BGA – TOURING LECTURE – NOVEMBRE 2010ISSMGE Concept and Parameters related to ground improvement illustrated by Case Histories by Serge VARAKSIN Chairman T.C. Ground Improvement (TC 211) 1 State of the Art Report 17TH International Conference on Soil Mechanics & Geotechnical Engineering State of the Art Report Construction Processes Procédés de Construction Jian Chu Nanyang Technological University, Singapore Serge Varaksin Menard, France Ulrich Klotz Zublin International GmbH, Germany Patrick Mengé Dredging International n.v., DEME, Belgium Alexandria, Egypt 5-9 October 2009 NOTA : TC 17 meeting ground improvement – 07/10/2009 Website : www.bbri.be/go/tc17 BGA Touring lectures 2010 Category A. Ground improvement without admixtures in non-cohesive soils or fill materials Method A1. Dynamic compaction A2. Vibrocompaction A3. Explosive compaction A4. Electric pulse compaction A5. Surface compaction (including rapid impact compaction). B1. Replacement/displacement (including load reduction using light weight materials) B2. Preloading using fill (including the use of vertical drains) B3. Preloading using vacuum (including combined fill and vacuum) B4. Dynamic consolidation with enhanced drainage (including the use of vacuum) B5. Electro-osmosis or electro-kinetic consolidation B6. Thermal stabilisation using heating or freezing B7. Hydro-blasting compaction B. Ground improvement without admixtures in cohesive soils Principle Densification of granular soil by dropping a heavy weight from air onto ground. Densification of granular soil using a vibratory probe inserted into ground. Shock waves and vibrations are generated by blasting to cause granular soil ground to settle through liquefaction or compaction. Densification of granular soil using the shock waves and energy generated by electric pulse under ultra-high voltage. Compaction of fill or ground at the surface or shallow depth using a variety of compaction machines. Remove bad soil by excavation or displacement and replace it by good soil or rocks. Some light weight materials may be used as backfill to reduce the load or earth pressure. Fill is applied and removed to pre-consolidate compressible soil so that its compressibility will be much reduced when future loads are applied. Vacuum pressure of up to 90 kPa is used to pre-consolidate compressible soil so that its compressibility will be much reduced when future loads are applied. Similar to dynamic compaction except vertical or horizontal drains (or together with vacuum) are used to dissipate pore pressures generated in soil during compaction. DC current causes water in soil or solutions to flow from anodes to cathodes which are installed in soil. Change the physical or mechanical properties of soil permanently or temporarily by heating or freezing the soil. Collapsible soil (loess) is compacted by a combined wetting and deep explosion action along a borehole. BGA Touring lectures 2010 Sand is fed into ground through a casing pipe and compacted by either vibration. rigid or semi-rigid columns/inclusions and geosynthetic girds to enhance the stability and reduce the settlement of embankments. Sand is fed into a closed bottom geotextile lined cylindrical hole to form a column. Geotextile confined columns C5. Use of piles. Ground improvement with admixtures or inclusions C2. gravel. Rigid inclusions (or composite foundation. fine-grained soil and back filled with densely compacted gravel or sand to form columns. stones or demolition debris. Microbial methods C8 Other methods Hole jetted into soft. Dynamic replacement C3. also see Table 5) C6. rigid or semi-rigid bodies or columns which are either premade or formed in-situ to strengthen soft ground. Use of