崩积混合体含水力学特性剪切试验研究

Experimental Research on Shear Behavior of Colluvium with Water

崩积混合体是一种不同于土和岩石的高度非均质材料,其变形和抗剪强度参数受含石率、含水率影响较大.本文通过现场取样,综合考虑这两个因素的影响,开展室内大型直剪试验.研究结果表明:剪切力-切向位移关系曲线表现为五个阶段;随含水率增加,崩积混合体的剪切力-切向位移曲线相对下移,抗剪强度下降;含石率较低(0和20%)时,粘聚力在30%含水率达到最大,含石率较高(40%和70%)时,粘聚力在20%含水率最大.回剪过程中,较低含石率时,粘聚力先减小后增大.较高含石率时,则一直下降.从天然含水率至20%含水率时,摩擦角缓慢下降.当含水率超过20%时,摩擦角随含水率急剧下降;较低法向应力下,混合体试件易剪胀.较高法向应力下,混合体试件易剪缩.

Colluvium is a kind of heterogeneous discontinuous material different from soil and rock whose deformation and shear strength are influenced by the two important factors of rock content and water content.In this paper,by taking on-site sampling and considering the influence of these two factors,a large-scale indoor direct shear test is carried out.The research results show that the shear force-tangential displacement relationship curve has five stages:with the increase of water content,the shear force-tangential displacement curve of the collapsing mixture moves down relatively,and the shear strength decreases;when stone content is low(0 and 20%),the cohesive force reaches the maximum at 30%water content,and when stone content is high(40%and 70%),the cohesive force is maximum at 20%water content.In the process of back shearing,when rock content is lower,the cohesion first decreases and then increases.When stone content is higher,it keeps decreasing.As moisture content changes from the natural state to 20%,friction angle will slowly decrease while it decreases sharply with water content when water content exceeds 20%.In addition,the mixture shows dilation in lower normal stress but shear compression in higher normal stress.