydrothermalactivity. Clay deposits may be formed in place as residual deposits in soil. These solvents. by low concentrations of carbonic acid and other diluted solvents. sand or asphalt) Humus It's the layer of organic matter in soil. by various forms of life. like coral and shellfish. Clay minerals are typically formed over long periods of time by the gradual chemical weathering of rocks. and smaller amounts of phosphorus and sulfur. The composition of sand is highly variable.Figure 4. which has mostly been created. sand is commonly divided into five sub-categories based on size: very fine sand (⅟16 – ⅛ mm diameter).2. Sandy clay Soil material that contains 35 % or more clay and 45% or more sand. Gravel 41 . As humus decomposes. and the vegetation from which it is derived. depending on the local rock sources and conditions. usually acidic. fine sand (⅛ mm – ¼ mm). Clay deposits are typically associated with very low energy depositional environmentssuch as large lakes and marine basins. but thick deposits usually are formed as the result of a secondary sedimentary deposition process after they have been eroded and transported from their original location of formation. coarse sand (½ mm – 1 mm). Clay Clay is a general term including many combinations of one or more clay minerals with traces of metal oxides and organic matter.063 mm to 0. 6 percent nitrogen. Fill From the building demolition or base course (mix concrete. the types of organisms involved in its decomposition. ISO 14688 (International Organization for Standardization) grades sands as fine. usually in the form of quartz. over the past half billion years. migrate through the weathering rock after leaching through upper weathered layers. which ranges in colour from brown to black. The second most common form of sand is calcium carbonate. In addition to the weathering process.0 mm. Soil physical properties There are different types of soil in the designed area.2 mm to 0. Humus. Humus is classified into mor. or moder formations according to the degree of its incorporation into the mineral soil. Sand Sand is a naturally occurring granular material lcomposed of finely divided rock and mineral particles. and very coarse sand (1 mm – 2 mm). or SiO2). Geologic clay deposits are mostly composed of phyllosilical minerals containing variable amounts of water trapped in the mineral structure. usually silicatebearing. 75 1.65 siSa wet Example: 42 .33 – 0.67 – 0.65 1.7 1. Globally.85 FSa semi dry 2.k • fk weight density [kN/m3] characteristic undrained shear strength of soil [kPa] characteristic angle of shearing resistance [0] 7.to boulder-sized fragments. 7.1.16 in) andpebble gravel (>4 to 64 mm or 0. especially in rural areas where there is little traffic. Soil characteristics According to Eurocode 7 and Polish National Standards PN-81 B-03020 (Annex 5) the following geotechnical parameters have to be known to calculate the underground structure (in this case underground parking): • g • cu. Both sand and small gravel are also important for the manufacture of concrete. Determination of weight density (g) Density represents weight (mass) per unit volume of a substance.000 mi) of gravel roads.Is composed of unconsolidated rock fragments that have a general particle size range and include size classes from granule.0 – 0.24 ID = 0. Gravel is sub-categorized by the Udden-Wentworth scale into granular gravel (>2 to 4 mm or 0.85 1.5 in). far more roads are surfaced with gravel than with concrete or tarmac.0 1.0 1.9 1. Russia alone has over 400. Soil density is expressed in two well accepted concepts as particle density and bulk density.6 1.3.3.68 ID = 0. with a number of applications. One cubic yard of gravel typically weighs about 3000 pounds (or a cubic metre is about 1. Many roadways are surfaced with gravel.2 to 2. Gravel is an important commercial product.7 2. Bulk Density: The oven dry weight of a unit volume of soil inclusive of pore spaces is called bulk density.000 km (250.079 to 0.800 kilograms). The bulk density of a soil is always smaller than its particle density. According to PN-81 B-03020 (ANNEX 5) : Table for cohesionless soils: SOIL HUMIDITY Particle density gS dry Bulk density g depending on the ID ID = 1. Particle Density: The weight per unit volume of the solid portion of soil is called particle density. Determination of characteristic angle of shearing resistance [0] Angle of shearing resistance is also called internal angle of friction or angle of frictional resistance.7 cu. The shear strength of a fine-grained soil under undrained condition is called the undrained shear strength.k] Drained condition occurs when there is no change in pore water pressure due to external loading.9 7. 