Shear Characteristics of Granite Residual Geogrid-Soil Interface with Different Water Contents

Abstract:

Granite residual soil can be used as backfill in reinforced soil structure， and its water content has an important effect on its mechanical properties. Taking the granite residual soil in Zengcheng District， Guangzhou as the research subject， large-scale direct tests are conducted to analyze the shear characteristics， shear strength， and volume deformation properties of the residual soil and its interface with different water contents （13%， 19%， 25%， and 32%） and normal stresses （50， 100， 150， and 200kPa）. The test results show that when the water content is 13% and the vertical stress is 50kPa， the shear stress of residual soil-geogrid interface increases first and then decreases with the increase of shear displacement， and the shear stress increases with the increase of shear displacement in other conditions. The geogrid reinforcement can alleviate the shear softening of granite residual soil which decreases greatly after the shear stress reaches the peak value. The interface shear strength decreases greatly with the increase of water content， and the interface shear strength coefficient increases first and then decreases with the increase of water content. When the water content is 19% and 25%， the reinforcement effect is the best. The interface cohesion increases first and then decreases with the increase of water content， and the interface friction angle decreases with the increase of water content. At a water content of 13% and 19%， the soil-reinforced interface dilates at a vertical stress of 50kPa， and the bulk strain is mainly shear shrinkage under other conditions.