Francesca Ceccato

Analysis of Piezocone Penetration under Different Drainage Conditions with the Two-Phase Material Point Method

AbstractThe piezocone penetration test (CPTU) is commonly used to identify a soil’s profile and estimate its material properties. Depending on the soil type, ranging from clay to sand, undrained, partially drained, or drained conditions may occur during cone penetration. In silt and sand–clay mixtures, the CPTU penetration is characterized by partially drained conditions, which are often neglected in data interpretation. The effect of drainage on CPTU measurements has been mainly studied experimentally. Numerical analyses are rare because taking into account large soil deformations, soil–water and soil–structure interactions, and nonlinear soil behavior is still a challenging task. This paper presents and discusses numerical simulations of CPTU in saturated soils with the two-phase material point method. Soil behavior is described with the modified cam clay model. This study investigates the effects of pore pressure dissipation during penetration, cone roughness, and horizontal stress state, comparing the...

The effect of the front inclination on the impact forces transmitted by granular flows to rigid structures

Open image in new window The assessment of the damage of existing structures caused by flow landslides, as well as the design of sheltering structures, requires the evaluation of the forces arising during the impact. In particular, the peak force depends on several factors such as the impact velocity, the material bulk density, the flow thickness, and the material compressibility. The effect of the front shape on the force evolution has rarely been taken into account because it is experimentally very difficult to consider. The aim of this paper is to study numerically the impact process evaluating the effect of the material constitutive parameters and shape of the flow front. Large deformations of the granular material are simulated by employing a 3D numerical approach based on the Material Point Method (MPM). The granular material mechanical behavior is simulated by means of an elastic perfectly plastic model with a Mohr-Coulomb failure criterion. The soil mass is initially positioned in front of the wall with a prescribed uniform velocity and the evolution of the impact force is monitored. The results show that the front shape not only influences the peak pressure, but also the evolution of the impact force with time.

Effect on the Structure in Elevation of Wood Deterioration on Small-Pile Foundation: Numerical Analyses

ABSTRACT Wooden pile foundations are quite common in Venice historical building. Very short, small-diameter piles are embedded into the soft shallowest soil layer under the groundwater level, but wood degradation is not prevented as anaerobic bacteria can flourish even in anoxic condition. This study couples the behavior of the masonry structure and the foundation as result of pile degradation. The numerical analyses, relative to the ancient piling, consider wood decay and secondary settlement of soil. The effect of deterioration as a function of the pile spacing and the possible presence of a stiff layer under pile tips are also investigated. The geotechnical results are then used as input for the structural model. The behavior of the masonry as result of different states of wood conservation along the wall is studied numerically.

MPM Simulations of the Impact of Fast Landslides on Retaining Dams

Possible protection systems against flow-like landslides are earth dams built to stop or deviate the flow. The evaluation of impact forces on the structures is still based on oversimplified empirical approaches, which may lead to a very conservative design, with high costs and environmental impact. Numerical methods able to capture the essential features of the phenomenon can offer a valuable tool to support the design of protection measures. This paper shows the potentialities of the Material Point Method (MPM) in this field. A dry granular flow, modelled with the Mohr-Coulomb model is considered. The landslide is placed in front of the barrier with a prescribed velocity and the impact forces on the slanted face is monitored with time.