7. angle between the axis of normal stress and the tangent to the Mohr envelope at a point representing a given failure-stress condition for the solid material. picture nr 5 the characteristic undrained shear resistance can be assumed from the graph.0 0 22 2 Fine sand FSa ID=0.5 0 30 3 Clayey silt saclSi IL=0.4 characteristic angle of shearing resistance can be assumed from the graphs. the pore water can drain out of the soil easily. In a drained condition.25 IL = 0.3. picture nr 3.4 semi dry 16. the rate of loading is much quicker than the rate at which the pore water is able to drain out of the soil. As a result.For Fine Sand (dry.k [kPa] 43 . Determination of parameters for soils occurring in the project.25 – 0. resulting in an increase in the pore water pressure.07 semi dry 21 35 20.The tendency of soil to change volume is suppressed during undrained loading.3.4. Determination of characteristic undrained shear strength [cu.65 g*cm3 Table for cohesion soils: Bulk density g depending on the IL Particle density gS SOIL saclSi 2. causing volumetric strains in the soil.3.00 1.10 2.5) the particle density equals 2.3. Definition: Angle representing the relationship of shearing resistance to normal stress acting on the sliding surface within a soil mass during shear.68 IL < 0 ID = 0. Based on Annex 5. Based on Annex 5.65 g*cm3 and the bulk density equals 1.0 – 0. Undrained condition occurs when the pore water is unable to drain out of the soil. most of the external loading is taken by the pore water. In an undrained condition.5 – 1. Borehole nr 1 g[kN/m3] 0 fk [ ] Nr Layer Symbol Density Humidity 1 Embankment - Loose wet 18. ID = 0.0 2. 7.5 IL = 0.15 2.2. k [kPa] fk [ ] Borehole nr 4 g[kN/m3] 0 fk [ ] Nr Layer Symbol Density Humidity 1 Embankment - Loose wet 18.27 wet 20 27 16.5 5 Clayey silt saclSi IL=0.33 semi dry 16.5 0 30.0 0 22 2 Fine sand FSa ID=0.39 semi dry 16.5 0 30 3 Clayey silt saclSi IL=0.4 Silty sand siSa ID=0.3 16.5 cu.6 Borehole nr 2 0 Nr Layer Symbol Density Humidity g[kN/m3] cu.5 fk [ ] Borehole nr 3 0 Nr Layer Symbol Density Humidity g[kN/m3] 1 Embankment - Loose wet 18.12 semi dry 21 36 20 4 Silty sand siSa ID=0.0 0 28 3 Clayey silt saclSi IL=0.22 wet 21 30 17.5 4 Clayey silt saclSi IL=0.k [kPa] 44 .3 16.8 wet 18.0 0 22 2 Fine sand FSa ID=0.5 5 clayey silt saclSi IL=0.5 wet 17.07 semi dry 21 35 22 4 silty sand siSa ID=0.5 wet 17.29 wet 20 28.4 semi dry 16.09 dry 21 36 22.6 cu.5 0 30.5 5 Clayey silt saclSi IL=0.5 0 30.29 wet 20 28.k [kPa] 1 Embankment - Loose wet 18.5 0 30 3 Clayey silt saclSi IL=0.0 0 22 2 Fine sand FSa ID=0. 1.1.1. Introduction to calculations In chapter following rules will be described and explained: partial factors of safety. Geotechnical design by calculation The algorithm below shows the steps of calculations The algorithm was prepared by Dr Ian Smith from Edinburgh Napier University 8. 8.8. Introduction – Designing foundations by calculation according Eurocode 7 8. Designed values of actions 45 .1 Partial factor of safety There are different partials of safety according to EN 1997-1: Polish Standard PN 81 B – 03020 (ANNEX 5) use “g” for unit weight (weight density) In calculations designed values are used by combining the characteristic value with the appropriate factor of safety.1.2. 8.3. method of geotechnical design by calculation. method of retaining wall design by calculation. To determine design effects of action we follow the steps: 8.4 of EN 1990:2002): 8. Designed effects of actions 46 .1.6. design values of geometrical data (ad) shall either be assessed directly or be derived from nominal values using the following equation ( 6.4.1. Designed values of geometrical data In cases where deviations in the geometrical data have a significant effect on the reliability of a structure. Designed values of geotechnical parameters To determine design value of geotechnical parameter we follow the rule: 8.1.5.3. During the verification of geotechnical strength (i.e. GEO limit state) some effects of the actions will depend on the strength of the ground in addition to the magnitude of the applied action and the dimensions of the structure. Thus, the effect of an action in the GEO limit state is a function of the action, the material properties and the geometrical dimensions. During the verification of static equilibrium (i.e. EQU limit state) some effects of the actions (both destabilising and stabilising) will depend on the strength of the ground in addition to the magnitude of the applied action and the dimensions of the structure. Thus, the effect of an action in the EQU limit state, whether it be a stabilising or a destabilising action, is a function of the action, the material properties and the geometrical dimensions. 8.1.7. EQU EQU: loss of equilibrium of the structure or the supporting ground when considered as a rigid body and where the internal strength of the structure and the ground do not provide resistance. Limit state is satisfied if the sum of the design values of the effects of destabilising actions (Edst;d) is less than or equal to the sum of the design values of the effects of the stabilizing actions (Estb;d) together with any contribution through the resistance of the ground around the structure (Td), 47 8.1.8. GEO GEO: failure or excessive deformation of the ground, where the soil or rock is significant in providing resistance. This limit state is satisfied if the design effect of the actions (Ed) is less than or equal to the design resistance (Rd), 8.1.9. STR STR: failure or excessive deformation of the structure, where the strength of the structural material is significant in providing resistance. As with GEO limit state, the STR limit state is satisfied if the design effect of the actions (Ed) is less than or equal to the design resistance (Rd), There are also UPL and HYD limit states. UPL: This limit state is verified by checking that the sum of the design permanent and variable destabilising vertical actions (Vdst;d) is less than or equal to the sum of the design stabilizing permanent vertical action (Gstb;d) and any additional resistance to uplift (Rd). HYD: This limit state is verified by checking that the design total pore water pressure (udst;d) or seepage force (Sdst;d) at the base of the soil column under investigation is less than or equal to the total vertical stress (sstb;d) at the bottom of the column, or the submerged unit weight (G'stb;d) of the same column. 