黄土洞穴发育条件下滑坡土体性质及其稳定性分析

Analysis of the properties and stability of landslide soil under the development conditions of loess caves

黄土洞穴作为黄土高原区独特的地形地貌,其发生与滑坡特征密切相关,洞穴的发育和演化又受到土性、地层结构等因素影响。本文通过野外调查,在黄土洞穴群诱发的黄土滑坡上选择典型剖面进行室内外实验,分析了黄土洞穴发育条件下滑坡土体的物理力学性质,运用数值模拟探究了黄土洞穴对边坡稳定性影响。研究结果表明:1)北郭村滑坡洞穴区域土体的容重、抗剪强度大于非黄土洞穴区域,孔隙率小于非黄土洞穴区域;滑带土容重最大,孔隙率最小,抗剪强度最低。滑坡发生不久,滑坡体土为扰动土,各项土体参数尚不稳定;洞穴区域土体沉积时间久,土体性质稳定;滑带土各项土体参数与前两者相差较大。2)研究区饱和导水率为0.2mm/min-1.3mm/min,滑坡后缘(洞穴区域)土体渗透系数小于滑坡体土(非洞穴区域)的渗透系数,孔隙率是影响入渗的主要因素;在滑坡后缘,黄土洞穴的渗透系数小于农田,有机质是影响入渗的主要因素。3)北郭村滑坡自然状态下稳定系数为0.7936,属于不稳定状态;洞穴状态下稳定系数0.7291,洞穴的存在降低了边坡的稳定性。

As an unique topography in the loess plateau area,the occurrence of loess cave is closely related to the characteristics of landslides,and the development and evolution of the caves are influenced by factors such as soil and stratigraphic structure.Through field investigation,some typical profiles were selected for indoor and outdoor experiments on the loess landslide induced by the loess cave groups,the physical and mechanical properties of the landslide soil under the development conditions of loess caves were analyzed,and the influence of loess caves on slope stability was explored by using numerical simulation.The results show that:1)The bulk density and shear strength of the soil in the cave area of the Beiguo landslide are greater than that of the non-loess cave area,and the porosity is less than that of the non-loess cave area.The slip zone soil has the largest bulk density,the smallest porosity,and the lowest shear strength.Shortly after the landslide occurred,the landslide soil is a disturbed state and the parameters of the soil are not stable.The soil properties of the cave area are stable due to the long deposition time.The parameters of the soil of the slip zone are quite different from the first two.2)The saturated hydraulic conductivity of the study area is 0.2mm/min^1.3mm/min.The permeability coefficient of the soil on the back edge of the landslide(cave area)is less than that of the landslide soil(non-cave area),and the porosity rate is the main factor affecting infiltration;at the back edge of the landslide,the permeability coefficient of loess caves is smaller than that of the farmland,and organic matter is the main factor affecting the infiltration.3)The stability coefficient of the Beiguo landslide is 0.7936,which is belonged to the unstable state.The stability coefficient of the landslide in cave environment is 0.7291,and the existence of the cave reduces the stability of the slope.