椭圆应力路径下饱和软黏土循环单剪试验

Cyclic Simple Shear Tests on Saturated Soft Clay Subjected to Ellipse Stress Path

为了研究水平剪切应力对土体动力特性的影响,采用多向循环单剪仪模拟地震时土体所受的水平剪切作用,对温州饱和黏土进行一系列不排水剪切试验,分析在双向应力幅值为1∶2时,当X向和Y向加载波形的相位差分别为0°,30°,60°和90°,循环应力比分别为0.14,0.20,0.25时,相位差和循环应力比对土体动应变、动孔压、动剪切强度及剪切后再固结变形特性的影响。试验结果表明:在循环应力比较小时,应变和孔压比发展较慢,且再固结后产生的沉降也较小;当循环应力比为0.20时,相位差的增大会加快应变和孔压比的增长,X向应变的发展会受到Y向应变的影响,且相位差越大,土体达到破坏所需的圈数越少;当循环应力比为0.25时,相位差对应变、孔压比和强度的影响不明显;循环次数相同,随着循环应力比的增加,应变及孔压的发展速度增快;在一定的循环应力比下相位差越大,双向所产生的应变也就越大,且X向应变的发展会受到Y向应变的影响;当循环应力比为0.14时,再固结后的轴向变形很小;当循环应力比为0.20时,相位差越大产生的轴向变形也越大;当循环应力比为0.25时,相位差对再固结后的轴向变形影响不大。

In order to investigate the influence of horizontal stress on dynamic properties of soft clay, a set of undrained tests with the multi-directional cyclic simple shear apparatus on saturated soft clay were conducted to simulate the horizontal shear stress of soil under the earthquake. Then the influences of phase differences and cyclic shear stress ratios on soil dynamic strain, dynamic pore pressure, dynamic shear strength, deformation characteristics of reconsolidation after shear were analyzed when two-way stress amplitude was 1：2 and phase differences along X, Y direction were 0°, 30°, 60° and 90° respectively, with cyclic stress ration of 0.14, 0.20, 0.25, respectively. The results show that when the cyclic shear stress ratio is small, the shear strain and pore pressure ratios develop slowly and the reconsolidation subsidence is small. When the cyclic shear stress ratio is 0. 20, the shear strain and pore pressure ratios increase with the increase of the phase difference. The development of shear strain in Y direction influences the strain in X direction, and the cyclic number of failure decreases with the increase of the phase difference. When the cyclic shear stress ratio is 0.25, the phase difference has little influence on the shear strain, pore pressure and strength. At the same cycle number, the development rate of strain and pore pressure increases with the increase of cyclic stress ratio. Under a certain cyclic stress ratio, the larger the phase difference is, the larger the strain will be. In the meanwhile, the development of the strain along X direction is affected by the strain along Y direction. When the cyclic shear stress ratio is 0. 14, the axial deformation is small after the reconsolidation. When the cyclic shear stress ratio is 0.20, the axial deformation increases with the increase of phase difference. When the cyclic shear stress ratio is 0.25, the influence of the phase difference on the axial deformation under reconsolidation can be ignored.