关中西部大型黄土滑坡滑带土的物理力学特性研究

Study on Physical-Mechanical Properties of Sliding Soil of Large-Scale Loess Landslides in Western Guanzhong

选取宝鸡市金台区为研究区域,通过对比分析三门组黏土与三趾马红土2类滑带土的成分、结构、物理及力学性质,揭示滑坡发生的物理力学特征。对两类滑带土取样,通过移液管全分散法分析两类黏土黏粒含量,并进行黏土矿物X射线衍射定量测试,经扫描电镜放大观察微观结构,用威廉姆斯膨胀判别法判别膨胀性,采用105℃恒温烘干后的试样和天然含水量2种试样,放入注入清水的容器中进行崩解性试验,在天然和饱和2种状态下进行室内慢剪试验。结果表明,二者均属于中等—强膨胀性土,遇水易崩解;两类黏土峰值强度和残余强度差异大,粘聚力平均降低2/3,含水量对其强度影响明显,饱和状态下,内聚力较天然状态降低30%,内摩擦角降低25%。说明滑坡发生时,黏土的峰残差值形成较大的下滑推力,导致滑体沿着滑床面瞬间高速滑动。

We selected Jintai District of Baoji City as the study area to reveal the physical and mechanical characteristics of landslide by comparison and analysis of the composition,structure,physical and mechanical properties with two kinds of sliding zone soil：Sanmen group red clay and Hipparion laterite.We sampled of two kinds of sliding zone to analyze the clay contents of two kinds of clay soils by pipette the dispersion method,and to do the X-ray diffraction quantitative test for clay minerals,to observe the microstructure after amplification by scanning electron microscopy,to discriminate the expansibility with Williams expansion criterion,to do the disintegration test with one sample after drying with 105℃constant temperature and the other sample with natural water content,and to do the indoor slow shear test in both natural and saturated state.The results show that these two kinds of clay soils belong to the medium to strong expansive soil,easily collapse after wetting.There is a great difference between the peak strength and residual strength of two kinds of clay soils.Cohesion is an average reduction of 2/3,and the strength has obvious effect with containing water.The cohesive force decreased by 30% and the internal friction angle decreased by 25%,showing that the peak residual value of the clay causes the larger down thrust when landslides occurs,and leads to instant sliding at high speed sliding along the sliding bed surface.