卸荷条件下粉质粘土变形性状研究

通过室内应力控制的三轴试验研究卸荷条件下土体的应力-应变关系和孔隙水压力变化特征,得到变形模量的确定方法。研究表明:在初始偏压应力固结条件下,无论是轴向压力保持不变而侧向压力不断卸荷,还是轴向压力和侧向压力同时卸荷,其应力-应变关系均表现为较好的双曲线函数关系。而且,侧向固结压力愈大,强度值愈大。在卸荷过程中,随剪切应力的增大和剪切应变的发展,土样呈现剪胀趋势并在后期产生较大的负孔隙水压力。不排水条件下由于负孔隙水压力的存在,土样的表观强度略有增大。

DEFORMATION CHARACTERISTICS OF SILTY CLAY FROM CONTROLLED-STRESS UNLOADING TESTS

The stress-strain relationship and pore pressure characteristics are studied with stress-controlled axial shear tests. Furthermore, the determination method of deformation modulus is obtained. Two kinds of laboratory tests are accomplished under a deviator confining pressure. One is that the lateral pressure is unloaded when axial pressure maintains constant. The other is that the lateral and axial pressures are simultaneously unloaded. The test results show that the stress-strain relationship took on a hyperbolic function. Moreover, the shear strength was increasing with the increase of the lateral confining pressure. In the unloading process, with the increase of deviator stress and the strain, the soil sample took on a dilatancy trend and showed a large negative pore pressure. Besides, the undrained shear strength was increased slightly due to the negative pore pressure.