不同含水率花岗岩残积土-格栅界面剪切特性

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

摘要:

花岗岩残积土可作为回填土应用于加筋土结构，含水率对结构的稳定性具有重要影响。以广州市增城区花岗岩残积土为研究对象，通过室内大型直剪试验，研究了不同含水率（13%、19%、25%、32%）、竖向应力（50、100、150、200kPa）对花岗岩残积土-格栅界面剪切特性曲线、抗剪强度、体变特性的影响。试验结果表明：含水率为13%、竖向应力为50kPa时，残积土-格栅界面剪应力随着剪切位移的增大先升后降，降幅较小，其余条件下剪应力随着剪切位移的增大而升高；格栅加筋能够缓解花岗岩残积土剪应力达到峰值后大幅降低的剪切软化趋势；筋土界面抗剪强度随着含水率的升高而大幅降低，界面抗剪强度系数整体上随着含水率的升高先增加后降低，含水率为19%和25%时格栅加筋的增强效果最佳；筋土界面黏聚力随着含水率的增加先增大后减小，界面内摩擦角随着含水率的升高而降低；13%、19%含水率下筋土界面在50kPa竖向应力作用下发生了剪胀，其余条件下体积应变以剪缩为主。

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.