充水节理岩体中大断面隧洞开挖的数值模型研究

Study of numerical model for large tunnel during construction process in water filling jointed rock mass

采用非饱和的渗流应力耦合模型分析了糯扎渡水电站2#导流洞的开挖过程,导流洞部分洞身穿过节理带,洞项水头较高。详细地讨论了高水头和节理带对施工过程的影响。节理带采用描述高密度平行节理组的各向异性节理本构来逼近;考虑开挖引起的介质变形对渗透系数的影响;考虑排水引起的饱和度变化对渗透系数的影响。所用的非饱和瞬态耦合模型可以模拟出开挖引起的 EDZ 区域孔隙水压力急剧升高、有效应力减小、渗透系数动态的变化以及排水对洞室稳定性的提高。数值模拟的计算结果与国外类似试验的一般性观测结论相吻合,因此,可以用来评价水位以下隧洞施工方法和施工速度的合理性和经济性。

Coupled hydromechanical model of unsaturated media is used to analyze the diversion tunnel #2 excavation located at the Nuozaidu Hydropower Station in China;part of tunnel site in jointed rock mass zone and water pressure around the tunnel is high. The effects of high water pressure and jointed rock mass zone during tunneling are discussed in detail.The jointed rock mass zone contains two sets of high density of parallel joints,which could be simulated by anisotropic joint constitutive model. Excavation-induced permeability changes and draining-induced saturation and permeability changes are taken into consideration. The transient coupled hydromechanical model could simulate a rapid local pressure increase,effective stress decrease,permeability changes and stability improves on excavation disturbed zone (EDZ) around tunnel during construction.Results from numerical model matches some similar foreign general experiment conclusion;and the model could be used to assess rationality and economical efficiency of tunnel construction under high water pressure condition.