簸箕山大型老滑坡滑动带的结构特征及形成机制试验研究

 上更新世红色黏土岩是黄土高原大型滑坡的易滑地层，对其滑动带的结构特征及形成机制研究较少。在对黏土岩滑动带的组构、构造特征进行解析的基础上，通过三轴应力–应变试验、残余强度试验及滑带土蠕变试验，分析大型滑坡黏土岩滑动带的形成机制。研究表明：(1) 簸箕山黏土岩滑动带发育密集的近水平剪切面，伴随滑带土结构改变的是塑性变形、剪切变形，运动方式上以块体滑动为主；(2) 黏土岩转变为滑带土后，裂隙增多，平均吸水速率达2.7 g/h，其标准岩样单位时间吸水速率是原岩的1.5倍，活性为0.83，比表面积、活性均高于原岩；(3) 与原岩结构改变相应的是强度的衰减，含水率为19.1%时，黏土岩原岩的峰值强度的黏聚力613 kPa，内摩擦角26.7°，簸箕山滑带土长期强度的黏聚力57.4 kPa，内摩擦角20.47°，残余强度的黏聚力8.79 kPa，内摩擦角为17.2°。

STRUCTURAL CHARACTERISTICS OF SOFT-ROCK SLIP ZONE AND EXPERIMENTAL STUDY OF ITS FORMATION MECHANISM IN BOJI MOUNTAIN LARGE-SCALE OLD LANDSLIDE

The slip zone of large-scale landslide in the Loess Plateau has been identified as red clay rock of Upper Pleistocene. However，there are few studies about the structural characteristics and formation mechanism of the slip zone. Herein，the fabrics and structural characteristics of clay rocks are introduced based on drilling core analysis，surface survey，X-ray diffraction and scanning electron microscope. Meanwhile，stress-strain test，residual strength test and slip zone creep experiment are also implemented. The formation mechanism of interbedded shear zone in the large-scale landslides is therefore analyzed. The results indicate that the main slip zone consists of rich-developed approximately horizontal shear plane. Plastic deformation and shear deformation break out together with the changes of soil structures in the slip zone. As for the mode of motion，block sliding prevail. It is also found that clay rocks suffer more fissures after evolving into soil of slip zone. The average water absorption velocity reaches 2.7 g/h and the penetrability is promoted. Under such a condition，the water absorption velocity of the standard rock sample in unit period accounts for 1.5 times of original rocks；the specific activity is 0.83. It is better than original rocks in terms of specific surface area and activity. Furthermore，structural changes of original rocks are accompanied by strength attenuation. According to test results，the conhesion of peak strength for original clay rocks with water content of 19.1% is 613 kPa，and the internal friction angle is 26.7°. In Boji mountain，the conhesion and internal friction angle of residual strength of slip zone is 8.79 kPa and 17.2°，respectively；the conhesion and internal friction angle of long-term strength of slip zone is 57.4 kPa and 20.47°，respectively.