A numerical model for nonlinear large deformation dynamic analysis of unsaturated porous media including hydraulic hysteresis

Shahbodagh, Babak; Khalili, Nasser; Esgandani, Golnaz Alipour

doi:10.1016/j.compgeo.2015.06.008

Cited by 42 publications

(24 citation statements)

References 47 publications

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“…The effect of considering the hydraulic hysteresis on the results of one dimensional consolidation of unsaturated elastic porous media is studied in this section. A one‐dimensional consolidation problem whose FEM solution is available is adopted for this purpose. The problem involves a 100‐m‐long unsaturated soil column as illustrated in Figure .…”

Section: Numerical Examplesmentioning

confidence: 99%

“…The material properties adopted are summarised in Table . A fluid phase with hypothetical mechanical properties is considered in this example, according to Shahbodagh‐khan et al Also, in order to be consistent with the reference FEM solution, Equation is replaced by an empirical equation proposed by Taylor for updating the intrinsic permeability of the medium with void ratio, as follows:

k = k_{0} exp ((), \frac{e - e_{0}}{C_{k}}),

where C k is a material parameter taken as 1.0 in this example.…”

Section: Numerical Examplesmentioning

confidence: 99%

“…The majority of the numerical models developed for simulation of flow and deformation in unsaturated porous media are in the framework of the finite element method (FEM) . Another class of numerical methods, referred to as meshfree methods (MMs), has gained popularity, particularly during the past two decades, since they overcome some intrinsic difficulties of the FEM .…”

Section: Introductionmentioning

confidence: 99%

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Fully coupled elastoplastic hydro‐mechanical analysis of unsaturated porous media using a meshfree method

Ghaffaripour

Esgandani

Khoshghalb

et al. 2019

Num Anal Meth Geomechanics

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Summary This paper presents the first application of an advanced meshfree method, ie, the edge‐based smoothed point interpolation method (ESPIM), in simulation of the coupled hydro‐mechanical behaviour of unsaturated porous media. In the proposed technique, the problem domain is spatially discretised using a triangular background mesh, and the polynomial point interpolation method combined with a simple node selection scheme is adopted for creating nodal shape functions. Smoothing domains are formed on top of the background mesh, and a constant smoothed strain, created by applying the smoothing operation over the smoothing domains, is assigned to each smoothing domain. The deformation and flow models are developed based on the equilibrium equation of the mixture, and linear momentum and mass balance equations of the fluid phases, respectively. The effective stress approach is followed to account for the coupling between the flow and deformation models. Further coupling among the phases is captured through a hysteretic soil water retention model that evolves with changes in void ratio. An advanced elastoplastic constitutive model within the context of the bounding surface plasticity theory is employed for predicting the nonlinear behaviour of soil skeleton. Time discretisation is performed by adopting a three‐point discretisation method with growing time steps to avoid temporal instabilities. A modified Newton‐Raphson framework is designed for dealing with nonlinearities of the discretised system of equations. The performance of the numerical model is examined through a number of numerical examples. The state‐of‐the‐art computational scheme developed is useful for simulation of geotechnical engineering problems involving unsaturated soils.

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Section: Numerical Examplesmentioning

confidence: 99%

k = k_{0} exp ((), \frac{e - e_{0}}{C_{k}}),

where C k is a material parameter taken as 1.0 in this example.…”

Section: Numerical Examplesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Fully coupled elastoplastic hydro‐mechanical analysis of unsaturated porous media using a meshfree method

Ghaffaripour

Esgandani

Khoshghalb

et al. 2019

Num Anal Meth Geomechanics

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“…For instance, Muraleetharan and Wei and Ravichandran and Muraleetharan developed the governing equations for the seismic behavior of unsaturated soils and used a two stress state approach [3,4]. Whereas, Uzuoka and Borja (2012), ShahbodaghKhan et al (2015), and Ghorbani et al (2016) have used the effective stress approach and single stress framework [5][6][7]. It has been stated that single stress approach can eliminate the need for multiple constitutive parameters for nonlinear response of unsaturated soils.…”

Section: Introductionmentioning

confidence: 99%

“…Zienkiewicz et al (1990) were first to study the dynamic behavior of unsaturated soils [2]. Their pioneering work has been followed by a couple of other studies in which different aspects of the unsaturated soils' response to the seismic excitations have been investigated [3][4][5][6][7]. Different constitutive equations and assumptions in these studies have been considered.…”

Section: Introductionmentioning

confidence: 99%

Seismic response of earth dams considering dynamic properties of unsaturated zone

2016

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Abstract. It is conventionally assumed in the analysis and design of earth dams that the soil located above the phreatic line, i.e. the uppermost seepage flow line, is completely dry. However, there is often an unsaturated flow of water through an unsaturated zone above this borderline and variation in moisture content in this zone results in variation of matric suction throughout this region. Variation of matric suction, in turn, results in variation of effective stresses in this zone. In this research, the seismic response of earth dams in terms of the displacement and acceleration at the crown of the dam as well as the stress distribution in the dam body is investigated. Taking into account the effect of unsaturated zone, a comparison is made to investigate the effect of conventional simplification in ignoring the dynamic characteristics of the unsaturated zone above the phreatic line and the more complicated analysis which includes the unsaturated zone. A function for the soil-water retention curve (SWRC) was assigned to the soil in the unsaturated zone to determine the variation of matric suction in this zone and analyses were made using finite difference software (FLAC). Results are then compared to the conventional method for homogeneous dams. In these analyzes the soil shear modulus was assumed to vary with the mean effective stress both for saturated and unsaturated zones. Among various results, it was notable that the history of crest x-displacement, and acceleration show higher values in models accounting for the unsaturated region. It was attributed to the considerably lower values of damping ratio in the crest region in the unsaturated models.

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A computational model for dynamic strain localization in unsaturated elasto‐viscoplastic soils

Oka

Shahbodagh

Kimoto

2018

Num Anal Meth Geomechanics

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Summary Strain localization has been the subject of extensive theoretical and numerical studies over the last four decades. The static and dynamic strain localization in both dry and water‐saturated geomaterials has widely been investigated numerically. However, studies on unsaturated geomaterials have been insufficient. This paper presents a computational model for nonlinear dynamic analysis of strain localization in multiphase geomaterials. The discretization of the governing equations is achieved using the finite element method in the finite deformation regime with the updated Lagrangian description. An elasto‐viscoplastic model extended to include the effect of suction on the behavior of partially saturated clay is used in the formulation. The nonlinear kinematic hardening rule and softening due to the structural degradation of soil particles are taken into account in the model. The inception and progression of localization in fully saturated and unsaturated clay under dynamic compressive loading are investigated. In the unsaturated case, the strain localization becomes more pronounced and much clearer shear bands are formed. More brittleness is observed in the unsaturated case due to the collapse of suction force caused by shearing. This demonstrates that even though suction improves the mechanical properties of soil, ie, increasing the stiffness and shear strength, the hypothesis of fully saturation is not at all on the side of safety due to the drastic loss of strength associated with the collapse of suction which may cause a strong strain localization.

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A numerical model for nonlinear large deformation dynamic analysis of unsaturated porous media including hydraulic hysteresis

Cited by 42 publications

References 47 publications

Fully coupled elastoplastic hydro‐mechanical analysis of unsaturated porous media using a meshfree method

Fully coupled elastoplastic hydro‐mechanical analysis of unsaturated porous media using a meshfree method

Seismic response of earth dams considering dynamic properties of unsaturated zone

A computational model for dynamic strain localization in unsaturated elasto‐viscoplastic soils

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