黄土的非饱和特征参数与结构性的试验研究

Experimental study of the characteristic parameters and structural behavior of loess

黄土既有非饱和性,又有结构性。本文首先在控制基质吸力条件下进行了原状黄土和重塑黄土的非饱和直接剪切试验,分析了两种结构性状非饱和土的基质吸力对净应力强度指标,Fredlund抗剪强度公式中参数b,以及Bishop抗剪强度公式中参数χ的影响。表明两种土的黏聚力随基质吸力的增大而增大,b和χ均随基质吸力的增大而减小;在相同基质吸力条件下,原状黄土的黏聚力、b和χ均大于重塑黄土。其次,通过无侧限抗压强度试验,测试了不同含水量原状黄土、重塑黄土和饱和黄土的单轴抗压强度,得到了不同含水量下原状黄土和重塑黄土的构度值。最后,探讨了非饱和黄土的构度与基质吸力、净应力强度指标、参数b和χ之间的关系。

Direct shear test of intact loess and remold loess is carried out under control of the matrix suction. The effect of matrix suction on the net stress strength index, parameter Фb in the Fredlund shear strength formula and parameter X in the Bishop effective stress formula for unsaturated soils were analyzed. The experimental results show that net stress strength index increases when matrix suction increases, while Фb and X decrease, and at same matrix suction, the net stress strength index, Фb and X for intact loess are all lager than those for remold loess. Besides, the unconfined compressive strengths of intact loess, remold loess and saturated loess were measured by the axial compression instrument. According to the definition, the structural indexes of intact loess and remold loess with different water contents were obtained by using the unconfined compressive strength. Finally, the changing relationships between net stress strength index and parameters Фb , X with structural index were also explored.