Calculation Of Influence Radius Of Foundation Pit Dewatering Based On The Principle Of Minimum Potential Energy

Design of a dewatering scheme is the key of the groundwater control with an important parameter of radius of influence in excavation engineering.At present,the methods of solving the influence radius mainly include empirical formula and graphic method.The empirical formula only takes the coefficient of permeability and the depth of the well water as the main factors to determine the influence radius.And the graphic method has great influence on the results because of measuring and drawing errors.Two finite element methods are proposed to calculate the influence radius in the master's degree thesis,whose physical meaning is clear and calculation accuracy is high.And the main results are as follows:(1)The calculation model of influence radius of seepage field is established in phreatic aquifer.When the water level of well reaches the control level,taking the original stable water level of the groundwater as the upstream hydraulic head,and the water level of the dewatering well as the downstream hydraulic head,considering the water leaping zone,which is the distance between the control water level and the water level of the well,the influence radius is simplified to the question of solving the horizontal size of the calculating model.(2)Two finite element methods are proposed to calculate the influence radius based on the minimum principle of the total potential energy in the real domain and the minimum principle of the rate of energy loss,respectively.And the corresponding finite element calculation program is compiled by Fortran.In the calculation process,the error limit is taken as + 5%,which is a conservative approach that the radius of influence is smaller and the simplified calculation for water discharge in excavations is larger.(3)Four excavation engineering cases are calculated by the finite element methods,and the results are compared with the pumping test and empirical formulas.The influence radii calculated are 66.4m,107.17 m,75m and 48 m respectively.The influence radii obtained in field pumping test are 63.1m,103 m,74.8m and 45.5m respectively,and the relative errors are 5.2%,1.1%,0.3% and 5.2% respectively.The influence radii calculated by empirical formula are 89.4m,171.67 m,110.1m and 68.6m respectively,and therelative errors are 41.7%,66.7%,47.2% and 50.7% respectively.The results show that the calculation accuracy of the two algorithms proposed is higher than that of the empirical formula method and closer to the field pumping test results.The research results in the master's degree thesis can improve the calculation accuracy of water inflow of excavations,make the design scheme of excavations dewatering more reasonable,and have potential engineering application value.