FAILURE CHARACTERISTICS UNDER HIGH PRESSURE OF FOUR KINDS OF ROCKS TAKEN FROM NORTH CHINA

Experiments of rock failure were made by using the first 1 GPa triaxial high pressure vessel of our country. The samples were of Jinan gabbro, Changpin granite, Fangshan marble and Zhoukoudian limestone. The major results are: (1) In the pressure range corresponding to the crust, for gabbro and granite, brittle failure happens and the strength and the ductility increase with the confining pressure; the fracture angle increases with confining pressure too. Dilatancy takes place before failure and the precursor manifested by increase of AEactivity can be observed. (2) for samples of marble and limestone in the pressure range 0.1-0.8 GPa barrel deformation happens and visible major fault doesnt from. Loading capability increases with deformation and strain hardening takes place. During the process of deformation the level of AEactivity is very low. These experiments characterize that the confining pressure has been raised to a higher level in rock mechanical triaxial experiments, and may have reference value for study of the physics of seismic foci.