GROUND IMPROVEMENT PRINCIPLES OF COMPACTION

A good foundation has a safe and economic design with the following properties: 1.Have adequate shearing strength and bearing capacity. 2.Have minimum deformation and consolidation load. 3.Have minimum volume change from swelling, shrinkage, or dynamic loading. 4.Retain strength and resist deformation with time. 5.Favorable water table, permeability, etc. with respect to the project.

ENGINEER CHOOSE ANY OF THE FOLLOWING: 1.Adapt with the conditions by using deep foundation (pile etc) or shallow foundation (wide raft etc) 2.Improve the ground properties by increasing strength, reducing permeability, reducing compressibility 3.Abandon the site

Altering soil properties of a site is called soil stabilization with methods such as: I.Densification by Compaction, Pre-compression, Drainage, Vibration, and Combination of methods II.Mixing or impregnation of the soil formation with Chemicals, Grouting, and Geofabrics III.Replacement of undesirable soil with suitable one

Compaction: Of the number of improvement methods, compaction is usually the 1.Least expensive, and 2.the most widely used method. It is used frequently to 1.Increase the density in-situ soil, and 2.Used as the universal method for engineered fill

Benefits from compaction includes: 1.Increase soil strength ( γ, ø, c ) and hence bearing capacity 2.Reduction in void, settlement, and permeability 3.Reduced shrinkage. The increased soil strength and improved bearing capacity is attained by the increase in the value of c,ø,γ. Reduction in void ratio may be achieved by particle re-orientation subsequent to 1.Alteration of the soil structure 2.Crushing and changes in the geometry of the soil grains. 3.Distortion of grains The reduced shrinkage benefits come as a result of a higher resistance to deformation and a smaller void ratio. Consolidation and shrinkage are due to reduction in void ratio.

FIELD DENSITY TEST

FIELD DENSITY TEST - A small hole (6" x 6" deep) is dug in the compacted material to be tested. The soil is removed and weighed, then dried and weighed again to determine its moisture content. A soil's moisture is figured as a percentage. The specific volume of the hole is determined by filling it with calibrated dry sand from a jar and cone device. The dry weight of the soil removed is divided by the volume of sand needed to fill the hole. This gives us the density of the compacted soil in lbs per cubic foot. This density is compared to the maximum Proctor density obtained earlier, which gives us the relative density of the soil that was just compacted.

1. Void Ratio 2. Porosity 3. Degree of Saturation 4. Water Content 5. Moisture Content 6. Unit Weight 7. Bulk Unit Weight 8. Dry Unit Weight 9. Effective Unit Weight 10. Density 11. Dry Density 12. Saturated Density 13. Specific Gravity of Solid VvVv VwVw VsVs WwWw WsWs Exercise – Assignment 1 – Derive the definitions based on the phase diagram

1. Void Ratio 2. Porosity 3. Degree of Saturation 4. Water Content 5. Moisture Content 6. Unit Weight 7. Bulk Unit Weight 8. Dry Unit Weight 9. Effective Unit Weight 10. Density 11. Dry Density 12. Saturated Density 13. Specific Gravity of Solid (Assume 2.65) Exercise – Assignment 2 – Derive the definitions based on the phase diagram 0.5 m 3 1 m 3 VsVs MWMW 3000 kg