Browsing by Author "Yerro, Alba"

Now showing 1 - 4 of 4
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    Constitutive modelling of non-cohesive soils under high-strain rates: a consistency approach
    Zambrano-Cruzatty, Luis E.; Yerro, Alba; Macedo, Jorge (ICE Publishing, 2022-08)
    Rapid loading of sands is a common issue in geotechnical engineering problems such as projectile or free-fall impact. At high strain rates (HSR), soils show more strength and enhanced dilation (viscoplastic behaviour) compared to the response at low rates (inviscid behaviour). However, few constitutive models account for the viscoplasticity of sands. Hence, the development of viscoplastic models is highly desired. Usually, viscoplasticity is modelled using overstress methods. However, overstress methods impose an overall modification of the constitutive equations, which prevents control of the evolution of internal state variables and the enforcement of the consistency condition. In this study, a generalised consistency-viscoplasticity method is proposed and applied to a non-associative modified Mohr-Coulomb model with coupled stress-dilation relation. The influence of strain rate is incorporated using a work-energy approach by way of an inertial coefficient. Two explicit integration strategies are proposed and compared, and guidelines for their implementation are shared. The numerical response of the model is tested by using drained triaxial simulations under constant axial strain rate, relaxation and impact loading. The results indicate that the consistency-viscoplasticity is a feasible alternative to simulate soil behaviour under HSR, capturing reasonably well the observed experimental responses.
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    Failure mechanism, existing constitutive models and numerical modeling of landslides in sensitive clay: a review
    Urmi, Zinan A.; Saeidi, Ali; Chavali, Rama V. P.; Yerro, Alba (2023-05-26)
    Landslides involving sensitive clays are recurrent events in the world's northern regions and are especially notorious in eastern Canada. The two critical factors that separate sensitive clay landslides from traditional slope stability analysis are the highly brittle behavior in undrained conditions (strain-softening) characteristic of progressive or retrogressive failures and the large deformations associated with them. Conventional limit equilibrium analysis has numerous shortcomings in incorporating these characteristics when assessing landslides in sensitive clays. This paper presents an extensive literature review of the failure mechanics characteristics of landslides in sensitive clays and the existing constitutive models and numerical tools to analyze such slopes' stability and post-failure behavior. The advantages and shortcomings of the different techniques to incorporate strain-softening and large deformation in the numerical modeling of sensitive clay landslides are assessed. The literature review depicts that elastoviscoplastic soil models with non-linear strain-softening laws and rate effects represent the material behavior of sensitive clays. Though several numerical models have been proposed to analyze post-failure runouts, the amount of work performed in line with sensitive clay landslides is very scarce. That creates an urgent need to apply and further develop advanced numerical tools for better understanding and predicting these catastrophic events.
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    Numerical simulation of a free fall penetrometer deployment using the material point method
    Zambrano-Cruzatty, Luis; Yerro, Alba (2020-06)
    Free Fall Penetrometer (FFP) testing consist of a torpedo-shaped body freefalling into a soil target. The use of this type of device is becoming popular for the characterization of shallow sediments in near-shore and off-shore environments because it is a fast, versatile, and non-expensive test capable of recording acceleration and pore pressures. In recent years, the data analysis advanced considerably, but the soil behavior during fast penetration is still uncertain. Hence, there is a need to develop numerical models capable of simulating this process to improve its understanding. This paper proposes a numerical framework to simulate the deployment of an FFP device in dry sands using the Material Point Method (MPM). A moving mesh technique is used to ensure the accurate geometry of the FFP device throughout the calculation, and the soil-FFP interaction is modelled with a frictional contact algorithm. Moreover, a rigid body algorithm is proposed to model the FFP device, which enhances the performance of the computation and reduces its computational cost. The sand is simulated by using two constitutive models, a non-associate Mohr-Coulomb (MC) and a Strain-Softening Mohr-Coulomb (SSMC) that reduces, exponentially, the strength parameters with the accumulated plastic deviatoric deformation (Yerro et al., 2016) Variable dilatancy, which reduces as a function of the plastic strain, is also taken into account, and the strain-rate effects have been evaluated in terms of peak friction angle. In general, the behavior predicted by the MPM simulations is consistent with the experimental test. The results indicate that the soil stiffness has a big impact on the deceleration time-history and the development of a failure mechanism, but less influence on the magnitude of the peak deceleration and the penetration depth; the soil dilatancy reduces the FFP rebound, and the FFP-soil contact friction angle and the peak friction angle are highly linked to the peak deceleration. (C) 2020 Production and hosting by Elsevier B.V. on behalf of The Japanese Geotechnical Society.
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    Soil-Water-Structure Interactions
    Yerro, Alba; Ceccato, Francesca (MDPI, 2023-05-05)
    Interactions between soil, fluids (e.g., water), and structures are intrinsic to most geotechnical problems. However, these can be extremely complex and further understanding is needed in this field. Soil–water–structure interactions can be studied on many different scales (micro to macro) and perspectives (experimental, numerical, and theoretical). In any case, the consequences of these interactions control soil behaviour, the stability of civil infrastructure, and, ultimately, the safety of our communities. This Special Issue consists of five papers (three research papers and two literature reviews) that highlight the importance of soil–water–structure interactions in a broad range of different applications. The topics addressed in the research contributions include (a) the performance of shallow footings under oblique loads, (b) the assessment of nonlinear base-isolated building systems under dynamic loading, and (c) the applicability of lightweight materials as fill for retaining wall systems. The other innovative papers, on the other hand, provide comprehensive reviews on (d) the role of the clay content in the interface characteristics between sand–clay mixtures and structures and (e) the latest developments in the understanding and measurements of the Atterberg limits.