结构性黄土扭剪特性及联合强度破坏应力修正算法

Torsional shear property and algorithm of failure stress in joint strength of structural loess

中国西北地区存在大量的陡峭黄土边坡,降雨或扰动均会导致黄土的结构性大大降低,可能导致滑坡的产生。通过新型扭剪强度测试仪分析了结构性黄土在扭剪试验过程中的破坏特征,基于扭剪试验结果对可以综合考虑结构性黄土抗拉及抗剪特性的联合强度公式进行了验证,并基于联合强度研究了土体破坏应力的修正算法。结果表明,原状黄土、重塑黄土的破坏扭矩随含水率增大而逐渐减小,且原状黄土的破坏扭矩大于重塑黄土;扭剪强度试验中破坏应力圆与联合强度破坏线相切,验证了联合强度公式具有合理的试验基础;基于联合强度提出的土体破坏应力修正算法,可为黄土边坡灾害评价提供更加切合实际的强度理论。

There are a large number of steep loess slopes in the northwestern region of China. The loess structure would be greatly reduced by rainfall or disturbance, which may lead to the occurrence of landslides. Therefore, it is of great theoretical significance to carry out the researches on torsional shear strength test and tensile strength test of structural loess. In this paper, firstly, the failure characteristics of structural loess are analyzed using a newly developed test device for torsion shear test. Secondly, based on the results of torsional shear test, the joint strength formula which can comprehensively consider the tensile and shear properties of structural loess is validated. Finally,an algorithm of calculating failure stress is derived based on the joint strength. The results show that the failure torques of intact loess and remolded loess gradually decrease with the increase of water content, and the failure torque of intact loess is greater than that of remolded loess. In the torsional shear test, the failure stress circle is tangent to the joint strength failure line, which verifies that the joint strength formula has a reasonable experimental basis. The joint strength and the derived algorithm of calculating failure stress can provide a more realistic way for the evaluation of loess slope disasters.