Evaluation of the blocking effect of retaining walls on groundwater seepage in aquifers with different insertion depths

• We conducted a series of laboratory tests to investigate the blocking effect of retaining walls on groundwater flow.
• Numerical simulation was conducted to analyze the test procedure and the parameters were determined.
• Numerical simulation was applied to the deposit of Shanghai based on the aforementioned procedure.
• The effective insertion depth of a retaining wall to blocking seepage for the soil of Shanghai was obtained.

In the design of a deep retaining wall, it is necessary to consider the blocking effect on groundwater seepage of retaining walls in aquifers. In this study, both laboratory tests and numerical simulation with finite element method (FEM) were adopted to investigate the blocking effect on groundwater seepage under different insertion depths of retaining wall in aquifer. Laboratory tests were conducted to analyze this blocking effect in an unconfined aquifer. The test results indicate that the effective insertion depth ratio (J) of a retaining wall in Shanghai aquifer sand is about 70%. A three-dimensional numerical model (3D-FEM) was conducted to analyze the laboratory test results. The FEM results show that FEM is a reliable method to analyze the blocking effect on groundwater seepage in an aquifer. Based on the same aforementioned procedure, a 3D FEM model is established to investigate the blocking effect in the confined aquifer in Shanghai deposit. Both laboratory test and FEM results show that drawdown of groundwater level decreases with an increase of the insertion depth ratio, J, of retaining structures in an aquifer. The optimal value of J (approximately 70%) is achieved for retaining wall based on the synthetic results from laboratory test, FEM analysis, and the equation of Pujades et al. for either unconfined aquifers or confined aquifers of Shanghai.