高应力条件下岩体钻孔变形与地应力关系研究

Study on Relationship between Drilling Deformation and In-Situ Stresses under the High Stress Force

锦屏二级水电站引水隧洞上覆岩体一般埋深1500~2000 m,最大埋深约为2525 m,具有埋深大、洞线长、洞径大的特点,为超深埋长隧洞特大型地下水电工程。最大地应力可达到70 MPa以上,在隧洞开挖过程中,由于存在超高的地应力,局部岩体出现了强烈的岩爆和变形。地应力测试钻孔中经常出现岩饼现象,孔壁则会出现变形甚至塌落,给地应力测试造成很大的困难。通过孔壁周围应力状态的理论分析、钻孔孔内电视摄像、岩石单轴抗压试验成果分析和多种岩体地应力测试方法等研究,证明钻孔变形对地应力测试的影响,及其与岩体地应力之间的关系,找到了消除和减少影响的解决办法,得到在高应力条件下的可靠的岩体原始地应力测试成果。

The general burial depth of water diversion tunnel of Jinping II Hydropower Station is about 1500 - 2000 m and the maximum depth is about 2525 m. It has the characteristics of large depth, long hole line length and wide diameter which is an extra large underground hydropower project. The maximum in-situ stresses can reach more than 70 MPa. In the tunnel excavation process, due to the existence of high ground stress, local rock body appeared strong rockburst and deformation. It often occurs rock cake and hole wall deformed or even collapsed in stress testing, which put great difficulties to the test. Based on the theoretical analysis of the stress state around the hole wall, the television camera in the borehole hole, analysis of the uniaxial compressive test results of the rock, and various test methods of the rock stress, the influence of the borehole deformation on the geostress test and the relationship between the stress of the rock mass are proved. Then solutions are made to eliminate and reduce the impact, and obtain the reliable original rock stress test results under high stress conditions.