Working behaviour feedback of composite geomembranes based on seepage monitoring data

To assess the durability of the impermeability of composite geomembranes in hydraulic engineering projects, using nearly 20 years (2000–2018) of seepage monitoring data from the Wangfuzhou Hydraulic Engineering Project, this study conducts feedback analysis on the anti-seepage performance of the composite geomembranes of this project. Firstly, based on the seepage monitoring data, a qualitative analysis of the overall seepage behaviour of the embankment dams was carried out. Then, a typical section of the embankment dams was selected for quantitative analysis by establishing a statistical model of the water levels in piezometric pipes. Subsequently, orthogonal design, a neural network and a numerical calculation method were combined to invert the permeability coefficient of the composite geomembranes. Lastly, the working behaviour of the composite geomembranes was comprehensively analysed. The results show that the measured water level and separated time-dependent components of three piezometric pipes in the typical section GY5 decreased gradually during the study period. The permeability coefficient of the composite geomembranes inverted using the measured water level was 1.11 × 10^–12 m/s. It is concluded that, after nearly 20 years of service, the composite geomembranes of the Wangfuzhou Hydraulic Engineering Project have experienced no apparent deterioration trend over time.