干湿循环作用下硫酸盐渍土强度特性试验研究

Experimental Study on Shear Strength Characteristics of Sulfate Saline Soil under Dry-wet Cycles

宁夏地区硫酸盐渍土在夏季的多雨高温时节经历干湿循环过程,土体强度劣化。为探究干湿频次、含盐量对土体强度的影响,采用不固结不排水三轴剪切试验测定配置试样的黏聚力с和内摩擦角φ,探究其变化规律,结合扫描电子显微镜技术分析试样强度劣化机理。试验结果表明:硫酸盐渍土试样的应力应变曲线随干湿次数、围压及含盐量的增加,由应变软化型逐步向应变硬化型过渡;试样的内摩擦角均随干湿次数和含盐量的增加而减小,且含盐量越高,经历的干湿循环次数越多,内摩擦角降幅越大;干湿循环初期(1~3次),黏聚力随含盐量增加而增大。干湿循环后期,含盐量在0%~2%区间,黏聚力随含盐量的增加而减小;而在2%~5%区间,黏聚力随含盐量的增加而增大。随含盐量的增大,干湿循环作用下硫酸盐渍土整体强度逐渐降低,且含盐量越高,特征越明显。

The sulfate saline soil in Ningxia area experiences dry-wet cycles during the rainy and high temperature in summer,and the soil strength deteriorates.To explore the effect of dry-wet cycles and salt content on the shear strength of soil,the non-consolidation and undrained triaxial shear test was used to determine the cohesion force and the internal friction angleφof the sample.And the regular pattern was summed up,the Scanning Electron Microscope was carried to analyze degradation mechanism of soil.The results as follows:With the increase of dry-wet cycles,salt content and confining pressure,the stress-strain curves of the soil gradually changes from strain-softening to strain-hardening behavior.The internal friction angle tends to decrease with the increase of dry-wet cycles and salt content,and the higher the salt content and the more dry-wet cycles are,the more the internal friction angle decreases.The cohesion tends to increase with the increase of salt content at the initial stage of 1~3 cycles.After 3 cycles,the cohesion tends to decrease with the increase of salt content from 0%to 2%,but it increases in the range of 2%~5%.With the increase of salt content,the total strength of soil under dry-wet cycles decreases,the characteristics is more obvious with the higher salt content.