New M.Tech. Thesis Submitted from Civil

IMPROVEMENT IN STRENGTH OF SILTY SOIL BY MIXING POLYPROPYLENE FIBER AND STONE DUST by Jagjeevan Singh

Abstract

Soil is the unconsolidated part of earth crust or rock and which is produced by physical or chemical disintegration of the various rocks. Construction of geotechnical structures on weak soil is highly risky because such soil is more susceptible to differential settlements due to their poor strength and high compressibility. Accumulation of solid waste is another serious problem faced by the world for which huge area of land is required for its disposal. Among the recent development, introduction of reinforcement in different form and use of the solid waste is being tried to improve the overall soil behavior. The objective of this study is to increase strength of silty soil using polypropylene fiber and Stone Dust. Different proportions of stone dust used were as 10, 20, 30 and 40% and polypropylene fiber were as 0.5, 1 and 1.5% to dry weight of soil.In this study, series of laboratory tests such as compaction test, California bearing ratio test and direct shear test were performed. From the compaction test it was observed that MDD increases and OMC decreases with increase in stone dust. Soaked CBR value of virgin soil was 2.92% and maximum percentage increase in CBR value was observed at 30% stone dust i.e. 6.08%. The stone dust was optimized at 30% and was used for further work. Further with increase in fiber content by keeping stone dust optimum MDD decreases and there was no significant change in OMC. On addition of Polypropylene fiber CBR value increased and maximum value was observed at 1% i.e. 8.02%. In direct shear test, cohesion value and angle of shearing resistance for virgin soil was 0.27 kg/cm2 and 210 respectively. With addition of stone dust cohesion value decreases and angle of internal friction increases. Further with addition of PP fiber cohesion value and angle of internal friction both increases. From the above results it was concluded that use of stone dust along with polypropylene fiber reinforcement proved to be effective method for stabilizing soil. The best proportion obtained was 69% Soil + 30% Stone Dust + 1% Polypropylene fiber.