Improvement of Cohesive Strength of Local Clay by Sandwich Method

Abstract

Improvement Of Cohesive Strength Of Local Clay By Sandwich Method paper presents a series of consolidated-undrained triaxial compression tests to investigate geotextile-reinforced clay’s shear behavior and generate excess pore water pressure during undrained loading. The experimental results revealed that non woven geotextile as a permeable material reduced the consolidation time during consolidation; however, it induced a higher volume change.

The shear strength and excess porewater pressure of the reinforced clay increased with the number of geotextile layers during undrained loading due to the restraint of the lateral deformation resulting from the mobilized tensile strength of reinforcement layers.

Both effective and total stress failure envelopes of the reinforced clay shifted upward as the number of reinforcement layers increased and appeared parallel to those of the unreinforced clay.

Results of numerical simulation using FLAC3D computer program, in which dynamic compaction is modeled as a three-dimensional, coupled hydro-mechanical model, are presented to highlight the mechanisms of positive pore pressure generation due to dynamic compaction. Both field studies and numerical simulation results support the mechanisms of HVDM in that dynamic compaction induced positive pore water pressure together with vacuum generated negative pore water pressure added effects in rapidly expelling water from the soil, thus increasing density (reduction of void ratio)

Conclusion

A case study presented the results of monitoring and evaluation of a pilot testing program at Ningbo Port Project in China. Site monitoring data confirmed the working principles of the method of ground improvement described.

Three-dimensional numerical simulations of HVDM using FLAC3D program indicated the positive generation of pore pressure in nearly saturated fine-grained soils due to dynamic compaction.