piles. Unconventional methods. such as formation of sand piles using blasting and the use of bamboo. The backfill can be either sand. or static excitation to form columns. Geosynthetic reinforced column or pile supported embankment C7. Use of microbial materials to modify soil to increase its strength or reduce its permeability. Sand compaction piles C4.C1. dynamic impact. timber and other natural products. BGA Touring lectures 2010 . Aggregates are driven into soil by high energy dynamic impact to form columns. Vibro replacement or stone columns C. Medium to high viscosity particulate suspensions is injected into the ground between a subsurface excavation and a structure in order to negate or reduce settlement of the structure due to ongoing excavation. BGA Touring lectures 2010 . Ground improvement with grouting type admixtures D2. foundations. Compaction grouting D6. Compensation grouting E1. Use of the roots of vegetation for stability of slopes. Biological methods using vegetation E. Earth reinforcement g Solutions of two or more chemicals react in soil pores to form a gel or a solid precipitate to either increase the strength or reduce the permeability of soil or ground. Use of the tensile strength of embedded nails or anchors to enhance the stability of slopes or retaining walls. Chemical grouting D3. Jet grouting D5. Use of the tensile strength of various steel or geosynthetic materials to enhance the shear strength of soil and stability of roads. Geosynthetics or mechanically stabilised earth (MSE) E2. or retaining walls. slopes. embankments. Treat the weak soil by mixing it with cement. or other binders in-situ using a mixing machine or before placement High speed jets at depth erode the soil and inject grout to form columns or panels Very stiff.D. lime. Ground anchors or soil nails E3. Mixing methods (including premixing or deep mixing) D4. mortar-like grout is injected into discrete soil zones and remains in a homogenous mass so as to densify loose soil or lift settled ground. Laboratory Engineering Properties Why Soil improvement ? •To increase bearing capacity and stability (avoid failure) •To reduce post construction settlements • To reduce liquefaction risk (sismic area) Advantages / classical solutions • avoid deep foundation (price reduction also on structure work like slab on pile) • avoid soil replacement • save time •Avoid to change site •Save money ! BGA Touring lectures 2010 . Soil Improvement Techniques Without added materials Cohesive soil Peat . clay … 1 Drainage 2 VAcuum With added materials 4 Dynamic replacement 5 Stone columns 6 CMC 7 Jet Grouting 8 Cement Mixing Soil with friction Sand . fill 3 Dynamic consolidation 4 Vibroflottation BGA Touring lectures 2010 . blocks ? .Water content.Parameters For Concept -Soil caracteristics -cohesive or non cohesive . water table position .Organic materials -Soil thickness -Structure to support -Isolated or uniform load -Deformability -Site environment -Close to existing structure -Height constraints -Time available to build BGA Touring lectures 2010 . Preloading with vertical drains high fines contents soils σ=σ’+u BGA Touring lectures 2010 . Radial and Vertical consolidation BGA Touring lectures 2010 . PVC vertical drain + geotextile BGA Touring lectures 2010 .Vertical drains: material High fines contents soils Flat drain circular drain 5 cm . Vertical Drains BGA Touring lectures 2010 . CR. Cα. CV.Vertical drains CONCEPT -Stable subsoil for surcharge -Soil can be penetrated -Time available is short -Some residual settlement is allowed 1 – Depth PARAMETERS 2 – Drainage path 3 – Cohesion 4 – Consolidation parameters (oedometer. CC. CPT dissipation test BGA Touring lectures 2010 . t. CPT) eO. COGNON PATENT) BGA