高水压条件下大理岩破坏机理试验研究

锦屏二级水电站深埋隧洞中大理岩洞段处于高水压力和高应力环境中, 该段在施工过程中多次发生严重突水灾害。对该段大理岩的高水压条件岩石力学试验表明, 高水压条件下, 岩石应力-应变曲线在峰值应力附近出现明显平缓段, 应力降大, 岩石峰值强度及脆性破坏后破碎程度随水压力升高而升高, 岩石试件以压致拉裂破坏为主。基于高水压条件下裂纹周边应力解析分析, 认为裂隙中高水压力存在降低了裂隙尖端附近高应力集中效应, 与加载方向一定小夹角范围内的微裂隙尖端附近最大拉应力集中程度接近, 这使得岩石中应变能可进一步积累、压致拉裂型微裂隙数量进一步增加, 岩石呈脆性破坏, 并且破碎程度明显增加。研究工作对深埋隧洞突水灾害防治及强降雨诱发高速滑坡灾害预防具有重要的理论和现实意义。

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.