干密度和基质吸力对重塑非饱和黄土变形与强度特性的影响

The influence of dry density and matric suction on the deformation and the strength characteristics of the remolded unsaturated loess soils

为解决填方工程沉降和边坡稳定性问题,采用非饱和土三轴仪,对延安新区填方的重塑Q_3黄土,进行3种初始干密度下一系列控制基质吸力的三轴剪切试验,研究重塑黄土的变形和强度变化规律。研究结果表明:初始干密度和吸力对重塑黄土的破坏形态、变形特性和强度特性影响较大;随初始干密度的增大,试样的偏应力–轴向应变曲线逐渐由应变硬化型向理想弹塑性再向应变软化型转变;初始干密度和吸力越大,试样的剪胀性越显著,强度越高;有效黏聚力、内摩擦角和吸力摩擦角均随初始干密度的增加而增大;内摩擦角随吸力几乎不变,而黏聚力随吸力呈线性增加;初始切线杨氏模量和切线体积变形模量均随初始干密度与吸力的增加而提高。根据研究结果提出考虑初始干密度和吸力影响的重塑黄土的抗剪强度参数与非线性模型参数的表达式,可用于预估不同初始干密度、不同吸力下重塑黄土的强度和变形参数,为工程应用和数值模拟提供了依据。

In order to solve the problems of the settlement and stability of high-filled slopes, three-dimensional shear tests were carried out to investigate the behavior of unsaturated soil of different dry densities under controlled suction from Yan＇an new district. The variations of the deformation and strength of the remolded loess soils were studied. The test results show that the dry density and matric suction influence remarkably the damage form and characteristics of the deformation and strength. The stress-strain relation varies from the strain hardening to the ideal elasto-plastic then to the strain softening as the increasing of dry density. The greater the dry density and suction, the more obvious the dilation and the higher the strength. The cohesion, the friction angle of the suction and the internal friction angle increased with the increasing of the dry density. The friction angle of unsaturated loess soil changes little with the matric suction variation, but the cohesion increases linearly with the increasing of matric suction. The initial tangential modulus and the volumetric deformation modulus increased with the increasing of the dry density and suction. An expression for strength and a nonlinear model considering the impact of dry density and suction and values of relevant parameters of the soil are proposed for the predictions of the parameters of the strength and deformation of remolded loess soils under different densities and different matric suctions.