TOPIC 4SOIL COMPACTION SOIL COMPACTION – History and Evolution SOIL COMPACTION – History and Evolution SOIL COMPACTION Why and when is needed . SOIL COMPACTION Why and when is needed Changes in soil as it moves from its natural location to a compacted fill . Highway construction – cut and fill work Site proposal . Oroville Dam – California (Earth dam) . Sanitary Landfill . Sanitary Landfill . Cut Slope – using compacted soil (Faculty of Economy UM – new wing . Cut slope – using key stone at the toe (Fakulty of Economy UM – New wing . Pahang) .Natural soil Backfill material Retaining Wall (Lembah Bertam. applying static weight and impact.What is COMPACTION Definition Process of increasing the density of soil by packing the particles closer together causing reduction in the volume of air via mechanical techniques such as rolling. air Dry density ↑ water Ms ρd = V solid BEFORE AFTER . without significant change in the volume of water. kneading. Objective To improve engineering properties of soil through Increasing the shear strength. shear strength is at maximum when void ratio is minimum Reducing the compressibility of soil – settlement Reducing permeability Reducing the potential of swelling (expansion) and shrinkage (contraction) due to frost action. . compactive effort.Degree of Compaction How compact the soil is. soil type and compaction method. . in other words the condition of soil after compaction is termed as DEGREE OF COMPACTION Measured in terms of DRY DENSITY Ms ρd = V ρd = ρ 1+ w The dry density depends on water content. Compaction Test Standard Proctor Test– BS 1377 (a) Cylindrical Mould . volume = 1000 cm3 (b) Hammer 2.5 / 4.5 kg . (i) Stop the process when the weight of the compacted soil start to decrease (j) Draw compaction curve – dry density vs water content .Test Procedure (a) Take 3 kg of soil (passed 20 mm sieve) and break up any lumps (b) Assemble and weigh the mould (base + mould body) (c) Add 3% water (% by weight) and mix (d) Fix the extension and put soil in three layers. (h) Repeat steps (c) – (g) with each repetition. each layers receiving 27 blows of rammer. increasing the volume of water at 3% each time. break them up and take small amount for water content test. (e) Remove the extension and level off the excess (f) Weigh the compacted soil and the mould (g) Take out the soil from the mould. 49 kg 305 mm 944 cm3 3 25 Modified AASHTO ASTM D1557-78 AASHTO T180 4. of blows 2.5 kg 300 mm 1000 cm3 3 27 4.Types of compaction tests Test Refs.5 kg 450 mm 1000 cm3 5 27 Std Proctor AASHTO ASTM D698-78 AASHTO T99 2.5 kg rammer BS 1377 : 1975 Test 13 4.5 kg rammer BS 1377 : 1975 Test 12 2. Rammer Mass Height of drop Volume of mould Layer No.54 kg 457 mm 944 cm3 5 25 . Compaction Test Results Principles of compaction . Compaction Test Results Relationship between dry density and water content -Typical compaction curve -Each compaction curve is unique (one curve for a particular compactive effort or compactive method) For each curve there is an optimum water content (wopt) that contribute to the maximum dry density (ρdmax) . facilitating compaction hence resulting in higher dry density. the water content is adequate for adsorbed water to develop. therefore. Water is adequate to produce workable soil. Most compactive effort is used to break up lumps . This excess pressure results in soil particles expels and pushes each other. forces between particles are reduced allowing dispersed orientation to formed. increasing spaces (voids). For clayey soil. Difficult to compact. hence decreasing the dry density.Properties of Compaction Curve Compactive effort is taken up by water in the pore which is already full as excess pore water pressure. Soil rather stiff and lumpy. Saturation Line If all air in soil could be expelled by compaction (A=0) (impossible in reality), then the soil will be in full saturation. The max. dry density at this condition is called Saturation dry density / ‘zero air voids’ dry density Gs ρ w ρd = 1 + wGs Gs (1 − A) ρ w ρd = 1 + wG s Example Problem 1.5 – Craig pg 33 Soil has been compacted in an embankment at a bulk density of 2.15 Mg/m3 and water content of 12%. The value of Gs is 2.65. Calculate the dry density, void ratio, degree of saturation and air content. Would it be possible to compact the above soil at water content of 13.5% to a dry density of 2.00 Mg/m3 Example Problem 6.22 – Coduto page 205 A well graded silty sand with a maximum dry unit weight of 19.7 kN/m3 and optimum moisture content of 11% is being used to build a compacted fill. Two field density tests have been taken in the recently completed field, but one of these tests has produced results that are definitely incorrect. Test A indicated a relative compaction of 85% and a moisture content of 8.9%, while Test B indicated a relative compaction of 98% and a moisture content of 14.9%. Which test is definitely incorrect? Why? Assume Gs as 2.70. dry