Infiltration analysis of perforated storm sewer: Finite difference modelling versus field tests

摘要

Due to urbanization, the ground in cities is often covered with impervious structures. Rainfall infiltration is then limited to cause the prolonged draught-like condition. Combined sanitary and storm sewers need to satisfy the requirements of rainfall runoff, such that urban flooding can occur easily due to insufficient discharge capacity of sewers during heavy rainfalls. Sanitary and storm sewers should be constructed separately, and perforation in storm sewer can enable the occurrence of partial rainfall infiltration to: (1) ease the burden of rainfall runoff, and (2) help the groundwater recharge. In this investigation, the alternating direction implicit method (ADI) is adopted to simulate the infiltration process of stormwater in the ground. Nonlinear second order differential equations for governing equation, initial and boundary conditions are established, and converted into tridiagonal systems of equations. The Thomas algorithm is employed to solve the flow conditions at all discretized nodes. The efficacy of the proposed finite difference method is assessed by comparing against field measurements of cumulative infiltration. Upon the successful calibration of the model, parametric analyses are conducted for design optimization of drainage holes. The opening ratio is suggested at 0.25, such that the drainage performance of perforated sewer can be optimized.