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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。
In the course of construction, the tunnel will inevitably lead to the redistribution of groundwater seepage field and the decrease of groundwater level. The commonly used calculation method of seepage flow does not consider the effect of water level reduction. Firstly, numerical analysis is used to analyze the change of seepage field caused by tunnel excavation. Considering the effect of groundwater level reduction on seepage, the analytical formula for reducing water level and seepage after excavation is calculated. The results show that during the tunnel excavation, the pore pressure and the infiltration surface of groundwater gradually decrease with time. The pore pressure changes drastically in the range of 5 times from the tunnel, and the infiltration surface of groundwater level decreases by 26.3% ~ 56.7%. After the seepage field is stabilized, the height of groundwater level reduction is closely related to the tunnel radius and the initial groundwater level, and has little to do with the permeability coefficient of surrounding rock. Comparing with the traditional analytical solution and numerical solution, the proposed analytical formula can easily solve the tunnel Excavation reduces the water level and seepage volume, and at the same time applies to the horizontal distribution and inclined distribution conditions of initial groundwater level.