Abstract: The calculation of total water inflow of foundation pit is the key of a foundation pit dewatering scheme. In this scheme, influence radius is a parameter of great importance. At present, empirical formulas, empirical values and graphic methods are usually used to estimate the influence radius in the industry. The empirical formula takes the permeability coefficient and drawdown of dewatering well as the main factors to determine the influence radius, while it takes less consideration of other influencing factors into account. The measurement and drawing errors existing in graphic method have great influence on the results. In this paper, a finite element method is proposed to calculate the influence radius based on the principle of minimum total potential energy in the real domain. When the water level of well reaches the control level, taking the original stable water level of the groundwater as the upstream hydraulic head, the water level of the dewatering well as the downstream hydraulic head, the water leaping zone between the control water level and the water level of the well as the escape boundary, and the influence radius as the horizontal distance of seepage field, the calculation of the influence radius can be simplified to the calculation of the horizontal size of the model with the upstream boundary head, the downstream boundary head and the escape boundary known. Two engineering scenarios were calculated using this method. Results obtained were compared with the results of field pumping tests and empirical formula solutions. The results show that the algorithm in this paper can accurately calculate the influence radius. The outcome of this research can be used to improve the calculation accuracy of foundation pit water inflow, make the design of foundation pit dewatering more reasonable, and have potential engineering application value.

Key words: dewatering design of a foundation pit, influence radius, principle of minimum total potential energy in the real domain