不同环剪方式下滑带土残余强度试验研究

Study of residual strength of slide zone soil under different ring-shear tests

以三峡库区黄土坡滑坡滑带土为研究对象,利用环剪仪研究了黄土坡滑坡滑带土在单级剪、预剪以及多级剪3种环剪方式下的残余强度特征。试验结果表明:不同环剪试验下剪切带的形成与剪切位移相关;残余强度随有效法向应力的增大而增大,对于已经存在剪切带的滑带土,环剪时能很快达到残余强度状态;滑带土环剪轴向压缩分初始剪胀、颗粒运移压密和稳定压密3个阶段,且每个阶段剪应力变化趋势不同;预剪试验和多级剪切试验得到的残余强度偏大,应该首选单级剪切试验测试滑带土残余强度指标。

Slide zone soil of Huangtupo landslide is studied in detail as a typical example in the Three Gorges Reservoir.Three types of shear methods,including single-stage shearing,pre-shearing and multi-stage shearing,are conducted to investigate the residual strength of slide zone soil by employing ring-shear apparatus.It is conducted that the formation of shear band of slide zone soil is relevant with the shear displacement;the residual strength increases with the increasing of effective normal stress.For slip soil sample with a pre-existing shear band,residual shear strength can be soon and easily reached;initial dilatancy phase,contraction phase due to grain migration and constant contraction phase make up shear settlement curves of different ring-shear tests and the changing trend of shear stress in each stage is different.The residual strengths obtained from pre-shearing test and multi-stage test are larger than the actual value;the single stage shearing should be the preferred approach to acquire residual strength of slide zone soil.