Proceedings of the 8th World Congress on Computational Mechanics - 5th European Congress on Computational Methods in Applied Sciences and Engineering

Atti dei Congressi Mondiali ed Europeo di Meccanica Computazionale tenuti congiuntamente a Venezia dal 30 giugno al 4 luglio 2008

Thermal effects in partially saturated soils: a constitutive model

The present paper is centred on the assessment of an elastic–plastic model for partially saturated soils, earlier proposed by the authors, for its predictive capability with respect to temperature changes, on the light of available experimental results. The model is cast within a constitutive framework that uses Bishop’s stress and suction as main variables governing the volumetric response of the material. Some enhancement to the original temperature-independent formulation is proposed. In particular, functions describing the yield surface and the compressibility modulus are modified to account for the shrinking of the elastic domain and for the increase of irreversible volumetric strain with heating. Some examples illustrate the main features of the present proposal. Comparison with some experimental results is also included

State surfaces of partially saturated soils: an effective pressure approach

State surfaces may be given by interpolation of experimental data or may represent the integration of linear or nonlinear elastic constitutive equations. Anelastic behavior may also be considered if only loading is taken into account to ensure uniqueness of the surface. State surfaces are usually defined in the (p, q, s) space, where p, q, and s represent, respectively, the excess of mean stress over air pressure, the deviatoric stress, and suction. An alternative approach assumes similar constitutive equations but defined in the space (p’, q), where p’ represents the effective pressure. This latter approach is extended to the space (p’, q, s) and improved to carefully deal with the role of suction, in conjunction with the confining pressure, in controlling soil expansion (swelling)

A microscopical model for electric-mechanical contact

In this paper a model to deal with electric-mechanical contact problems in the framework of the FEM is presented. On the basis of some micro-mechanical studies, a new approach is developed to define the non-linear constitutive law that governs the normal force-displacement behaviour and the electric resistance of the contacting surfaces

Identification of a steady-state flow in porous media using artificial neural networks (Invited lecture)

For a steady state convection problem, assuming given concentration field values in a few measurement points and hydraulic head values in the same piezometers, the source of the concentration, and its intensity are deduced using Artificial Neural Networks (ANNs). ANNs are trained with data extracted from Finite Difference (FD) solution of a classical convection problem for small Peclet number. The numerical analysis is exemplified for vanishing, homogeneous and non-homogeneous field of velocity. It is shown that the diffusivity vector can also be identified. The complexity of the problem is discussed for each studied case

Elastoplastic soil constitutive laws generalized to partially saturated states

This paper deals with the plastic behaviour of partially saturated soils by modifying an existing model for fully saturated soils. The saturated soil model, formulated in the framework of generalized plasticity, considers volumetric as well as deviatoric strain hardening and takes account of the memory of past stress history and possible limit states. The generalization of the existing model to simulate the experimentally observed behaviour of partially saturated soils has been obtained by introducing Bishop's stress and suction as independent stress parameters and by modifying the hardening parameter and the yield condition to take into account the role of suction

Discrete method for soil modelling

The interaction of the cutting tools with different geological settings determines a different wear and consequently different economical costs for the excavation. We apply here a strategy for soil modelling which is based on dis- cretization of the continuum with rigid disks and suitable contact models. We concentrate at contact level the real mechanical behaviour of the soil. In order to carry out this strategy a ”micro” and a ”macro” level are established. This paper focuses on the micromechanical model