陶瓷板和多孔渗透膜对非饱和土三轴试验的影响及其数值模拟

Influence of Different Axis-Translation Technique Using Ceramic Disk /Microporous Membrane on Unsaturated Triaxial Test and Its Numerical Simulation

摘要:

通过陶瓷板和多孔渗透膜两种轴平移技术的非饱和三轴试验，获得了吸力一定时真砂土（完全风化的花岗岩）的应力应变曲线及排水变形特征，并利用有限单元法对三轴试验进行数值模拟。试验结果表明，使用多孔渗透膜时试样的饱和度大于使用陶瓷板时的饱和度，且试样在剪切过程中排水量更小。数值计算得到的试样的应力应变曲线与三轴试验获得的基本一致。剪切过程中，试样内部的吸力和饱和度呈现不均匀分布，与陶瓷板相比，多孔渗透膜可以更好地控制剪切过程中试样的吸力。数值模拟结果表明，非饱和土三轴试验是一个边界值问题而非土体的单元力学行为。

Abstract:

In this paper， an unsaturated triaxial test was conducted on Masado using axis-translation technique （ATT） with ceramic disk/microporous membrane filter （MM filter）. The stress-strain relation and drainage properties in the shear stage was obtained under the constant suction condition. Then， the finite element method （FEM） was utilized to simulate the triaxial test as a boundary value problem. The drained/vented triaxial tests results show that the degree of saturation and the drainage discharge of the specimen with the ATT of the MM filter is different from that of the ceramic disk. The calculated global stress-strain relation basically has a similar tendency as the triaxial test. The suction and the saturation are non-uniformly distributed within the specimen. The ATT with the MM filter is able to control the suction better during the shear stage than that with the ceramic disk. Thus， the unsaturated triaxial test with the ATT would be considered as a boundary value problem instead of an element test.