部分排水条件下饱和黏土渐近状态本构模型研究

An asymptotic state constitutive model for saturated clay under partial drainage

为研究排水边界条件对饱和黏土强度特性的影响,利用GDS-DYNTTS动三轴仪开展了饱和黏土的不排水试验和自由排水试验。采用控制体应变与轴向应变增量比ξ的方法进行了部分排水条件下饱和黏土的强度特性试验,从孔隙水压力、p’-q平面的有效应力路径和渐近状态特性等方面研究了排水边界条件对饱和黏土力学特性的影响。基于渐近状态特性和剪胀特性,将应变增量比x引入应力路径本构模型,建立了饱和黏土渐近状态本构方程。通过与孔压、有效应力路径试验结果的对比验证了模型的合理性。试验结果表明:饱和黏土的应变增量比ξ应小于0.3;排水条件影响正常固结黏土剪胀性的发挥程度、有效应力路径以及土的抗剪强度大小。随着应变增量比ξ的增大,饱和黏土的孔隙水压和有效应力比减小而强度增大。试验后期,饱和黏土试样长期处于临界状态,改变排水条件可抑制或加速土体的破坏。

A series of undrained,partially drained and completely drained triaxial tests were carried out to investigate the influence of drainage boundary conditions on the strength characteristics of saturated clay.The partially drained tests were carried out by controlling the strain increment ratio of the volume and axial strains.The tests investigated the influence of drainage boundary conditions on the mechanical properties of saturated clay including the pore water pressure,the effective stress path and the asymptotic behavior of the p’-q plane.Based on the asymptotic state and dilatancy characteristics,an asymptotic state constitutive model for saturated clay was established by introducing the strain increment ratio into the stress path constitutive model.The comparison between experimental results of pore water pressure and effective stress path and simulations demonstrates a good predictive ability of the model.The test results show that the strain increment ratio of saturated clay should be less than 0.3.The drainage condition affects the dilatancy of normal consolidated clay,the effective stress path and the shear strength of soil.With the increase of the strain increment ratio,the pore water pressure and the effective stress ratio of saturated clay decrease but the strength increases.The saturated clay specimen will be in a critical state for a long time,and the change in drainage conditions can inhibit or accelerate the failure of the soil.