Touring lectures 2010 .M.Vacuum Consolidation (high fines contents soils) VACUUM (J. CPT) eO. CV. t. Cα. CR.Vacuum Consolidation CONCEPT -Soil is too soft for surcharge -Time does not allow for step loading -Surcharge soil not available -Available area does not allow for berns 1– 2– 3– 4– 56– 7- PARAMETERS Depth Drainage path Condition of impervious soil Watertable near surface Absence of pervious continuous layer Cohesion Consolidation parameters (oedometer. CPT dissipation test Theoretical depression value Field coefficient vacuum Reach consolidation to effective pressure in every layer Target approach 8– 9– 10 – 11 – BGA Touring lectures 2010 . CC. Hamburg BGA Touring lectures 2010 .Case history – EADS Airbus Plant. Hamburg General overview of Airbus site BGA Touring lectures 2010 .Case history – EADS Airbus Plant. 5 m Settlement ≥ 2.5 month and to + 9.5 m Dyke construction to +6.84 m Columns GCC Settlement 0.00 in 16 month Columns GCC Settlement 0.5 in 8.5 month and to + 9.Basic design and alternate concept of Moebius–Menard Temporary sheet pile wall – in 5 month – dyke construction in 3 years Settlement ≥ 2.0 – 5.00 in 16 month Dyke construction to +6.0 – 5.5 in 8.7 – 1.84 m BGA Touring lectures 2010 .7 – 1. Subsoil characteristics BGA Touring lectures 2010 . Hamburg How to move on the mud ! BGA Touring lectures 2010 .Case history – EADS Airbus Plant. Hamburg BGA Touring lectures 2010 .Case history – EADS Airbus Plant. Case history – EADS Airbus Plant. Hamburg BGA Touring lectures 2010 . BGA Touring lectures 2010 .PORT OF BRISBANE – PADDOCK S3B PROJECT OVERVIEW Port of Brisbane Sydney 1000 km Located at the mouth of the Brisbane river. New reclamation area: 234 ha enclosed in the Port Expansion Seawall. Seawall construction completed in 2005. Part of the new reclaimed area to be ready in 5years. PORT OF BRISBANE – PADDOCK S3B GEOTECHNICAL LONG SECTION BGA Touring lectures 2010 . 3 Upper Holocene Clay 0.3 Lower Holocene Clay 0.25 BGA Touring lectures 2010 .008 16 10 10 20 0.9 1.0076 16 0.18 0.2 Parameter Cc/(1+e0) Cα/(1+e0) γ Cv Ch Su Su / σ’v Unit [-] [-] [kN/m3] [m²/y] [m²/y] [kPa] [-] Dredged Material 0.0059 14 1 1 4 0.235 0.8 28 0.235 0.001 19 10 10 0.PORT OF BRISBANE – PADDOCK S3B GEOLOGICAL PARAMETERS Upper Holocene Sand 0.01 0. PORT OF BRISBANE – PADDOCK S3B GEOLOGICAL SOIL PROFILE BGA Touring lectures 2010 PORT OF BRISBANE – PADDOCK S3B DESIGN CRITERIA & ASSUMPTIONS Service Load: Zone 1: Zone 2: Zone 3: Zone 4: 36kPa 25kPa 15kPa 5kPa VC2A VC2B VC4 ROAD CORRIDOR VC3A VC3B VC8 VC5 VC6 Residual Settlement (20y): Zone 1 to 3: 150mm Zone 4: 300mm Vacuum pumping operation: 18 months Vacuum depressure: 75.0 kPa VC1 VC7 BGA Touring lectures 2010 PORT OF BRISBANE – PADDOCK S3B DESK STUDY – NUMERICAL ANALYSIS USING EXCEL SPREADSHEET SETTLEMENT CALC.XLC Calculation of primary and secondary settlement; Secondary settlement to commence after primary settlement; Change in vertical stress is constant over the depth of the stratum; Buoyancy effect on the fill below the groundwater level due to settlement Fill to be removed instantaneous at the end of preloading period; Design load immediately applied at end of preloading period; BGA Touring lectures 2010 Effect of smear due to mandrel insertion output Settlement / Fill thickness chart Graphical BGA Touring lectures 2010 . MD88-3.PORT OF BRISBANE – PADDOCK S3B DESK STUDY… Up Up to 15 surcharge steps. to 30 soil layers. Different Calculation types of drains available: MCD 34. FD767. of shear strength increase during consolidation of cohesive soils. PORT OF BRISBANE – PADDOCK S3B ANALYSIS METHOD Settlement Program uses a method based on Bjerrum’s concept to calculate instantaneous and delayed consolidation (Bjerrum. Secondary eo Initial Stress σ’o Service Load σ’o+Δσ’f Consolidation Load σ’o+Δσ’pxU% Δlogσ’ e1 Primary Consolidation (Pore Pressure Dissipation) ΔH primary H t=1d e2 = ⎛ σ 'o + Δσ final ' ⎞ Cc ⎟ log⎜ ⎜ ⎟ 1 + eo σ 'o ⎝ ⎠ e3 t=To Δe t=To+20y Void Ratio Secondary Consolidation (Long term Creep) ⎛ 20 years ⎞ ⎟ Δe = Cα e log⎜ ⎜ T ⎟ p ⎝ ⎠ BGA Touring lectures 2010 . 