地震动参数对地下洞室安全系数的影响分析

摘要

为解决地震作用下地下洞室围岩安全的定量评价问题,文章建立了一种基于整体安全系数和点安全系数的围岩稳定综合评判方法.首先给出了基于岩体抗剪强度折减原理的洞室整体安全系数计算方法,该方法以主厂房和主变洞之间的塑性区恰好贯通作为洞室整体失稳的临界判据,整体安全系数通过搜索折减系数而得到;然后给出了基于Mohr-Coulomb屈服准则的点安全系数计算方法.结合西南某水电站地下厂房洞室工程,研究了不同地震动输入参数对洞室整体安全系数和关键部位的点安全系数的影响规律.计算结果表明,基于安全系数的地下洞室围岩稳定定量评价方法是可行的,能够反映不同工况下洞室整体安全程度和不同部位的局部安全程度.研究发现,洞室整体安全系数和关键点安全系数均随地震波振幅、持时的增加而减小;随入射角的增加而增大;地震波低频对洞室影响较大,高频则影响较小.%In order to quantitatively evaluate the safety of the surrounding rock of an underground cavern under seis-mic load,a comprehensive evaluation method for the stability of surrounding rock is proposed based on the general safety factor and point safety factor.A calculation method for the general safety factor of a cavern based on the prin-ciple of shear strength reduction of a rock mass is given,the run-through of the plastic zone between the main power-house and main transformer room is presented as a critical criterion for the overall instability of the cavern,and the general safety factor is obtained by searching for the reduction coefficient.A point safety factor calculation method based on the Mohr-Coulomb yield criterion is given.The influence of different seismic input parameters on the general safety factor of the cavern and the point safety factor of key positions are studied based on an underground power-house cavern of a hydropower station in Southwest China.The results show that the quantitative evaluation method for the stability of the surrounding rock based on the safety factor is feasible and can reflect the general safety de-gree and local safety degree of different positions of the cavern for different working conditions.It is found that the general safety factor of the cavern and the point safety factor of key positions decrease with an increase of the ampli-tude and duration of a seismic wave while they increase with an increase of the incident angle; additionally,the low frequency of a seismic wave has a great influence on the cavern while the high frequency has little effect.