Compaction N. Sivakugan Duration = 10 minutes

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

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

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

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

Effect of Compactive Effort Water content Dry density (d) Increasing compactive effort results in: E2 (>E1) Lower optimum water content Higher maximum dry density E1

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

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

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

Field Compaction Smooth Wheeled Roller Compacts effectively only to 200-300 mm; therefore, place the soil in shallow layers (lifts)

Field Compaction Vibrating Plates for compacting very small areas effective for granular soils

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

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

e.g., 1 test per 1000 m3 of compacted soil Compaction Control a systematic exercise where you check at regular intervals whether the compaction was done to specifications. e.g., 1 test per 1000 m3 of compacted soil Minimum dry density Range of water content Field measurements (of d) obtained using sand cone nuclear density meter

Laboratory Compaction Test to obtain the compaction curve and define the optimum water content and maximum dry density for a specific compactive effort. hammer Modified Proctor: Standard Proctor: 5 layers 25 blows per layer 3 layers 25 blows per layer 1000 ml compaction mould 4.89 kg hammer 450 mm drop 2.6 kg hammer 310 mm drop

Compaction Control Test w d Compaction specifications Compare! d,field = ? wfield = ? compacted ground

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

Dynamic Compaction Pounder (Tamper) Mass = 5-30 tonne Drop = 10-30 m

Dynamic Compaction

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

Vibroflotation

Vibroflotation

Vibroflotation

Vibroflotation

Vibroflotation

Vibroflotation

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

Blasting For densifying granular soils Aftermath of blasting Fireworks?

Earthmoving Equipment David and Goliath? This is an Australian excavator, with height of a 3-storey building Large Excavator (see minivan on left for scale)

Earthmoving Equipment Grader for spreading soil

Earthmoving Equipment Bulldozer for spreading soil evenly

Earthmoving Equipment Loader

Earthmoving Equipment Backhoe

Earthmoving Equipment Crawler mounted Hydraulic Excavator

Earthmoving Equipment Rock Breaker