Analysis of uplift pressure anomaly of Lijiaxia Dam foundation

With regard to the uplift anomaly phenomenon occurred in the right abutment of Lijiaxia Dam in China,a three-dimensional finite element model for seepage of the dam and its foundation was established.The methods of modeling the seepage prevention curtains were introduced.The drainage holes were modeled as so-called drainage sub-structures.Then an approach of back analysis for seepage parameters based on artificial neural network was proposed.The back analysis was conducted and the permeability tensors of the rock masses were obtained.The three-dimensional finite element analysis of seepage flow through the dam and its foundation was performed.Using the analytic results the influence of various factors such as seepage prevention measures,drainage and geologic conditions in the seepage field was evaluated,and then the cause of uplift anomaly was investigated combined with the results of the drilling and water quality tests in the foundation.It was shown that anomaly phenomenon was due to the grout curtain defects and leakage channel exiting in the shallow foundation.