黄土塬地区非饱和结构性黄土的强度特性研究

为了揭示黄土塬地区非饱和原状及重塑黄土的结构性强度特性的有关规律,完善非饱和土的非线性模型,获得关于黄土塬地区非饱和黄土的变形和强度特性及相关参数,以陇东Q3原状及重塑黄土为对象开展试验研究,对不同初始吸力及不同净围压下的非饱和黄土进行了三轴固结排水剪切试验,研究了黄土塬地区非饱和原状及重塑黄土的变形特性、临界状态、强度参数及吸力变化特性。研究结果表明:原状黄土的剪切破坏表现出明显的剪缩现象,重塑土试样的变形出现剪胀和应变软化现象,剪切变形会出现明显的剪切带现象;不同初始吸力下,原状土偏应力与体应变临界状态线均成线性关系,而非饱和重塑黄土体应变受干密度的影响较大,试验过程中,较大干密度的试样出现了先剪缩后剪胀的现象;非饱和黄土的抗剪强度受基质吸力的影响,非饱和原状黄土的黏聚力随吸力的增大而增大,有效内摩擦角受吸力影响较小,可近似为一常数,非饱和重塑黄土的强度受基质吸力和干密度的影响较大,但对内摩擦角的影响较小;试验得出黄土塬地区非饱和原状及重塑黄土的强度参数,且求得的原状土参数K比重塑土参数K受吸力的影响更大。

Experimental study on strength properties of unsaturated intact loess in loess tableland regions

In order to obtain the deformation and strength parameters and other related parameters of unsaturated intact loess in the loess tableland regions of Gansu Province, the triaxial consolidation drained shear tests are performed on the unsaturated intact loess with various initial suctions and net confining pressures. The deformation characteristics, critical state, strength parameters and suction variation characteristics of unsaturated intact loess are studied under the constant water content. The results show that the shear failure of intact loess belongs to plastic failure and exhibits significant shear contraction phenomenon. Under different initial suctions, the critical states of deviatoric stress and body strain are all linear. The strength envelope of undisturbed loess in p-q plane can be normalized to a straight line, and it can be expressed approximately with the critical state line of saturated soils. The shear strength of unsaturated loess is influenced by matrix suction, and the cohesion of unsaturated loess increases with the increase of the suction. The effective internal friction angle is less affected by the suction, which can be approximated as a constant. The strength parameters of unsaturated undisturbed loess in the loess tableland regions of Gansu Province are obtained. Besides, the parameter K has a great influence on the suction and there is a linear relationship between the parameter K and the suction.