density occur for a particular soils Test curve must be at the left of saturation line ρd = Gs (1 − A) ρ w 1 + wG s .Air Content Line If A is replaced by 5% and 10% curves for air content of 5% and 10 % can be drawn hence can be used to indicate at what percentage of air content max. Factors affecting compaction Compactive Effort The higher the compactive effort – the higher the degree of compaction Compaction curve shift to the left and upward when there is an increase Compaction energy per unit volume (E) = (no of blows per layer x no of layers x weight of rammer x drop height) / vol. of mould . Well graded soil? .Factors affecting compaction Soil Type For the same compactive effort Coarse-grained soil can be compacted to a higher degree of compaction. .Factors affecting compaction Soil Type Granular material with some fines will exhibits higher degree of compaction compared to granular material without fines or finegrained soil alone. Factors affecting compaction Compaction method Rolling – granular soil? Impact – granular / fine? Kneading – fine-grained? Vibration – granular? Static load – fine/ coarse-grained? . 30 wL 70 (a) Type A 1½ peak type For soil where wL < 70 100% or high % of sand and remaining is either illite / montmorillonite Typical for non-cohesive soil (b) Type B .Compaction Curves Single peak type Common shape . Lengkung Pemadatan 2 peaks type For soil wL < 30 Portion of soil is sand and some kaolinite (c) Type C No peak Fines where wL > 70 Main portion is montmorillonite Some linear part of the curve presence (d) Type D . there exits 2 corresponding values of w (one at the dry and another at the wet side).Dry and Wet side of Optimum ρd DRY WET w1 w2 AT OPTIMUM At any particular ρd value. apart from ρdmax. Which value is to be used in engineering work? . Effect of compaction on the dry and wet side Part of water content dry wet strength high low Compressibility (at low consolidation pressure) (at high consolidation pressurei) low High high low Swelling High low low high Engineering properties Shrinkage . 1959). hence reducing repulsion. Clay particle and hence reducing degree of flocculation . Clay ptcl. Increase in water content (B-C) increases repulsion bet. Due to less water for diffused double layers of ions to developed around ptcls. results in dispersed structure. diffuse double layer expand and this increase repulsion bet. when water content increase. Increase dispersion as compactive effort increases At B. the structure is flocculated irrespective of compactive effort (Seed and Chan.Structure of Compacted Clay Soil On the dry side. if the soil is wet. On the other hand. they need to be dried up to the required water content. the soil need to be wet prior to compaction according to the water content required for certain degree of compaction. Fill materials that has been excavated will be brought to the construction area and levelled in several layers of (150 mm – 500 mm thickness) depending on the types of soil and equipment used. .Field Compaction Fill material that has been excavated from a borrow site need to be compacted. If the soil to be compacted is naturally dry. Field Compaction .Equipment Excavators / Rippers – Excavate soil Wheel-mounted loader Backhoe + loader Excavator (large hoe) . Field Compaction .Equipment End Dump Truck . Field Compaction .Equipment Spreader . of passes or coverages Type of equipment – type of soil and site condition / fill .Field Compaction Equipment Equipment – Vibrating plates. kneading action. vibration or impact. power rammers and many different types of rollers Methods – combination of static pressure. Compactive effort – no. g.Field Compaction Equipment Vibrating Plates / Power Rammers Usage – small areas with limited access e. bridge abutment. narrow trenches. road subbase Compaction method – vibration and static weight CAUTION ! – normally hand operated and selfpropelled . pavement. May be used for fine material provided not too wet and not to be used for compaction of impermeable core section of eater retaining structure due to smooth interface being introduced Compaction method – static weight ~ 400 kN/m2 Can be self-propelled or towed .Field Compaction Equipment Smooth-wheeled Rollers Usage – subgrade or base course compaction of wellgraded sand/gravel mixtures or asphalt pavements. Compaction method – static pressure and kneading May be self-propelled or towed Tapered protrusion ‘feet’ exerting contact pressure 1500 – 7500 kN/m2 . particularly applicable in earth dam construction where bonding between lifts of impermeable core are ensured.Field Compaction Equipment Sheepsfoot rollers Usage – for fine-grained soil ( >20% fines). Field Compaction Equipment Rubber-tyred rollers Usage –for fine and coarse-grained soil except uniformly graded Compaction method – static pressure up to 700kN/m2 and kneading . Field Compaction Equipment Vibratory Rollers Usage – For granular