厦门地区非饱和残积土的强度随含水量变化规律

VARIATION OF THE SHEAR STRENGTH OF XIAMEN UNSATURATED RESIDUAL SOILS WITH WATER CONTENT

采用普通应变控制式直剪仪对非饱和残积砂质黏性土和黏土进行慢剪强度试验,试验结果表明,砂质黏性土的黏聚力和内摩擦角均对含水量变化敏感,黏聚力随含水量的变化呈二次抛物线关系,内摩擦角随含水量增大呈幂函数减小;含水量对黏土强度的影响主要是降低了黏聚力,对内摩擦角影响很小。黏聚力随含水量的增加呈指数减小。针对上述变化规律,分别建立实用的强度经验公式,避免了吸力量测和计算困难。对提出的强度公式进行试验验证,计算预测强度并与实测强度相比较,结果表明不同竖向应力条件下,高竖向应力下强度的预测精度更高。2类残积土的强度公式预测精度均满足工程要求,可为工程实际应用提供参考。

Shear strength of unsaturated sandy and clay residual soils were conducted by consolidated-drained shearing method using the conventional strain controlled direct shear apparatus. Results show that the shear strength of two kinds of residual soils decreases with increase of water content. The initial water content has effect on both cohesion and frictional angle of sandy clayey soils. The relationships between cohesion,frictional angle and water content of sandy clayey soils are quadratic and power respectively. While the initial water content has negligible effect on friction angle of clay. The considerable influence of increasing water content on shear strength of residual clay is decreasing the cohesion. The variation of cohesion with water content can be described by an exponential relationship. On the basis of variation of shear strength indexes with water content,two new strength formulas of unsaturated sandy clayey and clay were established without suction component and were demonstrated by further tests. Comparisons of the calculated and measured shear strength show that the accuracy of the prediction is higher under high vertical stress. Two strength formulas can provide the good estimation of shear strength of unsaturated residual soils in Xiamen for engineering application.