川西松潘地区裂隙性黄土强度特性试验

Tests on Strength Properties of Fractured Loess in Songpan Area,Western Sichuan

节理裂隙破坏了黄土的结构完整性,影响其力学性质,一定程度上控制着黄土地区滑坡和崩塌等地质灾害的演化进程和破坏规模。为研究裂隙对黄土强度特性的影响,选取川西松潘地区黄土为研究对象,开展了不同裂隙面倾角、含水率和含砂量等条件下的三轴试验。研究结果表明:仅当黄土中的裂隙面倾角与理论破裂角相近时,剪切破裂面才会迁就已有裂隙面发展;裂隙面倾角大小对黄土强度影响明显,裂隙面倾角为0°时,土体抗剪强度最大,接近理论破裂角时最小;不同含水率和含砂量条件下,裂隙性黄土强度特性均存在倾角效应,但随着条件不同而有所变化;裂隙性黄土的黏聚力受含水量和含砂量变化影响较明显,内摩擦角受其影响相对较小。通过预设不同倾角裂隙面的黄土三轴压缩试验来分析裂隙性黄土强度特性的思路,同样适用于古滑坡滑带土强度特性研究,开展滑坡不同部位的滑带土切面三轴试验可以为深入分析古滑坡复活机制提供借鉴。

Fracture surface can affect the integrity and mechanical properties of the soil,and whose mechanical behaviors also control the evolution process and failure scale of soil slides in the loess area. The loess in Songpan of western China was selected to study the influence of fracture surface on the strength characteristics of the loess. The triaxial tests with preset fracture plane were carried out under the condition of different fracture inclination angle,water content and sand content. The results have shown that when the inclination angle of preset fracture plane is close to the theoretical fracture angle,the new shear fracture surface will accommodate and develop along the preset fracture plane,but not in other angles. The shear strength of soil is obviously influenced by the inclination angle of fracture plane,and it is the maximum when the inclination angle is 0° and the minimum when the inclination angle is about theoretical rupture angle. Under the different water content and sand content conditions,the obliquity effect of loess shear strength still exists,but the shear characteristics of specimens with preset fracture plane in different inclination angles are different. The cohesion of specimen with preset fracture plane is sensitive to the changes of water content and sand content,but the friction angle is not sensitive with little changes. The idea,analyzing the strength characteristics of fractured loess by the triaxial compression tests on presetting fractures with different dip angles,is also applicable to study the strength characteristics of sliding zone soil in the ancient landslide. It is pointed out that the similar triaxial test with preset fracture plane of sliding zone soil in different parts of sliding zone can provide some ideas for the study on reactivation mechanism of ancient landslide.