圆形隧洞渗流量计算的解析方法及其应用

Analytical method for calculating the groundwater inflow of circular tunnel and its application

隧洞在施工过程中,必将导致地下水渗流场的重分布和地下水位线的降低,当前常用的渗流量计算解析方法未考虑水位降低这一影响。首先通过数值计算方法分析隧洞开挖带来的渗流场变化,考虑地下水位线降低对渗流量的影响,提出分别计算隧洞渗流场稳定后开挖降低水位和渗流量的解析公式。结果表明:隧洞开挖过程中,洞周孔压和地下水浸润面随时间逐渐降低,在距离隧洞5倍洞径范围内孔压变化剧烈,地下水位线浸润面降低幅度达到26.3%~56.7%;渗流场稳定后地下水位线降低高度与隧洞半径和初始地下水位密切相关,与围岩渗透系数关系不大;经过与传统解析解和数值解的对比可以看出,提出的解析公式能够方便求解隧洞开挖降低水位和渗流量,且同时适用于初始地下水位线水平分布和倾斜分布条件。

During the construction of tunnel, the excavation process would lead to the groundwater seepage field redistribution and groundwater level drawdown. However, the effect of excavation-induced groundwater level drawdown on tunnel inflow had not been considered in common analytical method. Through the numerical calculation, the change of seepage field after tunnel excavation is analyzed. And based on the numerical solution, the analytical method for calculating the tunnel inflow and lowered water level is proposed by considering the effect of groundwater level drawdown. The results indicate that the pore water pressure around the tunnel and the water level gradually decrease over time during the excavation process. The pore water pressure changes dramatically in the scope of 5 times tunnel diameters and the water table reduces by 26.3% to 56.7%. After the seepage field stabilization, the lowered water level is closely related to the tunnel radius and initial water level, not to the permeability of surrounding rock. Compared with traditional analytical solution and numerical solution, the analytical method proposed can conveniently solve the lowered water level and tunnel inflow for the cases with horizontal and inclined groundwater level.