Joint imaging of ERT datasets and its application in seepage characterization at Nanshan Dam, southeast China

Abstract

Estimating resistivity distributions within dam structures accurately using electrical resistivity tomography (ERT) poses a significant challenge due to the limited 2D acquisition scheme, the 3D heterogeneity of near-surface materials, and the dynamic nature of fluid transport. To address this challenge, we present a new strategy by simultaneously inverting multiple collinear ERT datasets acquired from various standard electrode arrays. This strategy incorporates the coupling of the intrinsic parameter relationship into the objective function, constraining the inversion solution space by balancing the distinct resolution characteristics associated with the electrode arrays involved in the joint inversion process. Using synthetic Karst and infiltration models, we demonstrate that our strategy can yield accurate inversion results for both the Wenner and dipole-dipole datasets. Application of this strategy to a field case at Nanshan Dam in southeast China, which involves Wenner, Wenner-Schlumberger, and dipole-dipole surveys, successfully delineates preferential fluid seepage pathways. These findings are further corroborated by consistent inferred reflectors in Ground Penetrating Radar (GPR) profiles. The synthetic and field examples highlight the effectiveness of our strategy in achieving accurate and unified resistivity estimates by integrating multiple ERT datasets.