含水率对黄土抗剪强度及边坡稳定性的影响

Effect of water content on the shear strength of loess and stability of slopes

以天水市某不稳定混合型道路边坡为研究对象,现场钻孔取样测定其天然含水率与密度,开展含水率分别为21.0%、25.0%、29.0%的重塑黄土试样直剪试验,探究含水率变化对抗剪强度参数及道路边坡稳定性的影响。首先,分析三种含水率下的(分别为21.0%、25.0%、29.0%)应力应变曲线特征;其次,分析含水率变化对抗剪强度参数的影响;最后,建立边坡稳定性分析模型,探讨了含水量变化和不同坡比对斜坡稳定性的影响。试验结果表明:(1)含水率增加,峰值强度会降低,以垂直压力为400kPa为例,含水率从21.0%增加到25.0%及含水率从25.0%增加到29.0%时,峰值强度分别降低了34.3%、34.8%;(2)含水率从21.0%增加到25.0%时,黏聚力降低了54.7%,内摩擦角降低了12.8%;含水率从25.0%增加到29.0%时,黏聚力保持不变,内摩擦角降低了51.7%;(3)根据数值计算模型,斜坡体的含水量增加,坡体的稳定性系数降低;坡比增加,坡体的稳定性系数降低。

In this paper,an unstable mixed road slope in Tianshui City is taken as the research object,and its natural moisture content and density are measured by on-site borehole sampling,and direct shear tests of remodeled loess specimens with water contents of 21.0%,25.0%and 29.0%are conducted to investigate the effects of water content changes on shear strength parameters and road slope stability.Firstly,the stress-strain curves at three water contents(21.0%,25.0%and 29.0%,respectively)were analyzed;secondly,the effects of water content changes on shear strength parameters were analyzed;finally,a slope stability analysis model was established to explore the effects of water content changes and different slope ratios on slope stability.The test results show that:(1)The peak strength decreases when the water content increases.Taking the vertical pressure of 400 kPa as an example,the peak strength decreases by 34.3%and 34.8%when the water content increases from 21.0%to 25.0%and from 25.0%to 29.0%,respectively;(2)when the water content increases from 21.0%to 25.0%,the cohesion decreases by 54.7%and the angle of internal friction decreases by 12.8%;When the water content increased from 25.0%to 29.0%,the cohesive force remained the same and the internal friction angle decreased by 51.7%;(3)According to the numerical calculation model,the stability coefficient of the slope body decreased when the water content of the slope body increased;the stability coefficient of the slope body decreased when the slope ratio increased.