Electrical resistivity method for water content and compaction evaluation, a laboratory test on construction material

The amount of water content (WC) and the density of geotechnical parameters are important because it affects various engineering structures. In the geotechnical test, there is an increased need for the development of efficient methods for measuring the soil WC and the density of structural materials in the construction. These soil parameters are measured by destructive and non-destructive methods. In general, destructive methods are time-consuming and provide limited information, while electrical resistivity (ER) method is a fast, non-invasive and inexpensive method that has a high capability to predict geotechnical parameters such as WC and compaction. Laboratory ER tests on construction materials with different compaction and WC were conducted in this research. The purpose of this exercise was to develop a methodology based on the amount of soil ER in order to formulate a correlation between the amount of gravimetric water content (GWC) and soil compaction as well as the interaction relation between these parameters. The tested soil was GW-GM type and A-1-a type according to USCS and AASHTO respectively (Soil type E base material according to Iranian highway specifications code) and non-plastic. Data analysis shows a linear relationship between ER and compaction and a third degree polynomial relationship between ER and GWC. In addition, the obtained relationships indicate that the third degree polynomial curve fitted on the ER-GWC data (R-square: 0.8716) is more appropriate than the fitted curve on the ER-degree of saturation data (R-square: 0.7471). To find the interactive relationship between the parameters, robust linear least-squares (bisquare) method was used. Finally, a polynomial relationship between ER-GWC-Compaction is established with R-square 0.9142 and RMSE 12.16. The proposed relationship is also compared with Archie's law.