黄土-红粘土接触面滑坡上部黄土渗透性较强，下部红粘土渗透性较弱，雨水易在接触面产生汇集，形成易滑带。在对陕西省府谷县脑畔梁滑坡实际勘查中发现，滑坡的滑动面存在一定的厚度，并非完全位于黄土-红粘土接触面，还存在于接触面附近的黄土与红粘土内。因此本文以府谷县脑畔梁滑坡岩土体为研究对象，通过土工试验、数值模拟分别对不同含水率、不同围压和不同接触角度下黄土-红粘土接触界面的力学特性及破坏特征进行研究，结合实际滑坡中不同倾角和不同埋深下黄土-红粘土接触界面的变形破坏方式，探究黄土-红粘土型滑坡接触界面力学特性及破坏特征，取得的研究成果如下：
(1) 通过室内试验研究黄土、红粘土基本物理力学特性可知：随着含水率的增大，黄土的粘聚力与内摩擦角持续降低，红粘土的粘聚力先增大后减小、内摩擦角逐渐减小；与黄土的抗剪强度相比红粘土粘聚力更大，内摩擦角更小。
(2) 通过对接触试样进行室内三轴剪切试验和数值模拟三轴剪切试验，发现随着含水率的增大、围压的减小以及黄土-红粘土接触角度的增大，试样的破坏方式由红粘土鼓胀破坏向试样整体鼓胀破坏再到黄土鼓胀破坏转变。
(3) 接触试样的抗剪强度受破坏方式影响较大，当破坏方式为黄土鼓胀破坏或红粘土鼓胀破坏时，接触试样的抗剪强度为完整黄土试样或完整红粘土试样的抗剪强度，当接触试样破坏方式为试样整体破坏时，抗剪强度介于黄土与红粘土之间；通过对接触试样进行受力分析，得出当接触试样的破坏方式相同时，随着接触角度的增大，试样的抗剪强度先增大后减小，接触角度为试样做薄弱面夹角一半时抗剪强度最大。
(4) 基于脑畔梁滑坡野外勘查、失稳破坏过程数值模拟及接触试样的室内试验，分析不同倾角和不同埋深下黄土-红粘土接触界面的变形破坏特征，得出随着接触面倾角的增大、接触面埋深的减小，黄土-红粘土接触面滑坡滑动带形成位置易由接触面及下部红粘土向接触面及上部黄土转变。
 

Because the upper loess of the landslide at the loess-red clay contact surface is highly permeable, and the lower red clay is an impermeable layer, rainwater tends to collect on the contact surface of the loess and red clay, forming a slippery zone. In actual investigation, it is found that the sliding surfaces of this type of landslide are not all located on the loess-red clay contact surface. In this paper, taking Naopanliang landslide and its rock and soil mass in Fugu County as the research object, the mechanical properties and failure characteristics of loess-red clay contact samples under different moisture contents, confining pressures and contact angles are studied through geotechnical tests and numerical simulations, combined with the deformation and failure modes of the loess-red clay contact interface at different dip angles and burial depths in actual landslides, the formation mechanism of the landslide sliding surface at the loess-red clay interface was explored, and the following main research results were obtained:
(1) The internal friction angle of loess and red clay decreased with the increase of water content, the cohesion of red clay first increased and then decreased with the increase of water content, the cohesion of loess continued to decrease with the increase of water content, and the resistance to loess was higher. Compared with loess, red clay has higher cohesion and lower internal friction angle.
(2) Through indoor triaxial shear test and numerical simulation triaxial shear test of the contact sample, it is concluded that with the increase of water content, the decrease of confining pressure and the increase of contact angle, the failure mode of the sample gradually changes from The bulging failure of red clay transformed into the bulging failure of the whole sample and the bulging failure of loess.
(3) The shear strength of the contact sample is greatly affected by the failure mode of the sample. When the failure mode is bulging failure of loess or bulging failure of red clay, the shear strength is the shear strength of complete loess or complete red clay. When the sample fails as a whole, the shear strength is between loess and red clay; the shear strength of the contact sample is analyzed from the mechanical point of view. When the failure mode is the same, with the increase of the contact angle, the shear strength of the sample first increases and then decreases, and reaches the peak when the contact angle is  .
(4) The instability and failure process of the Naopanliang landslide was simulated, and the deformation and failure characteristics of the loess-red clay interface under different dip angles and burial depths were analyzed. Combined with the formation mechanism of the shear band of the contact sample obtained from the laboratory test and numerical simulation, it is considered that with the contact With the increase of the inclination angle and the decrease of the buried depth of the contact surface, the formation position of the landslide sliding surface at the loess-red clay contact surface is easy to change from the lower red clay to the upper loess.
 

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