8.1.10 GEO/STR Limit states 48 Three Design Approaches are offered. The design approach followed reflects whether the safety is applied to the material properties, the actions or the resistances. Design Approach 1: Combination 1: A1 + M1 + R1 †Combination 2: A2 + M2 + R1 Design Approach 2: A1 + M1 + R2 Design Approach 3: A* + M2 + R3 A*: use set A1 on structural actions, set A2 on geotechnical actions † For axially loaded piles, DA1, Combination 2 is: A2 + (M1 or M2) + R4 POLISH NATIONAL ANNEX STATES THAT DESIGN DESIGN APPROACH NR 2 SHALL BE USED 8.2. Retaining wall design 8.2.1. Limit states The limit states are: • loss of overall stability; • failure of a structural element such as a wall, anchorage, wale or strut or failure of the connection between such elements; • combined failure in the ground and in the structural element; • failure by hydraulic heave and piping; • movement of the retaining structure, which may cause collapse or affect the appearance or • efficient use of the structure or nearby structures or services, which rely on it; • unacceptable leakage through or beneath the wall; • unacceptable transport of soil particles through or beneath the wall; • unacceptable change in the ground-water regime. And for : - Gravity walls: • bearing resistance failure of the soil below the base; • failure by sliding at the base; • failure by toppling; - Embedded walls: • failure by rotation or translation of the wall or parts thereof; • failure by lack of vertical equilibrium. 49 EN 1997-1:2004 9.2(1) Examples: 8.2.2. Future unplanned excavation In ultimate limit state calculations in which the stability of a retaining wall depends on the ground resistance in front of the structure, the level of the resisting soil should be lowered below the nominally expected level by an amount Da. — for a cantilever wall, �a should equal 10 % of the wall height above excavation level, limited to a maximum of 0,5 m; — for a supported wall, �a should equal 10 % of the distance between the lowest support and the excavation level, limited to a maximum of 0,5 m. EN 1997-1:2004 9.3.2.2 9. Diaphragm wall calculations 50 Point 2. Calculations will be made for each step of construction process. so danger zone is around 10 meters around the perimeter of construction area.1 In this example following soil parameters are considered: 51 .5 meters measured from the existing ground.00. because of the similarity in the values of partial safety factors. maximum lateral displacements of the wall (Umax) were calculated and compared. Water level for designed area is assumed as at the depth 11. General assumptions for project. Surrounding buildings are in the danger zone. As can be seen from in Annex A2 ( Pictures from the building site) the surrounding buildings are in the danger zone.In this chapter one panel of diaphragm wall will be calculated and designed. normal traffic on streets and so on. There are four retaining walls in the project. Calculations will be performed using following methods: Dependent pressures method. according to Polish Code PN-83/B-03010 Design of retaining walls. It is considered the load distribution angle in soil is 45o. 9. material coefficients and soil resistance (Previous chapters). Representative values of actions were calculated assuming the value of coefficient = 1. Description of calculations. according to PN EN 1990 Basis of structural design. It can me machinery on the construction site. The safety factor for temporary distributed additional load is 1. Analysis were performed determining minimum penetration of the diaphragm wall below the bottom of the excavation (D) and maximum bending moments (Mmax). It is necessary to strengthen the construction or surrounding buildings ( this is not a part of this project) There can be some temporary distributed load right behind the retaining structure. Therefore additional load p=5 kN/m2 (characteristic value) is applied in every calculation.4. The method of calculations will be explained using cut section I as an example. In addition. Design values of actions were calculated applying partial safety factors according to Polish Code (PN) or Eurocode 7. it is possible now to calculate the necessary diaphragm wall. With the vertical cross section of the soil and the characteristics values. Dependent pressures method. as well as First DA (DA1) Calculations employing dependent pressure method were performed using software GEO5 Sheeting check. of Eurocode 7 specifies 3 Design Approaches with combinations of partial safety factors referring to surcharges. Dependent pressures method was chosen because of its simplicity and as it is very common in European and Polish design practice. The geometry of the analyzed case is shown on Figure 9.8 meters. According to Eurocode 7 retaining walls should be designed at limit states (GEO). Calculations will be performed using one combination of partial safety factors from the second Design Approach DA2 (practiced in Poland). according to Eurocode 7.1.5.2. All are designed as diaphragm walls. The method of evaluation of subgrade reaction modulus (kh) based on nomogram of Chaidesson was chosen. Third DA(DA3) was ignored.’ 9. Important information about the project: The deepest excavation is 7. active earth pressure coefficient (Ka).k [kPa] Table : Characteristic values of soil parameters for DA2 9.2 3.31 3.3 16. Designed values.5 0 30.5 0. 