Papers by Behrouz Gatmiri
In this paper, an advanced formulation of time-domain two-dimensional Boundary Element Method (BE... more In this paper, an advanced formulation of time-domain two-dimensional Boundary Element Method (BEM) for linear elastodynamics is used to carry out site response analysis of topographic structures subjected to incident P-, SV-, and Rayleigh waves. A modified set of well behaved full space two-dimensional elastodynamic convoluted kernels is presented and employed, that has a higher degree of accuracy than those
ABSTRACT In the THM modeling of multiphase medium, the coupling effects of skeleton, suction, and... more ABSTRACT In the THM modeling of multiphase medium, the coupling effects of skeleton, suction, and temperature have been integrated via the concept of state surfaces of void ratio and degree of saturation. Based on proposed formulation, a fully coupled numerical model for the behavior of soil deformation, water flow, air flow, heat flow in unsaturated soil has been developed and integrated in a finite element code θ-Stock by the first author. This program is conceived with this idea that it will be able to analyze the response of a soil in different states of humidity to mechanical, thermal loading, and also damage phenomena. Damage model is dedicated to unsaturated brittle rocks. It mixes phenomenological and micromechanical concepts and is formulated based on the use of independent state variables. The expression of the liquid permeability is modified in order to represent the influence of fracturing on interstitial fluid flows. The final matrix form of established field equations of the proposed model for unsaturated case has been encoded for this particular purpose, in a finite element program which had been developed for dry and saturated soils previously.
International Journal of Solids and Structures, 2010
Multiphase porous medium Thermo-hydro-mechanical behaviour Linear elastic behaviour a b s t r a c... more Multiphase porous medium Thermo-hydro-mechanical behaviour Linear elastic behaviour a b s t r a c t In this paper, the closed form two-dimensional fundamental solutions for a non-isothermal unsaturated deformable porous medium have been derived for a symmetric polar domain in both Laplace transform and time domains. The governing differential equations of the non-isothermal unsaturated soil consist of equilibrium, moisture, air and heat transfer equations including the suction effect, temperature effect and dissolved air in water. The derived fundamental solution has been verified mathematically by comparison with the previously presented corresponding fundamental solutions in three limiting cases including the steady-state thermo-hydro-mechanical, steady-state hydro-mechanical and elastostatic fundamental solutions. Also these 2D kernel functions are tested in comparison with a finite element method (FEM).
Annals of Solid and Structural Mechanics, 2010
The ''THHMD'' damage model presented in this article is dedicated to non-isothermal unsaturated p... more The ''THHMD'' damage model presented in this article is dedicated to non-isothermal unsaturated porous media. The proposed frame is based on the use of independent state variables (net stress, suction and thermal stress). Stress/strain relations are derived from a postulated expression of the free energy, accounting for the existence of residual strains. The damaged mechanical rigidities are computed by applying the Principle of Equivalent Elastic Energy for each stress state variable. The influence of damage on liquid water and vapor transfers is accounted for by introducing internal length parameters, related to specific damage-induced intrinsic conductivities. The ''THHMD'' model has been implemented in H-Stock Finite Element code. The mechanical aspects of the model have been validated by comparing the numerical results with experimental reference data. A nuclear waste repository model has been reproduced. The elastic predictions are in satisfactory agreement with the reference results. The parametric studies performed on damage parameters meet the theoretical expectations. Damage gets higher with higher damage rigidities. Water permeability grows with damage and with the internal length parameter.
Key Engineering Materials, 2008
International Journal for Numerical Methods in Biomedical Engineering, 2009
P e e r R e v i e w O n l y Modeling of settlement and induced matric suction in multiphase porou... more P e e r R e v i e w O n l y Modeling of settlement and induced matric suction in multiphase porous media under root water uptake effect by F.E.M
Soil Dynamics and Earthquake Engineering, 2009
It is well-known that the response of a site to a seismic solicitation depends on local topograph... more It is well-known that the response of a site to a seismic solicitation depends on local topographical and geotechnical characteristics. Many aspects of seismic site effect still need to be studied in more detail and they can be incorporated in the seismic norms after quantification. The ...