1967). PORT OF BRISBANE – PADDOCK S3B CONSTRUCTION SEQUENCE 1ST 2ND SURCHARGE SURCHARGE PLACEMENT PLACEMENT VACUUM UNITS VACUUM UNITS SEALING TRENCH BY BENTONITE MEMBRANE HDPE 1mm VERTICAL TRANSMISSION PROTECTION FILL HORIZONTAL TRANSMISSION PIPES INSTALLATION PIPES INSTALLATION PERMEABL E LAYER VERTICAL MEMBRANE SOIL BENTONITE CUT-OFF WALL Impermeable Strata BGA Touring lectures 2010 . PORT OF BRISBANE – PADDOCK S3B TYPICAL SBW CONSTRUCTION – LONG SECTION Wheeled frame Inner frame Full roll of liner BGA Touring lectures 2010 . PORT OF BRISBANE – PADDOCK S3B BGA Touring lectures 2010 . overlapping Trench excavation works under bentonite slurry BGA Touring lectures 2010 .PORT OF BRISBANE – PADDOCK S3B Backfilling works Two membrane rolls . PORT OF BRISBANE – PADDOCK S3B BGA Touring lectures 2010 . PORT OF BRISBANE – PADDOCK S3B BGA Touring lectures 2010 . Ko = 1 Isotropic σ’1= 80kPa σ’2 = 80kPa σ’3 = 80kPa Kf (failure line) εh < 0 Ko (εh = 0) Passive Zone εh > 0 Vacuum Consolidation Mean Stress (p’) BGA Touring lectures 2010 .Stress path for Vacuum Process Vacuum Surcharge p’ = 2/3 σ’1 Ko = 0.5 Deviatoric Stress Stress (q’) (q) Deviation σ’1= 80kPa σ’2 = 40kPa σ’3 = 40kPa Active Zone Surcharge p’ = σ’1 . 1998 BGA Touring lectures 2010 .Case history : Kimhae (Korea) . Soil Improvement Techniques Without added materials Cohesive soil Peat . clay … 1 Drainage 2 VAcuum With added materials 4 Dynamic replacement 5 Stone columns 6 CMC 7 Jet Grouting 8 Cement Mixing Soil with friction Sand . fill 3 Dynamic consolidation 4 Vibroflottation BGA Touring lectures 2010 . 9-1 (SILICA SAND) = 0.Age if fill saturated or not -PL -Selfbearing level -∅ -EP or EM -QC.C.Paramaters for Concept CONCEPT FILL SBCσ’z GWT 80 % 50 % σ’ z FILL Depth (m) t (about 10 years) 1 2 3 4 S (%) 50% (SBC) 30% (SBC) 90% (SBC) 80% (SBC) 60% (SBC) FILL Depth (m) FILL+UNIFORM LOAD SBCσ’z GWT FILL+ LOAD SBCσ’z GWT PARAMETERS .9-1 C(hydraulic) = 0.4-0.6 (SILICA SAND) S.C. (???) -Shear wave velocity -Seismic parameters -Grain size 2 4 6 8 1 0 1 2 FILL Depth (m) 30% SB σ’z DC : h(m) = C δ E C(menard) = 0.D. FR.B. = Self Bearing Coefficient S. = S(t) S( ∞ ) ¥ BGA Touring lectures 2010 .B.55 δ δ SBC LOAD = 0. -N -R. Case History Nice airport runway consolidation Granular soil Very high energy (250 t . 40 m) BGA Touring lectures 2010 . KAUST PROJECT Concept and application of ground improvement for a 2.600.000 m² BGA Touring lectures 2010 . Typical Master Plan BGA Touring lectures 2010 . Discovering the Habitants BGA Touring lectures 2010 . Areas to be treated AREAS TO BE TREATED •AL KHODARI (1.800.000 m2) •BIN LADIN (720.000 m2) SCHEDULE • 8 month BGA Touring lectures 2010 Dynamic Consolidation Shock waves during dynamic consolidation – upper part of figure after R.D. Woods (1968). BGA Touring lectures 2010 Specifications •Isolated footings up to 150 tons •Bearing capacity 200 kPa •Maximum footing settlement 25 mm •Maximum differential settlement 1/500 •Footing location unknown at works stage BGA Touring lectures 2010 Engineered fill + 4.0 σz = 200 kn/m² 2 meters arching layer + 2.5 Working platform (gravelly sand) + 1.2 Compressible layer from loose sand to very soft sabkah 0 to 9 meters BGA Touring lectures 2010 .Concept 150 TONS Depth of footing = 0.8m Below G.L. 64 The equation has been revised recently by Varaksin and Racinais (2009) as: f −f f (z ) = 2 2 1 (z − NGL)2 + f1 D Where: f(z) is the improvement ratio at elevation (z).9 for metastable soils.6 for sands. young fills. Table Values of coefficient C in the equation Drop method Free drop Rig drop Mechanical winch Hydraulic winch Double hydraulic winch 0.75 0. Its value is given in Table.008E and E is the energy in tons-meter/m2. f1 is the maximum improvement ratio observed at ground surface and it is dimensionless. D is the depth of influence of dynamic consolidation.5 C 1.