干湿循环作用下钢-土界面剪切特性试验

Experimental study on shear characteristics at steel-soil interface with drying-wetting cycles

为研究干湿循环作用下钢-土界面剪切特性对钢护筒嵌岩桩周土软化变形规律的影响,通过改进的室内直剪试验,设计一定含水率、干密度、级配的初始试样,进行了初始状态和4次干湿循环共5组工况的试验,依次在50 k Pa、100 k Pa、150 k Pa和200 k Pa这4种法向应力条件下进行钢-土界面和土体本身的剪切试验。试验结果表明:干湿循环对土体本身的影响大于对钢土界面抗剪强度的影响;钢-土界面剪切过程中应力-应变关系呈弹塑性变化,没有出现应变软化现象;钢-土界面和土体本身摩擦角变化不大,而黏结力呈先增大后减小的变化趋势。

In order to study the influence of the shear properties at the steel-soil interface with drying-wetting cycles on the softening deformation of soil around the steel-casing rock-socketed pile, initial samples with a certain moisture content, dry density, and gradation were designed. And shear tests on the steel-soil interface and soil body were carried out in five cases, including a initial state and four different numbers of drying-wetting cycles. In each case, samples were subjected to four vertical pressures:50 kPa, 100 kPa, 150 kPa, and 200 kPa. The results show that the influence of drying-wetting circles on the shear strength of soil is greater than that on the shear strength of the steel-soil interface. During the shear process, there is an elastic-plastic stress-strain relationship, and no strain-softening phenomenon occurs at the steel-soil interface under drying-wetting circles. With the increase of the number of drying-wetting circles, the friction angles of the steel-soil interface and soil change little, while their cohesive forces increase first and then decrease.