Evaluation of optimized depth of waterproof curtain to mitigate negative impacts during dewatering

摘要

Dewatering using a combination of waterproof curtain and pumping wells is commonly adopted to ensure the stability of foundation pits in multi-aquifer strata. However, dewatering is likely to result in environmental problems. This paper investigates the impact on surroundings owing to the interaction between the waterproof curtain and pumping wells by numerical simulation. The depth of the diaphragm wall penetrating the dewatering aquifer (D) and the filter length of pumping wells (L) are varied in the simulation. The relationship between approximate hydraulic gradient (Delta i) or ground settlement outside the foundation pit (S) with curtain depth ratio R-D (D over the thickness of the dewatering confined aquifer H-a) or filter length ratio R-L (L/H-a) can be divided into three change parts, namely initial gradual, middle sharp and final gentle part. Three values of R-D and R-L, namely effective, suggested and control value, are proposed. R-D and R-L should vary between the effective and control value. The suggested value of R-D and R-L, is recommended in actual engineering by comprehensive consideration. The effective, suggested and control value of R-D can be calculated by a linear equation according to the value of R-L.