干湿循环作用下硫酸盐渍土强度特性试验研究

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。

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

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 angle φ of 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.