EXPERIMENTAL STUDY ON FAILURE MECHANISM OF MARBLE UNDER HIGH WATER PRESSURE

Marble under the environment of high water pressure and high stress are present in the deep buried tunnel of Jinping-II Hydropower Station. Several serious tunnel gushing hazards occurred at the marble sections during the construction process of the deep buried tunnel. Marble mechanical test under high water pressure indicates that a flat section appears near peak stress on the stress-strain curve. The stress drop is very big. Rock peak strength and degree of crushing after brittle failure increase with the increasing of water pressure. Compression cracking is the main failure pattern of marble samples. Stress analysis around cracks suggests that high water pressure in cracks reduces the stress concentration effects near crack tip, and the approximately equal concentration effects of maximum tensile stress near crack tips within a small angle range from loading direction. Therefore, the strain energy and the compression-cracking micro-crack quantity in the marble can further increase. The brittle failure can be developed. The degree of crushing of rock is significantly increased. This study has important academic and practical significances for the prevention of deep buried tunnel gushing hazards and high speed landslide hazards induced by heavy rainfall.