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5·12地震后,震区岩体受到了不同程度的破坏,产生了大量松动岩体,对新建隧道围岩压力产生了较大的影响。为研究地震力对岩体的破坏深度以及震裂松散岩体对隧道围岩压力的影响,基于波动理论和摩尔库伦准则,分析了地震力对岩体破坏的极限深度,推导出解析公式,并通过波速测试结果对震裂松散岩体的松动深度进行了探讨,最后就松散岩体对隧道围岩压力的影响进行了理论分析。研究结果表明:1地震力对岩体破坏有一极限深度,隧道埋深越浅,岩体越易产生破坏;2岩体破坏极限深度与岩体力学参数及地震水平震动速度有关,汶川地震震区岩体的极限破坏深度最大达112m;3汶川地震震后,不同松动程度的岩体分别占破坏岩体深度的20%、30%和50%;4震裂松散岩体对围岩竖向松动压力有较大影响,主要原因为震裂松散体的存在,改变了震后岩体的深浅埋分界深度,在震后松散岩体中修建隧道应按等效埋深来确定深浅埋分界深度。
After the May 12 earthquake, the rock mass in the earthquake area was damaged to various degrees, a large amount of loose rock mass was produced, which had a great impact on the pressure of the surrounding rock of the new tunnel. In order to study the influence of seismic force on the failure of rock mass and the pressure of loose rock mass on the surrounding rock mass, based on the wave theory and Mohr-Coulomb criterion, the ultimate depth of seismic damage to rock mass is analyzed, and the analytical formula is deduced. Through the test results of wave velocity, the loosening depth of loose rock mass was explored. Finally, the theoretical analysis of the influence of loose rock mass on the pressure of surrounding rock mass was carried out. The results show that: 1, the seismic force has a limit depth to the rock mass destruction, and the more shallow the tunnel, the more likely the rock mass is damaged. 2 The ultimate depth of the rock mass is related to the mechanical parameters of the rock mass and the seismic horizontal velocity. The maximum failure depth of the rock mass is up to 112m. After the Wenchuan earthquake, the rock masses with different degrees of loosening account for 20%, 30% and 50% of the depth of the damaged rock mass, respectively; The main reason is the existence of loose body of shock, which changes the depth of the deep and shallow boundary of the rock mass after the earthquake. The depth of the deep and shallow boundary should be determined according to the equivalent buried depth in the tunnel built after the earthquake.