52 .7 0.1 2 Fine sand FSa ID=0.5 0 30 0.4 – great depth Characteristics values of: soil parameters.2 saclSi 21 35 20.0 – 1.29 wet 6.0 0. Earth pressure coefficient are taken from ANNEX 7 page 126.4 1.46 2.9 3 Clayey silt saclSi IL=0.2 – 6. passive earth pressure coefficient (Kp) are given below in the table.0 2 Fine sand FSa 3 Clayey silt 4 5 cu.0 – 5.41 2.07 semi dry 2. g[kN/m3] 0 f'k [ ] Ka Kp 0 22 0.3.5 wet 5.5 16.0 Nr Layer Symbol 1 Embankment - 18.31 3.3 Silty sand siSa 17.1 1.2 Clayey silt saclSi 20 28.Nr Layer Symbol Density Humidity Depth Thickness 1 Embankment - Loose wet 0.4 semi dry 1.1 – 2.2 4 Silty sand siSa ID=0.2 5 Clayey silt saclSi IL=0.6 0.48 2. In the DA2 (A1 + M1 + R2 ) partial safety factor for reduction of soil resistance in front of the wall gR = 1.00 kPa C3.k= 18.70 o • C3.00 kPa Soil nr 2 – FSa • γ2.4 will be considered in further calculations.00 ) = 30 o • C2= 0.γ = 21.d =arc(tg f 3.70o f 3.50 kN/m3 • f 2.d= γ2.00/1.00o f 1. Soil nr 1 – Embankment • γ1.k= 16.k / γø)= arc(tg22.k/ γ3.00 ) = 20.50 kN/m3 γ2.0 = 16.d= γ3.d =arc(tg f 1.k= 35.k/ γ1.00 = 35.00 ) = 22.5/1.00 kPa Soil nr 3 – saclSi • γ3.0 = 18.c = 35.0 o • C1= 0.00 kN/m3 • f 3.0 = 21.d= γ1.d =arc(tg f 2.00 kN/m3 • f1.d= C3.00 / 1.00 kPa Soil nr 4 – siSa • γ4.50 kN/m3 53 .00 / 1.k/ γ2.k/ γ3.00 kN/m3 γ1.k = 22.70 / 1.00o f 2.00 kN/m3 γ3.k= 17.k = 20.k= 21.γ = 18/1.0/1.k / γø)= arc(tg30.k = 30.k/γø)= arc(tg20.γ = 16. 50o f 4.g.k/ γø)= arc(tg16.d= γ5.s PHASE 2 Stage 5: excavation to level -7.g.g.50 kN/m3 • f 4.b.s.00 ) = 16.k/ γ4.k/ γ5.55 m. Stage 4: installation of reinforced concrete slab at level -3.30 kPa Following construction stages are considered: Stage 1: excavation to level 0.MANUALLY CALCULATION STATIC MODEL 54 .g.γ4.k/ γø)= arc(tg30.d= C5.s.g.30 kPa C5.d =arc(tg f 5.k= 20.00 m.γ = 17.g.00/1.k = 16.k/ γ5.d= γ4.50 /1.60o f 5.00 kN/m3 • f 5.k = 30.50 o • C4= 0.3 m b.00 = 28.d =arc(tg f 4.0 kN/m3 γ5. PHASE 3 All phases will be calculated by GEO5 software.s.c = 28.00 kPa Soil nr 5 – saclSi • γ5.0 = 17.6 o • C5= 2Sp8.60 /1.50/1.b.γ = 20.b.30/1.s.3 m b.55 m b. PHASE 3 will be calculated manually. PHASE 3 .s. Stage 6: installation of reinforced concrete slab at level -7.00 m.00 ) = 30.0 = 20. Stage 2: installation of reinforced concrete slab at level 0. PHASE 1 Stage 3: excavation to level -3. 10m ( the bottom of the first layer) 55 .2(2)} the designed height of the diaphragm wall (Ho) equals: Active earth pressure from weight of the soils (permament load): characteristic values of active earth pressure : eak designed values of active earth pressure : ead Formulas according to PN EN 1997 .0)= ea.35 = 0 kN/m2 for z=1.3.k. (0. i = γi.d* [kN/m2] for cohesive-less soil for cohesive soil for z= 0.1: eak = γi.0 * γE = 0 *1.46 = 0 kN/m2 ea.0m ( top of the first soil layer) ea.2.0) = 18 * 0 * 0.d.d * z * Kai – 2 * Ci.(0.d * z * Kai [kN/m2] ea.k. k.Designed wall height: According to Eurocode 7 point:{9. 5 kN/m2 for z=2.9) * 0.2) * 0.4) = (18.5*1.0*1. (1.2) * 0.15 *1.2+17.(1.9+21.31 = 31.5*0.k (5.35 = 52.0*1.47 *1.0m (top of the third soil layer) ea.00*3.46 – 2 * 28.5*0.1+16.35 = 14.d(2.2) = (18.58 kN/m2 ea.k.4 m (the bottom of the fourth layer) ea.1 * 0.1 * 0.74*1.k.5*0.k (3.2+17.30 * = 2.k (6.5 m (the bottom of the fifth layer) ea.k (2.12 kN/m2 ea.46 – 2 * 28.29 kN/m2 for z=1.5*1.33 kN/m2 for z=5.ea.1 ) * 0.47kN/m2 ea.(1.00*3.00m ( the bottom of the second layer) ea.9) * 0.5*0.14 kN/m2 ea.74 kN/m2 ea.40 * = 38.00*3.5*0.11 kN/m2 ea.d.5*0.d. (1.01 kN/m2 dla z=5.5) = (18.5*0.35 = 42.35 = 31.14 *1.1) = 18*1.35 = 12.0*1.0*1.1+16.35 = 3.0)= 10.31 = 38.9+21.k (6.52 kN/m2 ea.31 = 6.35 = 19.10m ( top of the second soil layer) ea.(2.4) = (18.46 = 9.2)= 31.30 * = 23.1)= 6.d(3.5 m + t 56 .9+21.1) = 18 * 1.20m ( the bottom of the third layer) ea.2) * 0.2+17.d.1+16.20 m ( top of the fourth soil layer) ea.00*1.52*1.41 kN/m2 dla z=6.2) = (18.9+21.24 kN/m2 for z=7.4) = 14.30 * = 14.0)= 2.12 *1.00*3.5) = 23.k.2 + 20.1) = ea.35 = 51.11 *1.d(6.31 = 10.1+16.14 kN/m2 ea.41 – 2 * 28.9+21.07 kN/m2 dla z=7.2)= 38.0) = (18.35 = 8.00*3.08 *1.4 m (top of the fifth soil layer) ea.0) = (18*1.d(5.1+16.1+16.0*1.k (7.4) = 38.1+16.0*1.2) * 0.64 kN/m2 dla z=6.28 kN/m2 for z=2.08 kN/m2 ea.d(7. (2.1* γE = 9.41 – 2 * 28.5*1.d(6.58 *1.k. 00 *(t + 1.5 +t) = 14.d (7. that means that 7.IMPORTANT : t is the dimension of the wall under the excavation level.41 * 20.1) = 8.k )we assume static model with one strut : Graph 1.12 + 1.5 +t) = 14.2 t + 31.k (7.5 m +t = total height of the wall.24 kN/m2 To calculate the resultant value of active earth pressure from permanent load (RBg.1) = 8.2 t + 23.41 * 20. ea.12 + 0.00 *(t + 1. Active soil pressure from permament load 57 .35 *0.14 kN/m2 ea. 5*9.2 * 1.8 kN/m2 In third soil layer: eakn.6 * 1.48 = 57.2 = 120 * 0.14)-14.2*0.5t)) + (2.1)*(3.76t2 + 139.49t3 + 52.5 = 82.6 kN/m2 eadn.71) Active earth pressure from weight of the surrounding buildings and machines (temporary load): load from the surrounding buildings = 115 kN/m2 load from the machines = 5 kN/m2 Total temporary load = 120 kN/m2 characteristic value of active earth pressure : eakn designed value of active earth pressure : eadn Formula according to PN EN 1997 .12)*(t+1.2 * 1.2t+23.5t) +(((8.2 kN/m2 eadn.3 = 55.31 = 37.4)+((38.1 = 120 * 0.74-6.9*1.31 = 37.14*0.2 = 37.66) – (6.5t) = 185.08-31.58*1.73)+(31.4 = 37.5 = 86.46 = 55.6+0.49t3 the resultant value of active earth pressure from permanent load RBgk = (5.1+0.8 kN/m2 In fourth soil layer: eakn.2*0.2 kN/m2 eadn.5 = 55.19t + 52.2*0.14)*0.1 = 57.85) – ((10.47*3.1*0.2 * 1.5*0.5*2.5*0.4 = 120 * 0.5 = 55.19t + 185.8 kN/m2 58 .6) +(14.2 kN/m2 eadn.1*2.3 = 120 * 0.58)*1.1+0.76t2 + 5.2*2.11*1.1)*(4.9*1.71 + 139.52-2.47)*3.4 kN/m2 In second soil layer: eakn.7) – (RBgk * (4.2)+((38.67t) = 0 RBgk * (4.1: eakn = pk* Kai [kN/m2] In first soil layer: eakn.