针对某古滑坡滑动带内的含砂黏土开展了系统的室内环剪试验，研究了粗颗粒含量对滑带土残余剪切性状及残余强度的影响，并根据所研究滑坡的多个相似剖面进行了反分析计算，综合比较了室内环剪试验和反算法得到的残余强度指标，给出了文中研究的古滑坡残余强度的推荐值．结果表明: 环剪试验可以较理想地获得滑带土试样在大剪切位移下的残余强度; 文中研究的滑带土与一般黏性土不同，应变软化特性总体来说不太明显，且粗颗粒含量越高越不明显; 滑带土的粗颗粒含量较高时，随着粗颗粒含量的增加，等效残余内摩擦角呈非线性增高趋势．

Systematic ring shear tests of the sand clay in an ancient landslide were carried out in laboratory to revealthe effect of coarse grain content on the residual shear character and residual strength of slip zone soils,and a backanalysis was carried out with multiple similar sections.Then,the calculated residual strength was comprehensivelycompared with that obtained by laboratory test,with a suitable residual strength of ancient landslide being recom-mended.The results show that (1) the ring shear test is an ideal method to obtain the residual strength under largeshear displacement; (2) different from common clay,the slip zone soil is of no obvious strain- softening character,and the strain softening becomes weaker when the coarse grain content increases; and (3) at high coarse grain con-tent,the equivalent residual internal friction angle nonlinearly increases with the coarse grain content.