(D) = C δ WH where: C is the type of drop. z is the depth in meters. NGL is the natural ground level. δ is a correction factor. BGA Touring lectures 2010 . or very recent hydraulic fills and δ = 0. The value may be taken as f1 = 0.89 0.0 0.4 – 0. and f2 is the improvement ratio at the maximum depth of influence that can be achieved. δ = 0. 80 Preloading FPL DR (Dynamic Replacement) HDR (High Energy Dynamic Replacement) + surcharge Design > 2.50 BSL (variable) BGA Touring lectures 2010 .Selection of technique 0.80 WPL Working Platform NGL GWT Soil Conditions > 4. 9 2.5-1.8 PL BARS EP BARS 1 .SABKAH 2 .2-4 0.LOOSE SILTY SAND 3 .2 0.CORAL 4 .1-7.LOOSE TO MED DENSE SAND 0-2 12-45 15-80 0.4-1.Specifications ELEVATION (meters) +5 +4 +3 +2 +1 0 -1 -2 -3 -4 -5 -6 -7 -8 -9 -10 TYPICAL SITE CROSS SECTION OF UPPER DEPOSITS SITE ≅ 1.5-1.5 km LAGOON FILLED BY SABKAH +3 RED SEA e CORAL BARRIER c c 2 4 LAYER USC SM + ML SM SM w % 35-48 26-35 % fines 28-56 15-28 12-37 N 0-2 3-9 6-12 3-18 Qc BARS e 4 FR % 1.1-4 5.2 4-12 avr-17 18-35 35-60 28-85 BGA Touring lectures 2010 . Variation in soil profile over 30 meters BGA Touring lectures 2010 . Typical surface conditions BGA Touring lectures 2010 . BGA Touring lectures 2010 . – Saudi Arabia 1.I : energy specific improvement factor PLF PLi I × 100 E 40% LEGEND Average pre-treatment values Average values between phases Average post-treatment values 50% 0 0 100 200 300 400 Energy (kJ/m3) BGA Touring lectures 2010 .4 1.7 BASIS •60 grainsize tests •180 PMT tests PARAMETERS 20% 1 0.2 PL-Po (MPa) 10% I=8 SI = 4.5 I = 3.72 I=3 SI = 0.Analysis of improvement ANALYSIS OF (PL-Po) IMPROVEMENT AS FUNCTION OF ENERGY AND FINES K.6 1.6 0.3 KAUST KAUST 30% I = 5.2 DC DOMAIN DR DOMAIN •S.A.25 SI = 2.8 I = 6.U.4 0.56 500 •PL – Po = pressuremeter limit pressure •kJ/m3 = Energy per m3 (E) •% = % passing n°200 sieve •I = improvement factor 0.S.1 SI = 0.T.5 SI = 1. 602 0.037 0.632 0.848 if du=U1Δσ. then t’f = U1t1 + (1-U1)tf The optimal effectiveness occurs around U1 = 60%.807 0.00 Supposing primary consolidation completed U = 0.725 0.735 1.00 ⎤ ⎡ du C' V = C V ⎢1 + ⎥ ⎥ ⎢ Δσ(1 − U1) ⎦ ⎣ The following equation allows to compare the respective times of consolidation being : t’f with impact tf without impact t’1/tf 0. theoretically du + Δσ(1− U1 ) du + Δσ(1− U1 ) the consolidation time is reduced by 20% to 50%.669 1.148 0.9 or T = 0.083 0.474 0. where For the considered case. du = UΔσ and thus t’f = U1t1 + (1-U1)tf TV = 0.It can be assumed that those impacts du generate a pore pressure at least equal to the pore pressure generated by the embankement load. Δσ(1− U1 ) du t' f = t1 + tf One can thus conclude that. BGA Touring lectures 2010 .901 0. what is for practical purpose insufficient.848 = With C'v (t'1 −t1 ) Cv T1 + H² H² The Table allows to compare the gain in consolidation time.231 0.337 0.009 0.659 0. U 1 10% 20% 30% 40% 50% 60% 70% 80% 90% t1/tf 0. at different degrees of consolidation. This new consolidation process with the final at a time t’f.615 0. Dynamic surcharge BGA Touring lectures 2010 . BGA Touring lectures 2010 . VIBROFLOTS Amplitude 28 – 48mm BGA Touring lectures 2010 . PORT BOTANY EXPANSION PROJECT GROUND COMPACTION WORKS PORT BOTANY EXPANSION PROJECT GROUND COMPACTION WORKS EXTENSION PORT EXISTING PORT BGA Touring lectures 2010 60 . PORT BOTANY EXPANSION PROJECT GROUND COMPACTION WORKS EARLY WORKS 600 M NEW TERMINAL AREA TRENCH FOUNDATIONS / COUNTERFOURT BACKFILL 1300 M BGA Touring lectures 2010 . PORT BOTANY EXPANSION PROJECT GENERAL ARRAGEMENT COUNTERFORTS INCLUDING RECLAMATION BGA Touring lectures 2010 . 