SEMINAR ON

COMPACTIONBY

SUVADEEP DALAL

DEPARTMENT OF CIVIL ENGINEERING

IIT KHARAGPUR, KHARAGPUR

JANUARY 2012

What is Soil Compaction

Densification of soil by the application of mechanical energy.

Compaction Consolidation(i)Short term

process.(ii) Elastic

settlement occurs.

(iii) Reduction of air content at a given water content.

(iv) Soil is always unsaturated.

(i)Long term process

(ii) Plastic or permanent settlement occurs.

(iii) Expulsion of pore water from voids.

(iv) soil is completely saturated.

Method of Compaction

Cohessionless soils are compacted by dynamic method of compaction (vibration).

Cohessive soils are compacted by static compaction.

Objective of Compaction

Detrimental settlements can be reduced.

Soil strength and slope stability can be improved.

Bearing capacity of subgrade can be improved.

Undesirable volume change due to swelling , shrinkage may be controlled.

Factors Affecting Compaction

Water content Compacting effortMethod of compactionType of soilAddition of admixtures

Laboratory test

Proctor Test

Standard Proctor

Modified Proctor

Standard Proctor Test

Specification Description(i) Mass of hammer (i) 2.495 Kg(ii) Height of drop (ii) 304.88 mm(iii) Number of drops (iii) 25(iv) Number of layers (iv) 3(v) Volume of mould (v) 0.944*10^-3 m^3

Compactive effort = (2.495)*(9.81)*(304.88/1000)*(3)*(25)/(0.944*10^-3) = 592.7 KJ/m^3

Modified Proctor Test

Specification Description(i) Mass of hammer (i) 4.536 Kg(ii) Height of drop (ii) 457 mm(iii) Number of drops (iii) 25(iv) Number of layers (iv) 5(v) Volume of mould (v) 0.944*10^-3 m^3

Compactive effort = (4.536)*(9.81)*(457/1000)*(5)*(25)/(0.944*10^-3) = 2693 KJ/m^3

Procedure

Determination of Dry-density Moisture Content Relationship

Fig.1: Dry Density Vs Moisture Content Relationship

Effect of Compaction on Soil Properties

Structure of SoilPermeability ShrinkageSwellingPore Pressure CompressibilityShear Strength