SOIL MODELING TOOLS IN THE “LOGOS” SOFTWARE PACKAGE

Abstract

he paper gives a brief overview of material models used in computational practice for predicting the behavior of geological media under conditions of high and low pressure, complex stress conditions under quasi-static and dynamicloading, including the high-speed one. The analysis of the application areas of geomaterial models implemented in the dynamic strength software module of the “Logos” software package is performed. The models are conventionally divided into two categories. A feature of the models of the first category (Grigoryan's and Zamyshlyaev –Evteev's ground environment) is the application of pressure dependence on total volumetric deformation, like the deformation theory of plasticity. The models in this category are easy to implement.
The second category of geomaterials (Geologic Cap model, CSCM concrete, FHWA and Mohr – Coulomb models) uses the separation of elastic and plastic deformations. To calculate the increments of plastic deformations, the surface of the plastic potential is used, associated or not associated (Mohr – Coulomb model) with the loading surface. It is also possible to account for plastic volume expansion (dilatation) caused by shear stress at low all-round pressure. The shape of the shear loading surface generally includes a separation surface, a fracture shear surface and/or a lid surface and aoptional dependence on the type of stress state.
The dependence of pressure on volumetric deformation in the models of geomaterials of the first group is set directly by the user, the second group is determined by the law of plastic compressibility for the volumetric component of plastic deformation. The models of the second group are complemented by mechanisms of kinematic hardening (the concept of active and reverse stress), viscoplastic behavior (the concept of trial and inviscid stresses), and damage accumulation (the concept of effective and reduced stresses).
Examples of test calculations on a single finite element in the dynamic strength software module of the “Logos” software package are given, demonstrating the operability of the algorithms for: plasticity and taking into account the type of stress state on the CSCM geomaterial model under tension, compression and shear; viscoplasticity, damage on the CSCM geomaterial model under compression; cap, kinematic hardening on the Geologic Cap geomaterial model under compression; isotropic hardening – based on the FHWA geomaterial model under compression.