Seepage visualization and detection of diaphragm wall leakage with electrical potential method: an experimental investigation

Attributed to the opacity of soil and rock mass, seepage visualization is a thorny problem in the model test around diaphragm wall leakage, which has played an increasingly significant role in deep excavation engineering recently. Enlightened by the geoelectrical field response method, the electrical potential method was proposed in this study. By means of a model experiment, the applicability of the proposed method was verified and approaches for evaluating the seepage characteristics were discussed. Based on the analyses, several conclusions could be drawn: (i) based on the electrical potential method, a circuit is established by connecting the power supplier, the ground and several monitoring electrodes and voltmeters. When the seepage passes through a certain electrode, the increase of voltage can be observed so that the seepage flow can be visualized. (ii) The effectiveness of the electrical potential method is validated by the excellent agreement between photos of practical seepage flow and the nephograms depicted on the basis of the voltages measured on the electrodes. (iii) The time history curve of the measured voltage is S-shaped and composed of a small ladder rising stage, a sharp increasing stage and a convergence stage. The seepage flow velocity, inhomogeneity and the leakage point location can be evaluated by the time cost between the two major rise beginning points, the time cost for the major rise process and the maximum measured voltage, respectively. The proposed method can provide valuable support to the diaphragm wall leakage model test and other seepage experiments.