Mesure de la déformabilité des sols in situ à l'aide d'un essai de chargement statique d'une pointe pénétrométrique

Abstract

The penetrometers allow one to obtain a global parameter, which is the cone resistance; this one is related to the soil failure and not to its deformability. The idea is to use a penetrometer to measure in situ the deformability properties of the soils. A new method of soil deformability measurement is then presented in this article: a monotonic static loading test using a penetrometer. The main objective is to measure particularly the three mechanical parameters, which are Young's modulus E, the cohesion c, and the friction angle ϕ. This article describes the testing equipment and the tests performed by precise procedure. An interpretation of the obtained monotonic experimental curves is also presented. It is based on a mathematical regression by three coefficients. According to this study, conducted on a purely frictional soil, the test allows one to obtain by a simple, fast, and economic way, a relevant evaluation of the soil deformability properties and its resistance. An axisymmetric finite element model of the experimental test is proposed to identify the correlation between the three mathematical coefficients of the experimental curve and the three rheological parameters E, c, and ϕ. The initial conditions before the test, which are crucial, are simulated by performing an unloading–reloading loop. Interesting results are obtained with this simplified, but realistic, finite element model. However, a simulation considering large strain conditions is still needed.Key words: penetrometer, deformability, monotonic static loading, deformation modulus, finite element simulation.