CBR Mapping Prediction from 2D Resistivity Imaging Using Regression Following Archie’s Formula

Abstract

Indirect geophysical methods are increasingly associated with direct underground methods ininvestigating the subsurface to address environmental and geotechnical problems and reducethe cost of underground studies. These methods make it possible to explore large areas withacceptable precision, time, and cost. The present study combines the electrical resistivitymethod with the California Bearing Ratio for exploring an area located west of theNouakchott port in Mauritania. The study aims firstly to verify that the thickness of thebackfill layer must be less than 2 m throughout the entire study area and secondly to mapareas with low California Bearing Ratio values (<80%) indicating substandard backfillcompaction using 2D Electrical Resistivity Tomography imaging survey and regression. Themeasured Electrical Resistivity values exhibit a good nonlinear regression with CaliforniaBearing Ratio, following Archie's equation. A map of California Bearing Ratio variation wasderived from the Electrical Resistivity values, indicating the distribution and variation of soilstrength in the study area. The results revealed that the backfill layer did not meet thestandards, with approximately 35% of the total area having a California Bearing Ratio valuebelow 80%. The areas with poor compaction requiring treatment were primarily located inthe southern sector, followed by the middle and eastern sectors.