柔性边界加载试验机研制

现有的土力学试验机都是刚性边界加载，也就是等位移边界加载。这种试验机基本上是以研究均匀材料为目的，并且，它主要用于研究材料内部一点的应力-应变状态和强度准则。而实际的土石混合体和破碎岩体内部包含有结构面和节理面等，它们是非均匀、非连续的，在外力的作用下其内部的应力分布是不均匀的。对于这种材料，其真正的受力条件是等应力边界条件。为此，介绍了一种自行研制的三轴试验机——柔性边界加载试验机。该试验装置可以更好地从均匀加载的角度研究非均匀、非连续介质的变形及破坏规律。对这种试验机的原理和设计作了说明；推导出了轴压、围压、半衡压之间的协调关系：同时，还介绍了超声波位移测量系统以及压制试样的装置和压制过程。

STUDY AND MANUFACTURE OF FLEXIBLE BOUNDARY LOADING TESTING MACHINE

Existing testing machines for rock and soil mechanics and geo-engineering are all under stiff boundary loading,that is,all the displacements at every point of boundary surface are equal. These kinds of testing machines are aimed at homogeneous materials. The existing testing machines are mainly used to study stress-strain state and strength criterion at a point inside homogeneous materials. This does not correspond with the fracture patterns of rock and soil mixture or fractured rock. The reason is that these materials contain structural faces and joint faces,and they are inhomogeneous and discontinuous. While external forces are applied on them,the stress distribution inside materials is uneven. For these materials,the real state is that stresses acting on every point of boundary surface are equal. In order to study the mechanical behaviour of rock and soil mixture or fractured rock,a new type of triaxial compressive test machine is developed,namely flexible boundary loading testing machine. This testing machine is good at studying the deformation and failure of inhomogeneous and discontinuous media from the angle of loading equability. The working principle and design thought of this machine are illustrated. The correlation among axial pressure,confining pressure and balance pressure is derived. At the same time,the application of ultrasonic displacement measuring system to flexible boundary loading testing machine and the making process of test sample are also presented.