-(0.12*(t+1. In fifth soil layer eakn.2 * 1.2 kN/m2 eadn.8 kN/m2 Graph 2.5 = 120 * 0.5 = 49.5 = 73.41 = 49. Active soil pressure from temporary load 59 . 0)0.k+eph1.05t+20t2 Determination of requirement anchorage length “t” Model: 60 . Ka.30*(2. because of the high depth of ground water level (.30 kPa .0 kN/m3 . f 5.41.k = 16.k= 20.k=(eph1.k=2*28.5 = 2.k)*0.0*20. Passive earth pressure from weight of the soil layers (permanent load): Formula according to PN EN 1997 .04 kN/m2 eph2.Water pressure was ignored. Kp.04= 40t+80. C= 28.k=2.11 m GWL).k=Kph (γ*z +p)+2ck(Kph )0.04 Eph.0 eph1.0*t+80.1: eph.5 = 0.60o .5=80.5t=80.5 where p=0 For fifth soil layer (saclSi) following parameters are assumed: γ5. 5 F(t) = 7.46 Assumed value t=2. assumed value should be increased by: t’= 2.29 t=2.8m.5 gW= 1. because of the high depth of ground water level (.d = Rbg.11 m GWL).w* gW was ignored.8 m + ∆hn=2.83 t=2.4 RBp.2 m Checking the compatibility between earth pressure and wall displacement The scheme of wall displacement is shown in picture below : 61 .To find dimension 't' formula according to PN EN 1997 – 1 is used: RB.5= 3.k* gQ + RBp.8 F(t) = 0.k / gR According to DA2: gG = 1. According to Eurocode PN EN 1997-1.10 t=3 F(t) = -4.w* gW < Eph. Formula above assumes the form: Using Mathcad software 't' is searched by method of successive approximations : t=2 F(t) = 18.k* gG + RBp.d < Eph.d For Second Designed Approach (DA2) the formula assumes the form : RB.35 gQ = 1.8+0.9 F(t) = -2.25 t=2. 3 m Referring to obtain parameters: ρA=0.5*0.0073 For soils.scheme of wall displacement According to PN-83/B-03010 Designing of retaining wall formule nr 20 : [Annex 9] f=ρp.04/(410+280)=0.072*280)/2=5.60o and for : t = 2.50o and for: h = 10.k = 16.7 – 3.gr*t/2=0.5ρp*t/2 According to PN-83/B-03010 graph nr 9 : for: f 5.0073 > ρa=0. appearing behind the wall according to graph 8 PN-83/B-03010: for: f = 30.8 m f=(0. Determination of earth pressures for total length of the wall : 62 .04 mm The minimum value of the wall displacement in relation to the soil behind the wall: ρA=5.002 CONCLUSION Wall anchorage length can be considered as sufficient.4 = 7. 4 = 148.2 + 23.2 m ea. that gives the total length of diaphragm wall equals 10.d (6.2) (5.19*3.5 m + 3.71) = 183.1+0.38 kN/m2 ea.d=208.2)(24.35 = 247.04=208.4 +3.2 *3.34 kN/m RBgd = 183.38 * 1.5 kN/m Graphs of the eart active and passive pressures are given below.34 * 1.k= 40t+80.18*3.4 +3.2) = 8.2) = 49.6*3. 63 .22 + 204.15 kN/m Reaction from active earth pressure from permanent load RBgk = 1/(4. Active earth pressure from weight of the soil layers (permanent load) at level z=7.5 = 264.2 m under the excavation level eph2.95) = 176.7 m.Requirement anchorage length “t” is assumed as 3.2+80.49*3.6 kN/m2 Reaction from active pressure from temporary load RBpk = 1/(4.1+0.2 + 97.22 + 139.01 kN/m RBpd = 176.01 * 1.35 = 66.23 + 52.5*3.04=40*3.k (6.2 m according to previous calculations.04 kN/m2 eph2.2 + 185.04/1.76*3.66 kN/m2 Passive earth pressure from weight of the soil layers (permanent load) at level z=3.14 = 49.5*3. Active and passive soil pressures .Graph 3.characteristic values (from temporary and permanent loads) 64 . Graph 4.designed values (from temporary and permanent loads) Determination the resultant pressure under the excavation level 65 . Active and passive soil pressures . 87 kN/m2 At the bottom level of excavation .5*C earth active pressure from the weight of the soil at the bottom level of excavation: ea.8 + 31. 148.04 / 1.2 m under the excavation level.47. K*u= ed – 0.d (7.47.9+21.0*1.00*3.14 * 1.87 kN/m2 ('-' in this case means the active pressure) Resultant earth pressure value at the depth of -3.24 ) = .8 + 66. the resultant earth pressure on the wall equlas 8.17 .2 kN/m2 ea.h1k = 80.4 = 57.14 kN/m2 ea.2 kN/m2 ('+' in this case means the passive pressure) 66 .5*0.5) = (18.d2 (7.(73.5) = 49.k2 (7. the resultant earth pressure on the wall equals .6 ) = 8.5 = 73.2 * 1.5*1.k (7.04 kN/m2 ep.2 kN/m2 At a depth of 3.h1 d = 80.1) * 0.24 kN/m2 earth active pressure from the temporary load at the bottom level of excavation: ea.2+20.5) = 49.30 * = 23.41 – 2 * 28.2 m under the excavation level .5) = 23.K*=(Kp-Ka)*g.1+16.(73.6 .2+17.17 kN/m2 Resultant pressure at the bottom level of the excavation ed = 57.00*1.8 kN/m2 earth passive pressure from the weight of the soil at the bottom level of excavation: ep.35 = 31. Resultant values of earth pressures .characteristic values 67 .Graph 5. Resultant values of earth pressures .designed values 68 .Graph 6. According to the graph . Determination of resultant forces of active and passive earth pressures (designed values) The graph of results from the table above is given on page 70. the Ra force can be determined from thr scheme: 69 .Location of '0' point (where resultant of passive and active earth pressure equals zero) According to the graph 6 'u' value (zero point) is assumed at the depth of 2.7 m under the excavation level. Graph 7.designed values 70 . Resultant forces of earth pressures . 