围岩非均质性对隧道突涌水的影响分析

Analysis of influence of surrounding rock heterogeneity on water inrush in tunnel

受开挖扰动或地应力的影响,围岩非均质性是普遍存在的,此时将渗透系数视为定值会降低涌水量预测精度。针对此问题构建考虑围岩非均质时隧道突涌水计算模型,基于渗流平衡微分方程及达西定律,推导了涌水量及结构外水压力计算公式,并利用泰勒公式及级数展开定理对解析公式进行退化验证,在此基础上对公式的适用性进行了分析,最后通过与现场实测数据对比检验了模型及公式推导的正确性。研究表明:降低开挖扰动程度,可减弱隧道围岩渗透系数的变异性,对提高隧道阻水能力有积极作用;考虑开挖扰动对围岩渗透系数的影响时,支护结构外缘水头高度计算误差可由14%降低到6%;考虑地应力对围岩渗透系数影响时,涌水量计算误差可由18.2%降低为10.6%,一定程度上提高了预测精度。

Affected by excavation disturbance or in-situ stress, the heterogeneity of surrounding rock is universal. Therefore, treating the permeability as a constant will reduce the accuracy of water inflow prediction. In view of this problem, a calculation model of water inrush in tunnel considering the heterogeneity of surrounding rock is constructed. Based on the equilibrium differential equation for seepage and Darcy’s law, the calculation formula of water inrush and external water pressure of the structure is derived. Taylor’s formula and its series expansion are used to degenerate and verify the analytical formula, and then the applicability of the formula is also analyzed. Finally, this model and the formula derivation are verified by comparing results with the measured data. Research shows that the decrease in the excavation disturbance can reduce the variability of the permeability of the surrounding rock of the tunnel, which can improve water resistance of the tunnel. Considering the influence of excavation disturbance on the permeability of the surrounding rock, the calculation error of the water head height at the outer edge of the supporting structure can be reduced from 14% to 6%. Considering the influence of ground stress on the permeability of the surrounding rock, the calculation error of water inflow can be reduced from 18.2% to 10.6%, which improves the prediction accuracy to a certain extent.