Geosynthetic Encased Column: comparison between numerical and experimental results

The use of granular column is one of the ground improvement methods used for soft soils. This method improves the foundation soils mechanical properties by displacing the soft soil with the compacted granular columns. The columns have high permeability that can accelerate the excess pore water pressure produced in soft soils and increase the undrained shear strength. When it comes to very soft soils, the use of granular columns is not of interest since these soils present no significant confinement to the columns. Here comes the encased columns that receive the confinement from the encasement materials. In this study, the influence of the column installation method on the surrounding soil and the encasement effect on the granular column performance were investigated using numerical analyses and experimental tests. The results show that numerical simulations can reasonably predict the behavior of both the encased column and the surrounding soil.

Numerical Simulation of Granular Column Collapse with Fractal Particle Size Distribution Using Discrete Element Method

This study conducts numerical simulations of the granular column collapse with Fractal Particle Size Distributions (FPSDs) via the Discrete Element Method (DEM) and investigated kinetic behaviours of dry granular flows. The aim of this paper is to explore the effects of the fractal dimension of FPSD on the kinetics of dry granular flows. When the fractal dimension of the flows consisting of granular materials increases, the horizontal particle translational velocities become greater and the mobility improves, whereas the particle rotational velocities decrease. Meanwhile, the change in the potential energy increases, and the particle kinetic energy in the rotational form reduces; thus, the particle kinetic energy in the translational form increases. The reducing particle rotational movement may be related to the reducing particle shearing behaviours because only the contact shearing can affect particle rotational motion. In conclusion, a larger fractal dimension of FPSD of a dry granular flow leads to a longer spreading distance and a smaller rotational velocity.

From laboratory experiments to geophysical tsunamis generated by subaerial landslides

Modeling of tsunami waves generated by subaerial landslides is important to provide accurate hazard and risk assessments in coastal areas. We perform small-scale laboratory experiments where a tsunami-like wave is generated by the gravity-driven collapse of a subaerial granular column into water. We show that the maximal amplitude reached near-shore by the generated wave in our experiments is linked to the instantaneous immersed volume of grains and to the ultimate immersed deposit. Despite the differences in scale and geometry between our small-scale experiments and the larger-scale geophysical events, a rather good agreement is found between the experimental law and the field data. This approach offers an easy way to estimate the amplitude of paleo-tsunamis.