85 . Resultant forces of earth pressures .39 – 108.45 – 353. according to locations of resultant forces.92 + Ra = 0 Ra = 718. -101. Shear forces 71 .50 – 123. all parameters were introduced to the mathematical software RM-WIN (Polish engineering software) to obtain the graphs: Graph 8.8 kN The diaphragm wall was divided into 9 sections. Then.79 – 60.designed values y = 0.Determination of reactions According to: Graph 7.62 + 96.64. 39*2. The maximum bending moment manually calculated according to graph 7: Mmax1= .506 kN and the maximum bending moment -401.45*1.85) . the software gives the normal forces. 585 kNm.98 + 1.401.21 +0.79 * (0. Bending moments In addition to making graphs. shear forces and bending moments.60.32 + 1.101.2) = .2 +123. 72 .41 + 108. All parameters are given in the table: The maximum shear force according to table from software equals 555.85 + 353.50*0.07+2.5* (1.98+1.015.07 + 2. The manually calculation can be considered as correct.96.Graph 9.85* (1.6 kNm The difference between bending moments from manually calculation and software calculation equals 0.41) . 64.57 .57) . Ra*3.05 – 0.2 – 0.64 * (3.2) + 80.2 ) .21 +0. -18.87 +7.37.35 + Rb * 3.2 Rb Rb = -1.95 = 0 Ra = 1.57 + 0.82 * (1.98 + 2.82 * (1.2) – 80.66 * (0.51 * (0.05 + 2.5 + 1.21 + 2.0.98 + 0.18.51 * (3.2 – 2.98 + 0.05 + 0.57 .21 +0.2 .0.98 + 2.88 73 .98) – 121.36 * (2.57) + RC *7.29 Rc MB = 0.57 + 0.8* (0.64 * 0.23 Rc .2 = 0 3.57 – 16.36 * (2. To calculate the diaphragm wall in 5.07 +2.2) – 121.98 +0.35 Rc = .8 * (2.21) – 37.16.2 + 0. First step is to find the relations between different reactions: MA = 0.2 .21 + 2.57 – 0.21 + 0.07 +2.66 * 0.3.2) -64.05 + 0.07 +2.07 + 2.The method of calculation diaphragm wall with one strut is already known.2) – Rc * 3.phase (with 3 struts) we have to only change the static model and add two additional reactions.5 + 1. 64 * (3.2 + 3.80 kN Ra = .81 Ra + 395.36 * 2.64 . Graph 10.79 Using relations between different reactions it is possible to find the values of forces: -1.80.95 +Ra * 7.51 .MC = 0.1 + 80. but more complicate due to number of unknown reactions.82 * 0.95) + 16.37.23* -76.82 .29 Rc = 1.36 + Rc +Rb +Ra = 0 Rc = -Rb – Ra + 339.21 + 1.23 Rc – 175) + 191.80 – 88 Ra = .66 * (2.2 – 2.81 Ra + 395.2 X = 0.23 Rc – 88 = 1.15 = 0 Rb = 1. 18.16.07 + 37.5 + Rb*3.81(1.8 * 1.64.07) 64.66 . -18.121.6.05 + 2. Shear forces Graph 11.2 Rb = 465.1.51 * (2.8 .4 kN Then.07) + 121. all parameters are introduced to the mathematical software RM-WIN to obtain the graphs.04 kN Rb = 1.31 Rc = -76. The method of calculation are analogous to previous ones.21 + 1. Bending moments 74 . 97 kNm Max.93 kN/m Max.2 mm PHASE 2 Max.displacement 4.46 kN/m Max.47 kNm Max.8 kNm Max.displacement 8.35 kN/m Max.20 kNm Max. bending moment 828. shear force 161. shear force 513.6 mm PHASE 3 Max. shear force 531.3.5 mm PHASE 4 Max.61 kN/m 75 . shear force 351. bending moment 537.0 mm PHASE 5 Max. bending moment 508.displacement 18.7 m − thickness of diaphragm wall h = 80 cm − Struts: fixed Results: PHASE 1 Max. Geo 5 calculations Assumptions for Geo5 software: − calculation according to PN EN 1997:1 − Design Approach 2* − Active earth pressure according to: Coulomb − Passive earth pressure according to: Caqout – Kerisel − Methods for the evaluation of the modulus of subsoil reaction: Chadeisson − water level and soils then same as for manual calculation − height of the construction 10. shear force 546. bending moment 864.90 kN/m Max.9.displacement 1. 42 kNm Max.4.Max.8 kNm.5*40=92 mm d = h-a d= 80 – 9.80 m Total height of the wall H=10.33 MPa Ecm=32 GPa Calculations: cover: a=c+∆c+�1+0.displacement 3. construction �2= 40 mm fctd=1.8 cm Reinforcement As1 According to Eurocode 2 (PN EN 1992-1-1) following formula is used: where Msd is maximum bending moment 76 .05m Concrete class C30/37 Steel AI. so phase nr 3 of construction process is decisive. The maximum bending moment in this case is 864.6 mm 9.7 m Ribs cover c=0. Determination of reinforcement The reinforcement will be designed according to maximum bending moment. bending moment 861. Assumptions: Thickness h=0.5*�2 a = 50+10+12+0. St3Sx.2 cm = 70. fyd =210 MPa Steel AIII-RB400W fyd = 350 MPa Assumed reinforcement : horizontal �1= 12 mm. In this project diaphragm walls are mostly made of panels that are 750 cm length.59 cm2 is a reinforcement that we need for 1 linear meter of wall.Determination of minimal reinforcement As1 According to Eurocode 2 (PN EN 1992-1-1) following formulas are used: According to Eurocode 2 (PN EN 1992-1-1) following parameters are assumed: The results are given below: Assumed reinforcement : The value 85. Required reinforcement for 750cm length panel is: 77 . 4000x14 = 56000 ZL 395x1200 = 474000ZL 78 . The mud costs 50 ZL/m3. At the beginning of the excavation a cycle is quick. for this panel it can be assumed 34 ϕ 40 in 15 cm ( As1=427. Finally to excavate 1198. that equals 119 hours (10 days when the work day = 12 hours).4 m 3.12 cm2 All dimensions of panels are given in the Drawing nr 2 (Annexes with drawings) There is one panel that has 1000 cm length.11 cm2 .5=642. It bucket has a capacity of 1.70 m =1198.59 *5.As1=85. Duration and prices Duration For the duration of the implementation of the diaphragm wall all the quantities have to be detailed. This panel probably will be split in 2 shorter panels . About 5 people are needed. It gives a result of 7190 minutes. Steel fixer and people to help take around 100 ZL /day.80 m * 10. It is the same amount of mud than concrete. 