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Ground Ground ImprovemeImproveme

ntntDr. Talat BaderDr. Talat Bader

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Dynamic CompactionDynamic Compaction

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Dynamic Deep Dynamic Deep CompactionCompaction

• Dynamic compaction was Dynamic compaction was first used in Germany in the first used in Germany in the mid-1930’s.mid-1930’s.

• Menard technique FranceMenard technique France

• Dynamic Deep Compaction is Dynamic Deep Compaction is simply the dropping of heavy simply the dropping of heavy weights on ground surface to weights on ground surface to densify soils at depthdensify soils at depth

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Why Dynamic Deep Why Dynamic Deep CompactionCompaction

•Reduce foundation Reduce foundation settlements settlements

•Reduce seismic subsidence Reduce seismic subsidence

•Permit construction on fills Permit construction on fills

•Densify garbage dumps Densify garbage dumps

•Improve mine spoils Improve mine spoils

•Induce settlements in Induce settlements in collapsible soils collapsible soils

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Important Construction Important Construction ConditionsConditions

• The Drop Weights ranges The Drop Weights ranges from 8 to 200 tonsfrom 8 to 200 tons

• Drop Heights ranges from 50 Drop Heights ranges from 50 to 100 ft.to 100 ft.

• Impact grids of 7 x 7 ft to Impact grids of 7 x 7 ft to 20 x 20 ft20 x 20 ft

• Minimum 100-150 ft Minimum 100-150 ft clearance from any structure clearance from any structure

• Review site for vibration Review site for vibration sensitivitysensitivity

• Primarily for silts and sands Primarily for silts and sands but also clays but also clays

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LimitationsLimitations

•Problems near Problems near groundwatergroundwater

•Multiple passes Multiple passes to compact at to compact at depthdepth

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Effect of Drop on Effect of Drop on the Groundthe Ground

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Important TermsImportant Terms

•Effective DepthEffective Depth -- Maximum depth of -- Maximum depth of ground improvement ground improvement

•Zone of Major DensificationZone of Major Densification -- About -- About upper 2/3 of effective depth upper 2/3 of effective depth

•Energy LevelEnergy Level -- Energy per blow -- Energy per blow (weight times drop height) (weight times drop height)

•Energy Intensity FactorEnergy Intensity Factor -- Involves -- Involves energy level, spacing, and number of energy level, spacing, and number of blows blows

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Depth of InfluenceDepth of Influence

From Holtz and Kovacs, 1981

whCD whCD

w = Weight of drop (Tons)

h = Height of drop (m)

D = Depth of influence (m)

C = Factor= .3-.7 Depends on soil type

w = Weight of drop (Tons)

h = Height of drop (m)

D = Depth of influence (m)

C = Factor= .3-.7 Depends on soil type

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Dynamic Dynamic compactioncompaction

D = 0 . 5 W H

D = W H

W i s w e i g h t a n d H i s h e i g h t o f d r o p

E n e r g y d r o p/

Depthof

Influence 8 0 J / m ½

3 0

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Dynamic Dynamic CompactionCompaction

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Important Geotechnical Important Geotechnical ParametersParameters

•Soil conditions Soil conditions

•Groundwater level Groundwater level

•Relative density Relative density

•Degree of Degree of saturation saturation

•Permeability Permeability

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Quality ControlQuality Control

•Crater depths (map) Crater depths (map) •Surface elevation Surface elevation

monitoring monitoring •Decrease in depth of Decrease in depth of

weight penetration with weight penetration with successive drops successive drops

•Pore pressures Pore pressures •Geophysical monitoring Geophysical monitoring

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Thank youThank you

Question TimeQuestion Time

Dr. Talat BaderDr. Talat Bader