非饱和黏性土直剪强度特性及其修正分析

为研究非饱和黏性土的直剪强度特性,采用非膨胀土及两种不同干密度的弱膨胀土进行了包含低应力状态下8种不同上覆压力的直剪试验。试验结果表明,随着上覆压力的增大,最大剪应力及所对应的剪切位移逐渐增大,试验中低应力状态下测定的土体凝聚力小于高应力状态,且试验中的上覆压力对膨胀性土凝聚力的影响大于非膨胀性黏土;而低应力状态下测定的土体内摩擦角大于高应力状态。对直剪试验中上下盒接触面积减小对抗剪强度参数测定的影响进行了分析,分析表明,接触面积减小对抗剪指标有影响,但极其微小。提出对膨胀土边坡浅层破坏进行稳定性分析时应采用低应力下的抗剪强度参数。

Direct shear strength characteristic and modification analysis of unsaturated cohesive soil

In order to investigate the effect of sandy soil gradation on its shear properties, direct shear tests were conducted for four types of different artificial gradation of sandy soil samples made of the standard sand. The numerical shear tests were conducted for DEM samples that have the same gradation with the four artificial sand samples. The test results show that the influence of particle gradation on the internal friction angle is significant; generally, the internal friction angle increases with the non-uniformity coefficient, and decreases with the curvature coefficient. The DEM tests show that the initial sandy soil gradation has significant effect on the porosity ratio, particle coordination number and the particle slide fraction; in addition, the failure of sandy soil is a progressive process that depends on the particle gradation; the dilatancy coefficient decreases at the beginning and increased later with increase of the parameters of d10, d30and d60.