含水率及干密度对桂林红黏土抗剪强度的影响

Effect of moisture content and dry density on shear strength of Guilin red clay

为研究含水率及干密度对桂林红黏土抗剪强度的影响机理,进行了一系列控制含水率、干密度的直剪试验,建立含水率及干密度与抗剪强度的函数关系式。试验结果表明:同一干密度条件下,粘聚力、内摩擦角随含水率的增大整体呈下降趋势;在含水率相同时,随干密度增大,粘聚力减小,内摩擦角增大。分析表明:随含水率增大,具有“水稳定”性的胶结作用减弱,引起粘聚力降低;土中结晶态氧化铁含量高于胶结态时,内摩擦角增大,反之则降低。干密度增大时,重塑土因胶结键断裂后短时间无法恢复,使土颗粒的有效胶结面积的减少程度大于其增多的程度,引起粘聚力下降;干密度的增大会改变红黏土的微观结构模型,土中封闭孔隙的增多会导致粘聚力下降;土样微观结构性随干密度的增大而增强,使内摩擦角增大。

This work studied the influence mechanism of water content and dry density on the shear strength of Guilin red clay.A series of direct shear tests to control water content and dry density were carried out and the relationship between water content and dry density and shear strength was established.The results show that under the same dry density condition,the cohesion and internal friction angles decrease with the increase of water content.When the water content is the same,the cohesion decreases with the dry density,while the internal friction angle increases.The analysis shows that with the increase of water content,the cementation with"water stability"is weakened,causing the cohesive force to decline;when the crystalline iron oxide content in the soil is higher than the cemented state,the internal friction angle increases,and vice versa.When the dry density becomes larger,the remolded soil cannot be recovered after breaking due to the cement bond,so that the effective cementation area of the soil particles is reduced more than the degree of increase,causing the cohesion to decrease.The growth of the dry density can change the microstructure model of the red clay,where the increase of closed pores of the soil leads to a decrease of cohesive force.The microstructure of the soil sample increases with the increasing dry density,resulting in an increase of the internal friction angle.