非饱和土应力状态变量试验验证研究

Test verification of stress state variables for unsaturated soils

为验证非饱和土两个应力状态变量的合理性,对常规非饱和土三轴仪进行了改进,采用3个压力–体积控制器分别控制孔隙水压力、内室压力和外室压力,提高了量测精度。使用改进的非饱和土三轴仪对描述非饱和土应力状态的两个应力状态变量进行系统的试验验证,做了不同初始干密度、不同初始饱和度、不同初始吸力的3组重塑黄土及1组原状Q_3黄土的各向等压试验,试验中等值改变(增加或减少)总围压、孔隙水压力、孔隙气压力而保持应力状态变量本身不发生变化,通过量测试样体积和水量变化分析检验两个非饱和土应力状态变量的合理性。研究结果表明:对于原状Q_3黄土和各种起始条件的重塑土(包括不同密度、不同饱和度及不同吸力的土样),当只改变应力状态变量的个别组成部分而保持两个应力状态变量本身不发生变化时,则土样的体积变化和含水率变化均很小,可忽略不计。研究结果说明描述非饱和土的两个应力状态变量是合理的,使非饱和土的两个应力状态变量理论有了牢靠的试验依据。

In order to verify the reasonableness of two stress state variables for unsaturated soils and to improve the accuracy of tests, the triaxial apparatus for conventional unsaturated soils has been improved to control the pore water pressure, the inner and outer chamber pressures with three pressure-volume controllers. Using the improved triaxial apparatus, the equal cell pressure compressed tests on remoulded and undisturbed Q_3 loess with different initial dry densities, initial saturations and initial suction is are performed to verify the reasonableness of two stress state variables for unsaturated soils. In the tests, the confining pressure, pore water pressure and pore gas pressure equivalently change while the stress state variables themselves do not change, and then, by the amount of the change of volume and moisture content of samples to verify the reasonableness of the two stress state variables for unsaturated soils. The results show that for the remoulded and undisturbed Q_3 loess, only change the individual components of the stress state variables while the stress state variables themselves do not change, can the change of volume and moisture content of samples be ignored. It is reasonable to describe the mechanical behavior of unsaturated soils by using the two stress state variables, and it gives a large number of experimental data to the theory of two stress state variables for unsaturated soils.