10.59 *7. The concrete costs 395 ZL/m3.0=427. this price includes the reinforcement.16 cm2) Reinforce of the panel 500 cm is shown in DRAWING NR 4.7 cycles. For all walls. Required reinforcement for 750cm length panel is: As1=85.500 cm per each one. Other walls haven't been calculated but the total height of each one will be assumed as 1070 cm too. For additional materials 200 ZL/m3 can be assumed. The total amount of concrete is approximately 1200m3 . the hydraulic grab will have to excavate : (40m +40m+ 30m +30m)* 0.4m 3. The detailed dimensions of one diaphragm wall are known from previous calculations (wall in cut section I : 4000 cm length x 80 cm thickness x 1070 cm height). but when the hydraulic grab has to go down to 7 meters it takes much more time. around 2 weeks is needed.2m3. Price The hydraulic grab will cost 4000 zlotys (Polish currency) per one day. The duration of a cycle is around 6 minutes (Information from website). around 200m of other materials. The grad will have 998. 2 weeks are needed to create the diaphragm walls. 200x200 = 40000ZL 50x1200 = 6000 ZL 5x100x14 = 7000ZL The global price : 56000+474000+40000+6000+7000 =583000 ZL = 1 166 000Dkk 79 . Before digging any excavations. Wear a hard hat when working in excavations People and vehicles falling into excavations: Take steps to prevent people falling into excavations. use stop blocks to prevent them from over-running. Materials falling into excavations It is not recommended to store spoil or other materials close to the sides of excavations. If the excavation is 2 m or more deep. fumes. Every year. Remember that the sides of the excavation may need extra support. Safety and organization the building site. props. It is recommended to make sure the edges of the excavation are protected against falling materials. supervised and carried out to prevent accidents. Surveys of the foundations and the advice of a structural engineer may be needed. Avoiding underground services: 80 .11. provide substantial barriers. etc. It is necessary to make sure the necessary equipment needed such as trench sheets. The spoil may fall into the excavation and the extra loading will make the sides more prone to collapse. Where vehicles have to tip materials into excavations. people and vehicles falling into the excavation. Keep vehicles away from excavations wherever possible. contact with underground services. is available on site before work starts. Undermining nearby structures Make sure excavations do not affect the footings of scaffolds or the foundations of nearby structures. Where this is not possible use safe systems of work to prevent people being struck. access to the excavation. baulks. Use brightly painted baulks or barriers where necessary. Plant operators should be competent. eg guard rails and toe boards. it is important to plan against the following: collapse of the sides. People being struck by plant: Keep workers separate from moving plant such as excavators. Provide toe boards where necessary. Decide if the structure needs temporary support before digging starts. managed. people being struck by plant.1. accidents to members of the public. Walls may have very shallow foundations which can be undermined by even small trenches. people are killed or seriously injured when working in excavations. undermining nearby structures. materials falling onto people working in the excavation.. Excavation work has to be properly planned. Safety and organization 11. There are four different methods to control the groundwater table in connection with a building or construction project: * Water is allowed to seep into the excavation and is removed by bilge pumping (possibly with drain) * A temporary or permanent dewatering is established. This is the simplest and cheapest form of groundwater draw-down. freezing. For this project the dewatering of the excavation will be done by simple drainage. Do not site petrol or diesel-engined equipment such as generators or compressors in. eg valve covers or patching of the road surface.5 meters below the excavation level. Dewatering should then be arranged so that the water table is lowered at least 0. for instance in tunnels and caissons.at the start of each shift before work begins. earth or other material. alteration or removal of excavation support. Temporary dewatering For the excavation it is necessary to perform a temporary dewatering. Mark the ground accordingly. injection * The water pressure is withheld with air pressure.It is recommend to : look around for obvious signs of underground services. Inspecting excavations A competent person must inspect excavations: . Make sure that the person supervising excavation work has service plans and knows how to use them. 81 . or near the edge of.after any event likely to have affected the strength or stability of the excavation. Supervision A competent person must supervise the installation. . Access It is recommend to provide good ladder access or other safe ways of getting in and out of the excavation. slot walls. Protecting the public Fence off all excavations in public places to prevent pedestrians and vehicles falling into them. take precautions (eg backfilling or securely covering excavations) to reduce the chance of them being injured. whereby the groundwater table is drawn down to below the construction/excavation level * The groundwater movement is cut off with tight walls. an excavation unless fumes can be ducted away or the area can be ventilated. Everyone carrying out the work should know about safe digging practices and emergency procedures. for example sheet pile walls. Where children might get onto a site out of hours. 