250.000.000 800.000 64.000 650.000 1.PORT BOTANY EXPANSION PROJECT RESUME / QUANTITIES PHASE AREA (M2) VOLUME (M3) TECHNIQUE EARLY WORKS TRENCH FOUNDATIONS 90.000 ONSHORE TANDEM VIBRO COMPACTION DYNAMIC COMPACTION NEW TERMINAL AREA 404.330.000 5.000 DC / VC BGA Touring lectures 2010 .000 TOTAL 650.000 DYNAMIC COMPACTION / VIBRO COMPACTION OFFSHORE VIBROCOMPACTION COUNTERFOURT BACKFILL 92.000 8. 0M GRID / 3 PHASES – 10 BLOWS BGA Touring lectures 2010 .0M X 5.PORT BOTANY EXPANSION PROJECT DYNAMIC COMPACTION POUNDER WEIGHT 25 TON / 23 METERS HIGH DROP 5. PORT BOTANY EXPANSION PROJECT LOAD OUT WHARF – VIBRO COMPACTION V48 UPLIFT STEPS 1.0M / 40 SEC EACH V48 REQUIRES WATER & AIR FOR COMPACTION BGA Touring lectures 2010 . PORT BOTANY EXPANSION PROJECT VIEW OF LOAD OUT WHARF – DC / VC WORKING BGA Touring lectures 2010 . PORT BOTANY EXPANSION PROJECT BGA Touring lectures 2010 . PORT BOTANY EXPANSION PROJECT BGA Touring lectures 2010 . Except for the upper 50cm.PORT BOTANY EXPANSION PROJECT RESULTS 1. the combination of VC and DC satisfied the qc = 15 MPa (upper 0. 2. Enforced settlement: After VC – 47cm After DC – 27cm Total – 74 cm (~ 10% of treatment depth) Compaction was less effective in this layer! stiff clay BGA Touring lectures 2010 .5m requires surface roller compaction). fill 3 Dynamic consolidation 4 Vibroflottation BGA Touring lectures 2010 .Soil Improvement Techniques Without added materials Cohesive soil Peat . clay … 1 Drainage 2 VAcuum With added materials 4 Dynamic replacement 5 Stone columns 6 CMC 7 Jet Grouting 8 Cement Mixing Granular soil Sand . Ey of soil. grid -or PL. ∅. column and arching layers. EP. µ of soil. μ. column and arching layers. grid BGA Touring lectures 2010 .Dynamic Replacement CONCEPT -Very soft to stiff soils -Unsaturated soft clays -Thickness of less than 6 meters -Arching layer available PARAMETERS -C. Stone Columns – Bottom Feed Vibrator penetration Material feeding Principle of the technology .bottom feed with air tank BGA Touring lectures 2010 Vibration of material during extraction . Stone Columns – Bottom Feed Stone Columns bottom feed to 22 m depth BGA Touring lectures 2010 . Stone Columns CONCEPT -Soft to stiff clays -Thickness up to 25 meters -Arching layer available PARAMETERS -C. grid -or PL. grid BGA Touring lectures 2010 . Ey of soil. column and arching layers. µ of soil. μ. column and arching layers. EP. ∅. CMC – Execution Fleet of specilized equipment Displacement auger => quasi no spoil High torque and pull down Fully integrated grout flow control Grout flow Soft soil BGA Touring lectures 2010 . Compression tests on material Checking of good grout resistance Data recording system during execution Recording of drilling parameters => Checking of anchorage. Recording of grouting parameters => No necking BGA Touring lectures 2010 .CMC – Typical Testing Load testing on isolated CMC Checking of individual capacity. Checking of adequate soil parameters taken into account. μ. γ. Ey.PARAMETERS SOIL -C’. ϕ -Kv. D (non porous medium) BGA Touring lectures 2010 . ∅’.RIGID INCLUSIONS . γ. Kh if consolidation is considered INCLUSION -Ey. μ. CMC Principle Create a composite material Soil + Rigid Inclusion (CMC) with: Increased bearing capacity Increased elastic modulus Transfer the load from structure to CMC network with a transition layer Transition layer Stress concentration CMC BGA Touring lectures 