A Study On Numerical Simulation Of Geomaterials Strain Localization

Strain localization is a well known phenomenon, generally associated with plastic deformation and rupture in solids, especially in geomaterials. In laboratory tests, the macro shear bands can be seen clearly during the collapse of the specimens. The slide damage of enbankment and foundation, the fold and fault of mountain movement, etc, can be considered as the formation of local shear bands. In past, many numerical simulation methods on geomaterials strain localization are used. Every method has its characters. In this paper, numerical simulation of geomaterials strain localization and its influencing factors are studied systematically. According to the contents mentioned above, the main works and results are as follows:First, the domestic and oversea research state on strain localization is looked back in physical experiments, theory analysis and numerical simulations. In numerical simulation of strain localization, the simulation methods can not follow the step of the computing need of discontinuous deformation. In order to simulate the strain localization, the computing techniques and constitutive equations must be improved. It causes the difficulty and inconvenience in numerical simulation of strain localization. In this paper, the software of FLAC is used to carry out the numerical simulation of strain localization using general constitutive equations.Second, during numerical simulation of geomaterials strain localization, the modify Cam-Clay model and strain-softening Mohr-Coulomb model are used. The modify Cam-Clay model is a elasto-plastic model, it can reflect the deformation character of normal consolidation and low overconsilidation clay. Strain-softening Mohr-Coulomb model is a particular form of the Mohr-Coulomb model in which some or all of the zone yielding parameters, cohesion, friction, dilation and tensile strength can be modefied after the onset of plasticity. The characters of geomaterials strain localization can be reflected using two models and the formation of shear bands can be simulated.Third, the software of FLAC^3D is good at simulation of large deformation, but it has shortage in other aspects. The preprocessor and postprocessor of FLAC^3D are not very powerful. In this paper, some models are modeled and meshed by ANSYS+CivilFEM. Based on the little interface program designed by author, Tecplot is used to carry out postprocess to generate the contours figure of shear bands.Fourth, the shear bands of clay are simulated under plane strain condition and the influencing factors such as consolidation state, end restriction, element grids, load pattern, inner and outer flaw, model thickness are analyzed. The inclination angle of shear band is analysed theoretically using classical Mohr-Coulomb and Roscoe methods and compared to the simulated inclination angle of shear bands. The simulated inclination angle is in acord with the result of Mohr-Coulomnb method.Fifth, the shear bands of rock specimens are simulated under plane strain condition, uniaxial compression condition and conventional triaxial compression condition. The influencing factors to shear bands such as element grids, loading strain rate, end restrain, ratio of height to width, confinement pressure and contact stiffness are studied. The results are satisfying and some are accord with the test and simulation results of predecessor.In all, the software of FLAC can simulate the strain localization using general constitutive equations. Through the systemic research to the influencing factors, the strain localization are understood deeply and it is useful to study the geomaterials strain localization and its engineering application.