地下水封洞库洞室轴线方向优化方法

地下水封洞库洞室轴线方向对围岩稳定性、支护费用及施工安全等具有重要影响。基于洞库工程特性,提出了洞室轴向综合优化方法和评价指标。首先,依据国内规范确定出洞室轴向可选范围;然后,基于等效连续介质模型和非连续介质模型,以围岩最大位移、塑性区体积、稳定系数及结构面最大剪位移为评价指标,确定出各模型条件下的最优洞室轴向;基于关键块体理论,以支护压力为评价指标,确定出该条件下的最优轴向;最后,全面分析各评价指标计算结果,综合确定出最优洞室轴向。结果表明:构建的数值模型应包含掌子面,以全面反映施工过程安全性;基于强度折减法确定围岩稳定系数时,使用位移-折减系数曲线的位移突变点作为临界折减系数评判方法较计算不收敛评判法更为合理。将提出的洞室轴向综合优化方法应用于山东某地下水封洞库工程,优化结果证实了该方法的可行性和可靠性,可为相关工程提供参考。

A Method of Optimizing Axis Direction of Underground Water-sealed Storage Cavern

The axis direction of underground water-sealed cavern plays a pivotal role in surrounding rock stability, support costs, and construction safety. We present a comprehensive optimization method together with evaluation indexes for the axis direction of cavern in line with engineering characteristics of underground water-sealed cavern. Firstly, we determined the optional range of axis direction according to specifications in China. Subsequently, we determined the optimal axis direction in equivalent continuum model and in discontinuous medium model, respectively, with evaluation indicators including the maximum displacement of surrounding rock, the volume of plastic zone, the stability coefficient, and the maximum shear displacement on joint surface. Afterwards, we determined the optimal axis direction of cavern with support pressure as evaluation index based on key block theory. Finally, we obtained the optimal axis direction comprehensively through holistic analysis of the calculation result of each index. Research findings suggest that the numerical model should include the excavation face to reflect the safety of construction process. In the determination of stability coefficient of surrounding rock based on strength reduction method, we should select the abrupt change point on the displacement-reduction factor curve as the critical stability coefficient rather than by calculating misconvergence. The present method has been proved to be feasible and reliable in application to an underground water-sealed cavern project in Shandong Province.