During tunnel excavation, stress redistribution produces plastic deformation and damage around th... more During tunnel excavation, stress redistribution produces plastic deformation and damage around the opening. Moreover the surrounding soil can be either saturated or unsaturated. Suction has a significant influence on the mechanical behaviour of geomaterials.
Wave Motion, 2007
This paper presents the numerical implementation of boundary element formulation for solving two-... more This paper presents the numerical implementation of boundary element formulation for solving two-dimensional poroelastodynamic problems in time domain. The derivation of the time-dependent integral equations is based on the Biot's theory and the reciprocal theorem. The analytical form of a 2D fundamental solution in time domain for porous media with incompressible components (solid particles and fluid) is derived and validated. After the analytical time integration of the fundamental solution kernels, a time-marching procedure is established. The comparison of different time interpolation functions shows that the mixed interpolation gives more stable response. In addition, the linear h method is used in order to improve the numerical stability of the proposed approach. Finally, two examples are presented to investigate the stability and the accuracy of this approach for wave propagation analyses.
Soil Dynamics and Earthquake Engineering, 2012
An extensive numerical analysis on the seismic site effects due to local topographical and geotec... more An extensive numerical analysis on the seismic site effects due to local topographical and geotechnical characteristics is carried out. 2D configurations under incidence of vertically propagating SV waves is modeled with the aid of HYBRID program, combining finite elements in the near field and boundary elements in the far field. The filling ratio and the impedance ratio effects on the modification of the seismic response of alluvial valleys are underlined. Parametric analysis is done on the central point of alluvial valleys where the critical point of response under existence of sediments stands. Specifying the amplification pattern under filling ratio effects, effective geometrical parameters are introduced. Subsequently, to assess the effect of the type of sediments on the seismic response, mechanical properties of materials are changed and impedance contrast coefficient is considered in combination with geometrical parameters. Finally, practical curves are presented for engineering applications.
Soil Dynamics and Earthquake Engineering, 2011
In this paper the coupled equations governing the dynamic behaviour of unsaturated soils are deri... more In this paper the coupled equations governing the dynamic behaviour of unsaturated soils are derived based on the poromechanics theory in the frame of the suction-based mathematical model presented by Gatmiri (1997) and Gatmiri et al. (1998). In this formulation, the solid skeleton displacements, water pressure and air pressure are presumed as independent variables. The Boundary Integral formulations as well as fundamental solutions for such dynamic wa u p p theory are presented in this paper for the first time. The boundary integral equations are derived via the use of weighted residuals method in a way that permits an easy discretization and implementation in a Boundary Element code. Also, the associated two dimensional (2D) fundamental solutions for such deformable porous medium with linear elastic behavior are derived in Laplace transform domain using the method of Hörmander. Finally, some numerical results are presented to show the accuracy of the proposed solutions. The derived results are verified analytically by comparison with the previously introduced corresponding fundamental solutions in elastodynamic limiting case.
Soil Dynamics and Earthquake Engineering, 2007
Results of an extensive numerical study on the 2D scattering of seismic waves by local topography... more Results of an extensive numerical study on the 2D scattering of seismic waves by local topography are presented. The investigation has been conducted using the direct boundary element method. Several types of topography (slopes, canyons and ridges) are considered. The influences of some key parameters, such as exciting frequency and geometry of the irregular feature, on surface ground motion are
Soil Dynamics and Earthquake Engineering, 2008
This paper deals with the evaluation of seismic site effects due to the local topographical and g... more This paper deals with the evaluation of seismic site effects due to the local topographical and geotechnical characteristics. The amplification of surface motions is calculated by a numerical method combining finite elements in the near field and boundary elements in the far field (FEM/BEM). The numerical technique is improved by time truncation. In the first part of this article, the accuracy and the relevance of this optimized method are presented. Moreover, parametric studies are done on slopes, ridges and canyons to characterize topographical site effects. The second part deals with sedimentary valleys. The complexity of the combination of geometrical and sedimentary effects is underlined. Extensive parametrical studies are done to discriminate the topographical and geotechnical effects on seismic ground movement amplifications in two-dimensional irregular configurations. Characteristic coefficients are defined to predict the amplifications of horizontal displacements. The accuracy of this quantitative evaluation technique is tested and discussed. r
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Papers by Behrouz Gatmiri