控制吸力的非饱和土真三轴试验研究

基于西安理工大学的新型真三轴仪,在压力室底座与试样顶盖上分别安装高进气值陶土板与多孔板,从而增加孔隙气压力与孔隙水压力独立控制和量测装置,进而利用轴平移技术对基质吸力进行控制,并且新增水气控制面板和气动二联件对可控制吸力的真三轴仪进行了进一步完善。在此基础上初次尝试对重塑黄土进行了同时控制吸力(s=100 kPa)与净平均应力(p=300 kPa)为常数的真三轴固结排水剪切试验,分析了不同中主应力参数(b=0,0.25,0.5,0.75,1)条件下,各主应变(e_1,e_2,e_3)随偏应力(q)的变化情况;给出了重塑黄土在同时控制吸力与净平均应力路径下p平面上的破坏轨迹,并与Lade–Duncan强度破坏准则和Mohr–Coulomb强度破坏准则的预测破坏线进行了比较。

True triaxial tests on unsaturated soils with suction-controlled condition

Based on the new true triaxial apparatus of Xi’an University of Technology, the pedestal of the pressure chamber is installed with a high-air-entry-value ceramic disk and porous plate is placed on the top of the specimens. Thereby, the pore-gas pressure and pore-water pressure can be independently controlled and measured. Thus the axial translation technique is used to control the matric suction. In addition, the true triaxial apparatus is newly equipped with a water-air control panel unit and the pneumatic duplex pieces, which makes the true triaxial apparatus further improvement to control suction. On this basis, the consolidation drainage true triaxial tests are firstly conducted on the remolded loess with suction and net mean stress controlled condition. During the tests, the matric suction (s=100 kPa) and the net mean stress (p= 300 kPa) are kept constant. The measured curves of variation of deviatoric stress (q) versus major, intermediate and minor principal strains (,,) are analyzed under different intermediate stress parameters (b=0,0.25,0.5,0.75,1). In addition, the failure loci of the remolded loess on -plane are given, and the comparision is made between the experimental results and the predicted failure loci of Lade-Duncan failure criterion and Mohr-Coulomb failure criterion.