黏粒含量对磁县段膨胀土抗剪强度影响的试验研究

摘要

In order to study the effect of clay content on the shear strength of expansive soil,this paper conducts quick shear,saturated quick shear,saturated consolidated quick shear and repeated direct shear tests with electric strain controlled direct shear apparatus,residual shear test,and direct shear/residual shear test apparatus on the undisturbed expansive soils at Ci County Hebei of South-to-North Water Diversion.The soils have different clay contents.Studies show that:in the direct shear test,the shear strength of the expansive soil significantly reduces after the soil is saturated,and increases after it is consolidated.The effect of saturation on the strength of the expansive soil of larger clay content is more significant.The "cure"effect of consolidation on the strength of weak expansive soil of lesser clay content is more significant.As the clay content increases,the cohesion gradually decreases,and internal friction angle first decreases and then increases.The critical value is about 32%.In the repeated direct shear test,the shear strength after peak intensity increases as the clay content increases.The change trend is relatively flat.The residual strength τr decreases exponentially as the clay content increases.While the internal friction angle φr of the residual strength has a logarithmic relation with clay content.The cohesion cr has an irregular relation with the clay content.%利用电动应变控制式直剪仪及直剪/残余剪切试验仪对南水北调磁县段不同黏粒含量的原状膨胀土进行快剪、饱和快剪、饱和固结快剪和反复直剪试验,研究黏粒含量对其抗剪强度的影响.研究表明:饱和后试样的抗剪强度明显降低,固结后强度提高,且饱和作用对黏粒含量较大的中膨胀土强度的削弱作用更为显著,固结作用对黏粒含量较小的弱膨胀土强度的"治愈"作用更显著;随黏粒含量的增大,黏聚力逐渐减小,内摩擦角则先减后增,其临界值在 32%左右;峰值强度后的抗剪强度降低幅度随黏粒含量的增加而增大;土体的峰值强度 τf随黏粒含量则先减后增,变化趋势比较平缓;残余强度 τr 随黏粒含量增加逐渐减小,成指数关系;残余强度内摩擦角 φr 与黏粒含量成对数关系,黏聚力 cr 则比较离散.