2010 CMC Residual stress Arch effect between the columns . Basic behavior under uniform load Negative skin friction allows to develop a good arching effect Settlement Negative skin friction Soil Positive skin friction Column Neutral point Stress in the column Depth BGA Touring lectures 2010 .CMC . CMC Design . Stiffness Global axisymetric calculation by modelising the improved ground by material having an improved stiffness Complex Soil + CMC with improved characteristics BGA Touring lectures 2010 .Principle Axisymetric FEM calculation with one CMC and the soil => eq. 3/ Thus maximum shear force taken by the includion (similar to a pile to which a displacement is applied). 2/ Thus maximum momentum so that M / N ≤ D / 8 (no traction in the mortar).CMC Design – Specific case of non vertical loading Calculation principle 1/ Estimation of the vertical stress in the column (% of the embankment load). R i δ Ti BGA Touring lectures 2010 . 4/ Modeling of the CMC as nails working in compression + imposed shear force under TALREN software (or equivalent). Structure very simple to be built: footings and slab on grade.CMC Design – Benefits for the structure Structure shall be designed as if soil was of good quality Specialist contractor provides structural designer with bearing capacity. etc… No connection between foundation and structure Structure is less complex to be designed. no pile cap. thus no increase under seismic analysis. k. No stiff connection. thus benefit in terms of cost and speed of execution BGA Touring lectures 2010 . r c rp a BGA Touring lectures 2010 .New Developement .Principle Aim of CMC CompactionDensify granular material to decrease liquefaction potential Method of densification Injected mortar used to displace and compact the soil around the injection point Successive injection according to a regular grid induce a global compaction of the soil Mesh and diameter designed so as to achieve a given replacement ratio Elast ic Plast ic σc P Pf 0 ρf 2.CMC Compaction . New Developement .CMC Compaction .Design Principle: Execution and testing procedure Seismic parameters (seism PGA. Magnitude) => qc soil profile to be achieved (Seed and Idriss methodology) Estimation of Replacement ratio to achieve required qc Execution of Works and testing by CPT Additional grouting if necessary Execution of Compaction Grouting as per preanalysis (replacement ratio => mesh and diameter) Execution of CPT testing Until CPT results are satisfactory Results not OK Results OK Execution of additional Compaction Grouting in the problematic layers BGA Touring lectures 2010 . workability. Key points Quality of grout (grain size distribution. consistancy) Injection speed and successive phases Final Testing = CPT BGA Touring lectures 2010 .CMC Compaction .New Developement .Execution Same type of equipment as for CMC Soil displacement rig and Pump. New Developement .CMC Compaction – Fos LNG Terminal BGA Touring lectures 2010 . DCM : Deep Cement Mixing CONCEPT BGA Touring lectures 2010 . Future Caisson Stability Analysis BGA Touring lectures 2010 . As built conditions BGA Touring lectures 2010 . Proposed solution Layer I Layer II 15% rock (φ = 45°) + 85% clay (Cu = 50 kPa) BGA Touring lectures 2010 . View of pounder construction BGA Touring lectures 2010 . View of pounder ready to work BGA Touring lectures 2010 . General SFT up BGA Touring lectures 2010 . 3m Cu=50kPa Cu=50kPa Cu=250kPa BGA Touring lectures 2010 .4m 1.After compaction actual results Original rock surface before compaction 0.4m φ=40 degree φ=48 degree Ar=22% C=0kPa Column Dia=2.3m 1.2m φ=48 degree Ar=22% C=0kPa Column Dia=2.4m φ=40 degree φ=48 degree Ar=22% C=0kPa Column Dia=2. BGA – TOURING LECTURE – NOVEMBRE 2010 ISSMGE 95 .