1 Compaction N. Sivakugan Duration = 10 minutes

SIVA Copyright© What is compaction? A simple ground improvement technique, where the soil is densified through external compactive effort. + water = Compactive effort

SIVA Copyright© Compaction Curve Water content Dry density (  d ) optimum water content  d, max Soil grains densely packed - good strength and stiffness - low permeability

SIVA Copyright© Compaction Curve What happens to the relative quantities of the three phases with addition of water? Water content Dry density (  d ) soil water air difficult to expel all air lowest void ratio and highest dry density at optimum w

SIVA Copyright© Zero Air Void Curve All compaction points should lie to the left of ZAV curve - corresponds to 100% saturation Water content Dry density (  d ) Zero air void curve (S=100%) S<100% S>100% (impossible)

SIVA Copyright© Effect of Compactive Effort Increasing compactive effort results in: E1E1 E 2 (>E 1 )  Lower optimum water content  Higher maximum dry density  Lower optimum water content  Higher maximum dry density Water content Dry density (  d )

SIVA Copyright© Compaction and Clay Fabric Higher water content or higher compactive effort gives more dispersed fabric. more dispersed fabric Water content Dry density (  d )

SIVA Copyright© Line of Optimum Water content Dry density (  d ) Compaction curves for different efforts Line of optimum

SIVA Copyright©2001 Filed Compaction  Pneumatic rubber tired roller Different types of rollers (clockwise from right):  Vibratory roller  Smooth-wheel roller  Sheepsfoot roller

SIVA Copyright© Field Compaction Compacts effectively only to mm; therefore, place the soil in shallow layers (lifts) Smooth Wheeled Roller

SIVA Copyright© Field Compaction  for compacting very small areas Vibrating Plates  effective for granular soils

SIVA Copyright© Field Compaction  Provides kneading action; “walks out” after compaction Sheepsfoot Roller  Very effective on clays

SIVA Copyright© Field Compaction  Provides deeper (2-3m) compaction. e.g., air field Impact Roller

SIVA Copyright© Compaction Control -a systematic exercise where you check at regular intervals whether the compaction was done to specifications. e.g., 1 test per 1000 m 3 of compacted soil Minimum dry density Range of water content Field measurements (of  d ) obtained using sand cone nuclear density meter

SIVA Copyright© Laboratory Compaction Test - to obtain the compaction curve and define the optimum water content and maximum dry density for a specific compactive effort. hammer Standard Proctor: Modified Proctor: 3 layers 25 blows per layer 5 layers 25 blows per layer 2.7 kg hammer 300 mm drop 4.9 kg hammer 450 mm drop 1000 ml compaction mould

SIVA Copyright© Compaction Control Test compacted ground  d,field = ? w field = ? Compaction specifications Compare! w dd

SIVA Copyright©2001 Dynamic Compaction - pounding the ground by a heavy weight Suitable for granular soils, land fills and karst terrain with sink holes. Crater created by the impact Pounder (Tamper) solution cavities in limestone (to be backfilled)

SIVA Copyright©2001 Dynamic Compaction Pounder (Tamper) Mass = 5-30 tonne Drop = m

SIVA Copyright©2001 Dynamic Compaction

SIVA Copyright©2001 Vibroflotation Vibroflot (vibrating unit) Length = 2 – 3 m Diameter = 0.3 – 0.5 m Mass = 2 tonnes Practiced in several forms:  vibro–compaction  stone columns  vibro-replacement Suitable for granular soils (lowered into the ground and vibrated)

SIVA Copyright©2001 Vibroflotation

SIVA Copyright©2001 Vibroflotation

SIVA Copyright©2001 Vibroflotation

SIVA Copyright©2001 Vibroflotation

SIVA Copyright©2001 Vibroflotation

SIVA Copyright©2001 Vibroflotation

SIVA Copyright© Stone Columns vibrator makes a hole in the weak ground hole backfilled..and compacted Densely compacted stone column

SIVA Copyright© Blasting Aftermath of blasting Fireworks? For densifying granular soils

SIVA Copyright© Earthmoving Equipment Large Excavator (see minivan on left for scale) David and Goliath?

SIVA Copyright© Earthmoving Equipment Grader for spreading soil

SIVA Copyright© Earthmoving Equipment Bulldozer for spreading soil evenly

SIVA Copyright© Earthmoving Equipment Loader

SIVA Copyright© Earthmoving Equipment Backhoe

SIVA Copyright© Earthmoving Equipment Crawler mounted Hydraulic Excavator

SIVA Copyright© Earthmoving Equipment Rock Breaker