甘肃永靖黑方台地区黄土滑坡土的力学性质

An analysis of the soil mechanical properties involved in loess landslides in Heifangtai, Gansu Province

与地下水位以下的饱和黄土力学性质相比,包气带黄土力学性质具有不同的表征参数和测试方法,其对黄土斜坡渗流场和稳定性的影响不容忽视。以甘肃黑方台地区黄土为例,分别采用张力计和轴平移技术量测了黄土的部分区段土-水特征曲线,依据Gardner、Van Genuchten和Fredlund and Xing 3种经验公式对轴平移测试数据进行拟合,获取了完整的土-水特征曲线。基于GDS多功能三轴仪,通过控制基质吸力的三轴剪切试验,获取了考虑基质吸力的黄土强度参数。结果显示:张力计和轴平移技术量测的部分区段土-水特征曲线具有相近的曲线形态,但张力计曲线位于轴平移技术曲线的上方;当基质吸力由100kPa减小至20kPa时,黄土内摩擦角减小约1°,粘聚力下降近22kPa;拟合所得的黑方台地区黄土的基质吸力摩擦角为15.6°。试验为进行黑方台黄土斜坡的非饱和渗流和稳定性分析提供了参数。

Compared with the mechanical properties of saturated loess below the groundwater table, the mechanical properties of loess in the capillary zones have different characterization parameters and testing methods. These differences have remarkable impacts on the seepage field and stability of loess slopes. Hence it is meaningful to derive accurate mechanical parameters of loess in the capillary zones. Taking the loess of Heifangtai in Gansu Province as the study area, the authors adopted both tensiometer and axial-parallel translation technique to test partial soil water content curve of loess of Heifangtai. Three empirical equations, i.e., Gardner, Van Genuchten and Fredlund and Xing, were used to fit the axial-parallel translation technique testing data to derive integrated soil water content curve and fitting parameters. Based on GDS multi-functional trixial apparatus, the authors obtained shear strength parameters of unsaturated loess via trixial shear tests by controlling matrix suction. The test results show that partial soil water content curves derived by tensiometer and axial-parallel translation technique have similar shapes, with the difference that the extensometer curve lies above that derived from axial-parallel translation technique. In the process of decrease of matrix suction from 100kPa to 20kPa, the internal friction angle decreases by about 1°, while the cohesion decreases by 22kPa. The fitted matrix suction frictional angle of Heifangtai loess is 15.6°. The tests provide parameters for unsaturated seepage and stability analysis of loess slopes in Heifangtai.