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A series of plate loading tests on clay has been conducted in the centrifuge. The aim of the tests is to create a data set, which is freely downloadable, to validate numerical tools that account for geometrical nonlinearities. The tests include two sources of geometrical non-linearities. The first source is the reducing clay layer thickness below the plate, which causes an increase in resistance. The second source is the backflow of the clay around the tip of the plate. The backflow has a reducing effect on the plate resistance. This paper outlines four tests: two involving a wide plate and two with a small plate. Each plate geometry is investigated under both smooth and rough side model boundaries. An material point method (MPM) schematization is used for numerical analysis. The schematization and parameter selection are initially validated by comparing the MPM results against CPTu data in each test. The numerical analysis examines the impact of a finite layer thickness by analyzing various layer thicknesses. Furthermore, the analysis shows the influence of the backflow on the plate resistance by analyzing different ratios of shaft to plate width. In this study, the pore pressures below the plate and vertical and horizontal displacement fields are considered in addition to the load displacement curves. The MPM simulations are in good agreement with the centrifuge data. [ABSTRACT FROM AUTHOR]

The study on impact mechanisms of flow-like landslides against structures is still an open issue in the scientific literature. Many researchers have so far employed either experiments or numerical methods, but the evaluation of the impact forces on mitigation obstacles remains difficult especially if the solid- fluid interaction within the flow is considered. This study shows how advanced numerical tools, such as material point method, may be used in simulating those complex processes. The simulations are carried out for two well-documented laboratory tests: a dry granular flow impacting a rigid wall under different geometries and testing conditions in a small-scaled flume and a saturated flow with complex propagation pattern in a centrifuge apparatus. The numerical modelling is validated against the observations and then used to explore the response of different flows impacting rigid structures in other conditions than in the experiments. The soil-fluid interaction influences the type of impact mechanism, the kinematics of the flow, and the space-time trend of the impact pressure against the structure. Key words: mechanism, numerical, material point method, impact. La litterature scientifique ne s'est pas encore prononcee sur l'etude des mecanismes d'impact des glissements de terrain contre les structures. Un grand nombre de chercheurs ont employe a ce jour soit des experiences, soit des methodes numeriques, par contre l'evaluation des forces d'impact sur les obstacles d'attenuation reste difficile, surtout si l'on considere l'interaction solide-fluide au sein du flux. La presente analyse demontre la maniere dont des outils numeriques avances, tels que la methode des points materiels, se pretent a la simulation de ces processus complexes. On a effectue les simulations pour deux essais de laboratoire bien documentes : un flux granulaire sec impactant une paroi rigide dans des conditions d'essai et des geometries differentes dans un canal a petite echelle et un flux sature avec un modele de propagation complexe dans un appareil de centrifugation. Une fois validee par rapport aux observations, la modelisation numerique est utilisee pour explorer la reponse de differents flux impactant des structures rigides dans d'autres conditions que celles des experiences. Chaque interaction sol-fluide influence le type de mecanisme d'impact, la cinematique du flux et la tendance spatio-temporelle de la pression d'impact contre la structure. [Traduit par la Redaction] Mots-cles: mecanisme, numerique, methode des points materiels, impact., 1. Introduction Flow-like landslides are dangerous for people and structures around the world (Pastor et al. 2009), due to the long travel distances up to tens of kilometres and the [...]

Pile installation leads to significant changes in soil state (i.e., void ratio and effective stress) around the pile, which affects stiffness and bearing capacity. Currently, the driveability of piles is analyzed using empirical methods, and the ultimate bearing capacity is estimated without considering the installation effects. This paper presents simulations of the entire installation and subsequent axial bearing capacity of a close-ended pile using a single numerical tool based on the material point method (MPM). A lab-scale experiment is used as a validation case, where the pile is first impact-driven in dry sand, with different initial relative densities (from loose to very dense), and then axially loaded. A state-dependent constitutive model (DeltaSand) is used in the numerical simulations to predict the mechanical behavior of the sand at different relative densities with a single set of input parameters. The paper also illustrates several enhancements needed to obtain more accurate results: (1) an improved contact algorithm that allows gap closure; (2) a rigid-body formulation for the pile body; and (3) a general analytical solution for calculation of energy-consistent impact forces in uncoupled hammer-pile systems. [ABSTRACT FROM AUTHOR]