Experimental study of the influence of the clay content on the gravel soil mass from the upstream area of a debris flow

The clay content of the gravel soil from the upstream area of a debris flow has significant influence on the pore pressure and shearing strength.This is a problem that has to be solved in studying the debris flow initiation mechanism.Based on the three-axial experiment,this paper studies the relationship among the shearing strength,pore pressure,collapsibility and clay content of the sample from Jiangjia ravine of Dongchuan in Yunnan of China.The experiment indicates that(1) when the clay content is 3.75%~7.50%,the collapsibility of the sample is greater and when it is 5%,that of the sample is the maximum;(2) in the UU experiment,the pore water pressure of the samples with 3.75%~7.50% clay content has the greater increase,and in the CD experiment,the pore water pressure of the sample with 12.5% clay content has the greater increase;(3) the gravel soil with 5% clay content is the easiest to demolish;(4) under the same conditions of rainfall and gradient,the gravel soil with 3.75%~7.50% clay content is most likely to motivate a large-scale devastative debris flow.