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为了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,提高了量测体变和含水率的精度;用加荷器施加轴向荷载,可以方便地控制偏应力。在笔者前期用各向等压试验验证非饱和土的两个应力状态变量的基础上,使用改进的非饱和土三轴仪和重塑Q_3黄土做了两类验证试验:第一类是两组控制净围压、偏应力和吸力的固结不排水剪切试验,第二类是3组控制净围压和吸力的固结排水剪切试验。在第一类试验中,等值改变(增加或减少)总围压、孔隙水压力和孔隙气压力而保持净围压、吸力和偏应力本身不发生变化,发现试验过程中土样的体积变化和含水率变化均非常小,可以忽略不计。第二类试验的每一组包含两个控制净围压和吸力分别相同的固结排水剪切试验,其中一个试样在固结完成后直接进行排水剪切试验,另一个试样在固结完成后等值增加总围压、孔隙水压力和孔隙气压力而保持净围压和吸力本身不发生变化的条件下进行排水剪切试验,发现二者的抗剪强度、剪切过程中的体积变化、排水量和广义剪应变都分别十分接近,可以认为两两相等。研究结果从变形(包括体应变和剪应变)、水量变化和强度3个方面说明描述非饱和土的两个应力状态变量是合理的,进一步夯实了非饱和土力学的应力理论基础,为非饱和土的两个应力状态变量理论提供了牢靠的试验依据。
In order to verify the rationality of two stress state variables of unsaturated soils, triaxial apparatus of conventional unsaturated soil was improved. Three pressure-volume controllers were used to control pore pressure, inner pressure and outer pressure respectively, Measurement of body mass change and water content accuracy; load imposed by the axial load, you can easily control the deviatoric stress. On the basis of verifying two stress state variables of unsaturated soils with isotropic pressure tests in the author’s previous work, two types of verification tests were carried out using improved unsaturated triaxial apparatus and remolded Q_3 loess: the first type is two groups The control of the net confining pressure, deviatoric stress and suction consolidation undrained shear test, the second is the three groups of control net confining pressure and suction consolidated drainage shear test. In the first experiment, the net confining pressure, suction force and deviatoric stress were not changed by the equivalent change (increase or decrease) of total confining pressure, pore water pressure and pore pressure, and it was found that the volume change of soil sample during the test And moisture content changes are very small, can be ignored. Each group of the second type of test consists of two tests of consolidated drainage and drainage with the same net confining pressure and suction, one of which is directly subjected to the drainage and shear test after consolidation and the other is consolidated After completion of the equivalent increase in total confining pressure, pore water pressure and pore pressure to maintain the net confining pressure and suction itself does not change under the conditions of drainage shear test and found that the shear strength of the two, the shear volume Changes, displacement and generalized shear strain are very close, respectively, can be considered equal to each other. The results of the study illustrate that it is reasonable to describe two stress state variables of unsaturated soils from three aspects of deformation (including body strain and shear strain), water volume change and strength, which further reinforce the stress theory of unsaturated soil mechanics, Soil two stress state variables theory provides a solid test basis.