Abstract: The wall-well system could effectively decrease the discharge inside or drawdown outside the foundation pit that comprising suspended waterproof curtain and dewatering wells. Foundation pit is assumed to be a large partially penetrating well with the same area. Based on the assumption that flow into the well is equal to the vertical flow inside the waterproof curtain, an equation is established to calculate the discharge inside and drawdown outside the pit. The discharge calculated by the proposed equation is close to that by simulated results while L/M > 0.6 and r/M < 2.0. It is showed that the calculated discharge is slightly larger than those by numerical analysis or case history. This phenomenon may be attributed to the neglection of energy loss during the flow direction change. Then the influence of some factors including the ratio between horizontal and vertical permeability coefficients, the foundation area and the curtain length is studied. Parametric analyses show that the discharge inside or drawdown outside the pit can be determined by the degree of flow field approaching vertical flow. The proposed equation is suitable for preliminary analysis of decompression dewater when cutting off confined aquifer is difficult.

Key words: confined water, dewatering, waterproof curtain, partially penetrating well, permeability coefficient