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依托某供水工程输水隧洞建立三维数值模型,采用有限差分法和Mohr-Coulomb屈服准则进行施工开挖过程的数值模拟,研究不同围岩条件下隧洞支护时机的估算。首先,基于收敛-约束法进行隧洞开挖推进过程中的变形规律研究,分析监测断面的围岩变形特征,研究发现围岩位移的收敛规律与围岩质量相关,提出隧洞纵向变形曲线的修正公式。然后,采用一步挖穿分期释放的模拟方法,研究监测断面位移随开挖荷载释放的变化规律,以相同的位移释放系数为出发点,构建,开挖面推进距离与荷载释放率之间的关系,并将对应的围岩位移陡增点作为施加支护的推荐时机,得出不同围岩条件下施加支护与开挖面之间的控制距离。研究结果表明,提出的纵向变形公式相关参数确定过程简单,拟合效果良好,推荐的支护与开挖面之间的控制距离符合工程实际规律。
Relying on the water supply tunnel of a water supply project, a three-dimensional numerical model was established. The finite difference method and the Mohr-Coulomb yield criterion were used to simulate the excavation process and to estimate the tunnel support timing under different surrounding rock conditions. First of all, based on the convergence-restraint method, the deformation law of tunnel excavation is analyzed and the deformation characteristics of surrounding rock are analyzed. It is found that the convergence law of surrounding rock displacement is related to the quality of surrounding rock, and the correction formula of tunnel longitudinal deformation curve . Then, the simulation method of one step excavation through staged release was used to study the relationship between the displacement of monitoring section and the release of excavation load, the same displacement release coefficient as the starting point, the relationship between the propulsion distance of construction and excavation surface and the load release rate, And the corresponding point of sudden increase of surrounding rock displacement is taken as the recommended time to apply the support. The control distance between the support and the excavation face under different surrounding rock conditions is obtained. The results show that the parameters of the proposed longitudinal deformation formula are simple to determine and the fitting effect is good. The control distance between the recommended support and excavation face accords with the actual engineering rules.