Abstract:  To enhance the accuracy of high-density electrical resistivity methods in the investigation of reservoir embankments and eliminate the influence of their trapezoidal geometry, a three-dimensional forward modeling approach based on a hybrid finite element-infinite element method with unstructured meshes was employed. Numerical simulations were conducted on a representative embankment model, incorporating variations in geometric structure, electrode array configurations, and survey line positions. The results indicate that the trapezoidal structure of reservoir embankments exerts a significant influence on high-density electrical methods, particularly on the apparent resistivity at the deeper sections, often causing overestimation of apparent resistivity at depth. All tested array configurations exhibits this effect, and the closer the survey line is to the crest of the embankment, the stronger the impact of the trapezoidal structure. To address this issue, a correction method based on apparent resistivity ratio was proposed. Both theoretical model numerical simulation results and field data experimental results confirm that this correction effectively eliminates the artificial deep high-resistivity anomalies induced by the trapezoidal structure. The corrected inversion results no longer exhibit pseudo-layering effects associated with embankment geometry, thereby improving the reliability of both forward and inverse modeling outcomes.

Key words: high-density electrical method, ratio method, numerical simulation, dam detection, finite element-infinite element, unstructured mesh