Geotechnical and electrical properties of sensitive clay in Saint-François-de-la-Rivière-du-Sud, Québec, Canada

ABSTRACT: Several flowslide scars are found in a deposit of clay along the banks of the du Sud River in the area of Saint-François-de-la-Rivière-du-Sud located near Montmagny, Québec, Canada. In collaboration with the Ministère des Transports, de la Mobilité durable et de l’Électrification des transports du Québec and Université Laval, a geotechnical and geophysical investigation was undertaken to characterize the geotechnical and electrical properties of this clay deposit and assess the suitability of measuring electrical resistivity to map the areas prone to large retrogressive landslides. An electrical resistivity tomography was carried out along a survey line of 1435 m in length. A total of seven cone penetration tests with pore water pressure measurements and one electrical resistivity measurements were performed along this survey line. Basic geotechnical tests were also performed on samples obtained from three boreholes located close to three cone penetration tests. Based on the results, the studied clay deposit is made of four distinctive layers of clay and correlations have been found between their geotechnical properties, salinity and electrical resistivity.