soil without fines Vibrators are attached to smooth rollers Compaction methods – vibration ranges 20 – 80 Hz . Field Compaction Equipment . Application of Field Compaction Equipment . Specification and Control of Field Compaction The extent to which field compaction is effective depends on Types of soil Water content Lift thickness Type of compaction equipment The size of fill area No. of passes / coverages Why specification is required? –to ensure compaction is carried out adequately on-site . Hence. compaction may be achieved via two w (dry / wet side).Compaction Specification SPECIFICATION End Result To be Achieved Method of Compaction Prescribe a required Relative Compaction and w Engineer prescribe weight and type of rollers. compactive effort etc. specify w as well (range). . number of coverages. lifts thickness RC =(ρdfield/ρdmax)x 100% RC of normally between (90100%). specify final air voids content with associated max. Alternatively. water content Combination of the three factors can be determine from several trial exercises on actual sites using different equipments. lifts thickness. Compaction Specification SPECIFICATION End Result To be Achieved Method of Compaction Which one do you choose? CONSULTANT CONTRACTOR Why? . Control of Field Compaction The need… . Control of Field Compaction Objective – to ensure work meets specification for compaction Technique – Need to find ρ (from M and V) put them back in ρd (need also w) CONTROL TEST Coarse-grained soil Fine-grained Soil cylindrical core-cutter BS1377:1975. Test 15(D) Determine mass and volume Determine w Test hole BS 1377:1975. Test 15(A) – (C) Determine mass and volume Determine w Nuclear Method . Cylinder having known volume V Weigh the cutter before and after soil extraction to get M Moisture content test to get w .Control of Field Compaction Fine-grained Soil (Cylindrical core cutter) Push the core cutter until full.let some sample to dry for 24 hr in the oven ρ ρ M V = d = . ρ (1 + w ) . dug out and trimmed flush the end. Control of Field Compaction Coarse-grained Soil – Test Hole Excavate a hole at the desired level in the soil Place the excavated soil into a container and weight for M Take some sample for moisture content test . w Determine the volume V from either Volume of Hole (V) Sand Replacement Method Rubber Balloon Method BS 1377 : 1975 Test 15(A) ASTM D-2167-66 . . From the mass of sand being filled up. V can be calculated Problem – vibration from surrounding operation might introduced errors.Control of Field Compaction Sand Replacement Method Determine V by filling the excavated hole with sand of known bulk density. Control of Field Compaction Rubber Balloon Method Determine V by filling the rubber balloon with water so that it stretches across the hole Problem – error is introduced when the sides of the hole is too rough . Control of Field Compaction Water Ring Test . Control of Field Compaction Problems with traditional methods M – OK ? Errors? V.OK? Errors? w – require 24 hours / use ‘speedy moisture tester’ The ease of repetitive of test over the whole construction area To overcome – consider using the Nuclear Method . hence allowing corrective action to be taken.Control of Field Compaction Nuclear Method Objective – to determine ρ and w Basic Principle 2 emission sources and 2 detectors γ ray Neutron ρ (γ ray scattered as they collided with soil particles) w (energy ↓ when neutron collided with hydrogen atom Results can be achieved in minutes. Many repetitive test can be carried out over the whole field – good control practice . Fine-grained soil Insert probe into the soil and place the detector onto the soil surface. Back-scatter – Coarse-grained soil A single unit is placed on the surface of the soil and the same work as both emission source and detector .Control of Field Compaction Nuclear Test Equipment – ASTM D-2922-78 Direct Transmission . Control of Field Compaction Nuclear density and water content determination transmission (after Troxler Electronic Laboratories.. North Carolina) (a) Direct transmission (a) backscatter (c) Air-gap . Research Triangle Park. and compacting it using a towed sheepfoot roller. The measured moisture contents ranged from 10 to 23%. spraying the top with a water truck. The specifications require a relative compaction of at least 90%. so the fill is not acceptable.19 – Coduto page 204 A fill soil with a natural a moisture content of 10% and an optimum moisture content of 14% is being used to construct a compacted fill. What is wrong with the contractor’s methods.Example Problem 6. A soil technician has performed a series of field density tests in this fill and has found relative compaction values between 80% and 92%. and what needs to be done to remedy the problem . The contractor is placing this soil in 400mm lifts. Compaction in engineering industry Review on Menard Geosystem Presentation – CEEC Technical talk on Sept. 05 .