隧道渗流场围岩计算边界研究

Study on calculation boundary of surrounding rock in tunnel seepage field

以地铁马蹄形暗挖区间计算为例,首先通过FLAC3D建模,基于BIOT固结方程计算,将不同模型尺寸作为计算工况,模型水平宽度与底部深度分别取值为隧道宽度的2倍、2.5倍、3倍、3.5倍、4倍、4.5倍、6倍,研究不透水边界及透水边界情况下,隧道拱脚水压力、拱顶位移变化及边界范围取值。然后,计算不同模型边界,总结不透水边界及透水边界的模型边界范围,优化模型大小,提高模型计算效率。最后,根据计算结果分析,透水边界与不透水边界下的计算结果相差较大;边界范围对透水边界下的拱脚水压力与拱顶位移收敛值影响较小,对不透水边界下的拱顶位移收敛值影响较大;透水边界条件下计算边界范围h/d与l/d建议均取值为4.5;不透水边界条件下,建议依据实际工程中阻断隧道水力联系的范围进行具体的计算分析。

Take horseshoe shaped mining tunnel calculation as an example,firstly,by computing FLAC3D modeling foot of the tunnel wall,the calculation is conducted using BIOT consolidation equation by changing the size of the modeling for thorough calculation and analyzing the results,under the horizontal width and bottom depth of the model are taken as 2 times,2.5 times,3 times,3.5 times,4 times,4.5 times,and 6 times the tunnel width,respectively,to study the water pressure at tunnel wall feet and displacement of arch crowns boundary value range under permeable and impermeable boundary conditions.Then,calculate different model boundaries,summarize the model boundary ranges of impermeable and permeable boundaries to optimize the previous model scale and improve model calculation efficiency.In conclusion,the calculation result of displacement of tunnel under the permeable boundary and the impermeable boundary are quite different;the change of boundary condition has litle influence on the water pressure at tunnel wall feet and the displacement of arch crowns under the permeable condition,whereas the change of boundary condition has larger impact on structure under impermeable conditions.The results also suggest that the recommended geometry ratio for height over thickness should range around 4.5 for permeable conditions;for impermeable condition,it is recommended to conduct specific calculation and analysis based on blocking the hydraulic connections of the tunnel in actual engineering field.