Détermination du coefficient des terres au repos (K0) à l’aide d’un pressiomètre innovant

Abstract

Knowledge of the coefficient of lateral earth pressure at rest (K0) obtained through in situ measurements is highly valuable for the geotechnical modeling of structures. Indeed, this parameter plays a crucial role in evaluating slope stability, lateral earth pressures on retaining structures, as well as heave phenomena during excavation works. However, its determination remains challenging, even with testing methods specifically developed for this purpose. The K0 coefficient can be measured using the self-boring pressuremeter (SBPMT), which minimizes soil disturbance during installation. Nevertheless, this technique remains costly and complex to implement. Methods employing displacement-based devices installed by driving or pushing such as the Marchetti flat dilatometer (DMT), the K0 stepped blade, or the push-in pressure cell generally lead to an overestimation of K0 due to the induced soil disturbance. Consequently, the full-displacement pressuremeter (FDPMT), characterized by high soil displacement, is not recommended for this type of measurement. This master’s thesis partakes in the ongoing efforts aimed at determining the coefficient of earth pressure at rest K0 in a simple, reproducible, more accurate, and cost-effective manner. This work includes a literature review dedicated to the determination of K0 using in situ methods, laboratory tests, and empirical correlations. Furthermore, this research presents an innovative pressuremeter device designed to overcome certain limitations of conventional Ménard pressuremeters and to enhance the quality of measurements obtained during testing. An experimental field campaign was carried out at a study site located in Tlemcen using this new pressuremeter equipment. Comparisons with conventional Ménard pressuremeter tests were performed on in situ soils at depths ranging from 1 to 15 meters. The results obtained with the new pressuremeter demonstrate that it is possible to determine the initial in situ horizontal stress h0 and, consequently, the coefficient of earth pressure at rest K0 in a simple and accurate manner. The proposed device, combined with a specific loading program, constitutes a promising alternative for measuring initial stress states in soils.