Laboratory-Scale Free Fall Cone Penetrometer Test on Marine Clay: A Numerical Investigation Using the Generalized Interpolation Material Point Method

Abstract

This paper presents a series of laboratory free-fall cone penetrometer (FFCP) tests conducted on marine clay samples collected from the Gulf of Finland in the Baltic Sea. Subsequently, these tests are replicated numerically with the generalized interpolation material point method (GIMP) simulations. First, the paper gives laboratory-scale FFCP experiment results used for the validation of the numerical framework. In these experiments, a small-scale model of a FFCP was dropped from various heights into a natural marine clay soil sample and recorded using a high-speed camera. The tests were supplemented with a laboratory test program to determine the geotechnical properties of the clay used in the experiments. Following image processing, the tests provided data for numerical simulations: displacement, velocity, acceleration, and reaction force curves associated with the FFCP during the penetration process. The GIMP simulations shown in the paper replicate the process of penetration of the FFCP into the marine clay. The simulations used a strain-rate dependent Tresca constitutive model, extended with strain softening that replicates the reduction of the undrained shear strength due to destructuration, an important feature of the material. The numerical simulations replicate the experiments well. The study examines the effect of cone penetrometer roughness, impact velocity, mesh density, strain rate, and strain softening on the cone penetrometer penetration process. The simulation results indicate that the presented framework can replicate the dynamic penetration process on soft and sensitive clay very well.