A combined analytical-numerical method for groundwater inflow into circular tunnels in drained conditions

Wu, Jian; Zhou, Zhifang; Zhuang, Chao

A combined analytical-numerical method for groundwater inflow into circular tunnels in drained conditions | Une méthode combinée analytico-numérique concernant l’arrivée d’eau souterraine dans les tunnels circulaires pour des conditions drainées Un método numérico-analítico combinado para estimar el aporte de agua subterránea en túneles circulares bajo condiciones de drenaje 一种解析-数值联合方法求解疏干条件下圆形隧洞涌水量 Um método analítico-numérico combinado para a entrada de água subterrânea em túneis circulares em condições de drenagem

2021

Wu, Jian | Zhou, Zhifang | Zhuang, Chao

The excavation and construction of tunnels in drained conditions essentially involves groundwater inflow, which results in water-table drawdown, groundwater inflow rate reduction, and pore-water pressure redistribution. A combined analytical-numerical method is proposed to estimate the groundwater inflow into circular tunnels in drained conditions. The method consists of three semianalytical formulas for shallow, deep, and lined tunnels, based on the trench model and the image method. Then, various two-dimensional cross-section numerical models are built, considering different model parameters like tunnel radius, initial water level, and lining. Based on the numerical results, the effects of the lining on the water inflow rate, drawdown, and water pressure are evaluated, and the semianalytical formulas are obtained by regression analysis. The most interesting finding is that the free surface intersects the tunnel boundary when r/h ≥ 0.062, which is regarded as a criterion for dividing shallow and deep tunnels in this study. The proposed semianalytical formulas, taking into account the effect of the drained condition, can provide better predictions of tunnel inflow compared to existing analytical formulas.

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