STUDY AND MANUFACTURE OF FLEXIBLE BOUNDARY LOADING TESTING MACHINE
柔性边界加载试验机研制

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.