11. Fumes Exhaust fumes can be dangerous. from the bottom of the excavation and rejects excessive water to another place. which consists of pumping water with a system of drains. . Use locators to trace any services.after any accidental fall of rock. People working in excavations should be given clear instructions on how to work safely.2. For dewatering. The main reason was the proximity to other existing buildings. Geological and geotechnical analysis were made at first.12. According to assumed soil layers and water level in the area. Calculations for dimensioning the walls were made in two different ways: by hand and Polish engineering software RM WIN. the estimation of the price and of the duration were done. Conclusion This project was about excavation works for Skyscraper in Wroclaw (Poland) . The Polish way to calculate the structural element are probably different from the Danish way but thanks to the Eurocodes we are going to move to a standardization of the construction rules to make the international projects as that one more accessible to European companies. all calculations have been done. Calculation methods and equations are found mainly from study materials from Polish geotechnic' books . An important issue of this project was determination of retaining structures. the aim was to provided to Danish companies an idea about how the other European countries (in this case:Poland) work and how they design foundations. and by GEO 5 . The best solutions for Skyscraper occurred top and down method – very fast one. Deep excavations in urban areas require retaining structures to ensure the slopes and protect surrounding buildings. For all sides of the constructions site. The next step was to find proper type of diaphragm wall (in this case: strutted method ) and to analyze deep excavation methods. The designed elements are relevant to be able to start the construction and the drawing provide an easy way to build the structure – diaphragm walls. because it is suitable in clay soils. Calculations were made by using safety factors from relevant parts of Eurocode 7 and some Polish Standards. 82 . the best solution diaphragm walls – were chosen. To conclude. the method called „Simple Drainage“ was selected. Because the foundations have been designed using Polish methods and Standards. Maj .. Seminarium GŁĘBOKIE WYKOPY NA TERENACH WIELKOMIEJSKICH. Instytut Techniki Budowlanej.B Yurkevivh. Projektowanie geotechniczne według Eurokodu 7. [5] Siemińska-Lewandowska A. wydanie 7. [8] Rychlewski P. DEVELOPMENT TOP-DOWN METHOD OF UNDERGROUND CONSTRUCTION OR HI-TECH IN RUSSIAN. Ochrona zabudowy w sąsiedztwie głębokich wykopów. Ścigałło J.emails COURSES AT WARSAW UNIVERSITY OF TECHNOLOGY Bsc of Civil Engineering with specialization : geotechnics BOOKS AND LITERATURE [1] Wysokiński L.. cz. GEOINŻYNERIA drogi mosty tunele 04/2005 (07) [10] Krasiński A. Problemy budowy głębokich podziemi budynków użyteczności publicznej. Instytut Badawczy Dróg i Mostów. Kłosiński B. Problemy projektowe wymiarowania głębokich budowli podziemnych. Nowoczesne Budownictwo Inżynieryjne.2008 [6] Siemińska-Lewandowska A. Grzegorzewicz K. Design of deep excavations according to Eurocode 7. Głębokie wykopy w zabudowie miejskiej. [11] Warunki techniczne wykonywania ścian szczelinowych.. Instrukcje zeszyt nr 35 Warszawa 1992. [13] Pisarczyk S. Geologii i Budownictwa Morskiego.Kwiecień 2010. Russian Federation STANDARDS: [15] PN – EN 1538:2002 Wykonawstwo specjalnych robót geotechnicznych. [14] P. References CONSULTATIONS WITH LECTURERS Consultations with Sara Elisabeth Kjærgaard . warszawa 1999. Marzec . Kotlicki W. Mechanika gruntów. Zarys geotechniki.. Katedra Geotechniki. XXX. Warszawa 19 listopada 2011 [3] Kotlicki W. Warszawa 2011 [2] Kłosiński B. No.. Oficyna Wydawnicza Politechniki Warszawskiej.. Ściany szczelinowe [16] PN . Godlewski T. Vol.. Wydawnictwo ITB nr 376/2002. Yurkevich Engineering Bureau ltd. Aktualne problemy budowy i projektowania głębokich wykopów. 12. Konferencja Naukowa „KRYNICA 2003”. Informacje... Aktualne problemy budowy i projektowania głębokich wykopów. [12] Wiłun Z. Studia Geotechnica et Mechanica. Moscow. Mitew-Czajewska M. cz. GEOINŻYNERIA drogi mosty tunele 03/2006 (10) [9] Florkiewicz A. Projektowanie obudów głębokich wykopów. Wydawnictwa Komunikacji i Łączności.1. Wydział Inżynierii Lądowej i Środowiska Politechniki Gdańskiej.2. wydanie III. Warszawa 2005. Obliczanie i projektowanie ścianek szczelnych. Warsaw University of Technology.. Część 1:Zasady ogólne 83 .13.EN 1997 -1:2008 Eurokod 7 Projektowanie geotechniczne. Wysokiński L.. Nowoczesne Budownictwo Inżynieryjne. [4] Siemińska-Lewandowska A.. Gdańsk 2007... [7] Siemińska-Lewandowska A.Czerwiec 2010. posadowienie bezpośrednie budowli. Część 1:Zasady ogólne [19] PN-81 B-03020 „Grunty budowlane.keller.com. obliczenia statyczne i projektowanie” WEBSITES: [20] http://www.uk [22] http://www.com [23] http://www.[17] PN – EN 1997-1:2008/AC:2008 Eurokod 7 Projektowanie geotechniczne.pl [25] http://www.docstoc.com [24] http://www.skycrapercity.diaphragmwallconstruction.com SOFTWARES: [26] GEO 5 [27] RM-WIN [38] Autocad 2009 [29] MS Office 84 .bacsol.au [21] http://www. Część 1:Zasady ogólne [18] PN – EN 1997-1:2008/Apl:2010 Eurokod 7 Projektowanie geotechniczne.menardbachy.co. 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