A unit series–parallel unsaturated soil electrical conductivity model considering interconnections between pores

Abstract

For the potential application of electrical resistivity measurements in hydrogeological investigations, the knowledge of soil electrical conductivity mechanism with moisture content variation is the key issue. The impact of interconnections between pores and weak connection to physical processes were the two limitations for unsaturated soil electrical conductivity research. In this work, we introduced the concept of equivalent conductive pathway to analyze tortuosity. Based on media series–parallel analysis, a unit series–parallel unsaturated soil electrical conductivity model considering interconnections between pores was established, in which parameters with its own physical meaning. To verify the accuracy of the proposed model, soil resistivity test with moisture content variation was conducted. Soil electrical conductivity was predicted, which was compared with results from test and previous models. The results indicate that our model is expected to produce better results than the previous models. Overcoming the limitations of weak connection to physical processes in the empirical model, the error of soil resistivity was significantly reduced when the impact of interconnections between pores was considered. The average error of the proposed model for clay and sand was 30.6% and 17.4%, respectively, compared to 72.6% and 48.2% for the model that ignored the interconnections between pores. The findings of this study could provide a reference for hydrogeological investigations, such as levee leakage detection.