非饱和南阳膨胀土的剪切强度及其预测

Shear strength of unsaturated Nanyang expansive soil and its prediction

膨胀土是一种随含水率变化而具有吸水膨胀、失水收缩特性的特殊土,与普通黏土相比,含水率对其强度特性影响更为显著.为了探讨含水率对膨胀土强度的影响,对压实南阳膨胀土进行了一系列直剪试验,得到了在相同干密度及不同含水率条件下的抗剪强度.试验结果表明,南阳膨胀土的抗剪强度和黏聚力均随含水率的增大而减小,内摩擦角受含水率的变化影响不大.此外,把宏观饱和度引入Bishop非饱和土强度公式中,对试验结果与修正强度公式的计算值进行比较,结果表明修正后的Bishop非饱和土强度公式可以较为精确地预测出非饱和膨胀土的强度.

Expansive soil is a problematic soil with swelling and shrinkage. Compared with ordinary clay, the strength is clearly affected by water content. To investigate the effect of water content on the strength of expansive soil, a series of direct shear tests on Nanyang expansive soil with different water contents were carried out. Relationship between shear strength and water content at the same dry density was obtained. Test results show that the shear strength and cohesion decrease with increasing water content, and the internal friction angle changes little. In addition, by introducing macro saturation into the Bishop＇s equation for unsaturated soil, the results show that the modified strength equation can well predict strength of unsaturated expansive soil.