Hans Muhlhaus

The University of Queensland, Australia, School of Earth Sciences, Emeritus

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2004-Present Director, ESSCC, School of Earth Sciences, The University of Queensland2002-Present: Professor, ESSCC, The University of Queensland1993-2009: Chief Research Scientist (M), CSIRO, Exploration and Mining (part time 2002-2009)1991-1993: Senior Principal Research Scientist, CSIRO, Geomechanics 1988-1991: Principal Research Scientist, CSIRO, Geomechanics Academic qualifications: 1987: Dr. Ing. Habil. (Habilitation in Geomechanics), Karlrsruhe University 1980: Dr. Ing. (cum laude) Civil Engineering, Karlsruhe University1974: Dipl. Ing. Civil Engineering, Karlsruhe University

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Nicolas Coltice

École Normale Supérieure

Hemin Koyi

Uppsala University

Paul E. Olsen

Columbia University

Gabriel Gutierrez-Alonso

University of Salamanca

Tomoaki Morishita

Kanazawa University

Krishnakanta Kshetrimayum

Assam University

Beata Gruszka

Adam Mickiewicz University in Poznań

Stephen W Merkel

Vrije Universiteit Amsterdam

Rushikesh Golekar

University of Mumbai

Nikolaus Egel

Universität Münster

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Papers by Hans Muhlhaus

A Model for Trap Door Flow from a Deep Container

Springer series in geomechanics and geoengineering, 2019

Computational simulations of trap door flow in cohesive frictional, materials are presented. We f... more Computational simulations of trap door flow in cohesive frictional, materials are presented. We focus on flows where the extraction volume is generated by dilatancy. The dilatancy is caused by micro-cracking associated with the loss of cohesion at the onset of flow and/or the transition of the granulate into a more mobile, more loose packing order. The material behavior is modelled as a non-Newtonian fluid including rigid plastic behavior as a limit case. A rate dependent cohesion term considers the fluid like behavior if collisions dominate the intergranular momentum transfer. The simulations are based on an implicit particle-in-cell finite element code [1] developed by the second author. The implementation of the model equations is benchmarked against an analytical solution for gravity driven flow in an infinite chute.

Generalised homogenisation procedures for granular materials

Journal of Engineering Mathematics, Jul 1, 2005

Engineering materials are generally non-homogeneous, yet standard continuum descriptions of such ... more Engineering materials are generally non-homogeneous, yet standard continuum descriptions of such materials are admissible, provided that the size of the non-homogeneities is much smaller than the characteristic length of the deformation pattern. If this is not the case, either the individual non-homogeneities have to be described explicitly or the range of applicability of the continuum concept is extended by including additional variables or degrees of freedom. In the paper we model the discrete nature of granular materials in the simplest possible way by means of finite-difference equations. The difference equations may be homogenised in two ways: the simplest approach is to replace the finite differences by the corresponding Taylor expansions. This leads to a Cosserat continuum theory. A more sophisticated strategy is to homogenise the equations by means of a discrete Fourier transformation. The result is a Kunin-type non-local theory. In the following we analyse these theories by considering a model consisting of independent periodic 1D chains of solid spheres connected by shear translational and rotational springs. It is found that the Cosserat theory offers a healthy balance between accuracy and simplicity. Kunin's integral homogenisation theory leads to a non-local Cosserat continuum description that yields an exact solution, but does not offer any real simplification in the solution of the model equations as compared to the original discrete system. The rotational degree of freedom affects the phenomenology of wave propagation considerably. When the rotation is suppressed, only one type of wave, viz. a shear wave, exists. When the restriction on particle rotation is relaxed, the velocity of this wave decreases and another, high velocity wave arises.

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Emergent Anisotropy and Flow Alignment in Viscous Rock

by Louis Moresi and Hans Muhlhaus

Pure and Applied Geophysics, 2004

A novel class of nonlinear, visco-elastic rheologies has recently been developed by Mühlhaus et a... more A novel class of nonlinear, visco-elastic rheologies has recently been developed by Mühlhaus et al ([1,2]; see 1 for preprints). The theory has originally been developed for the simulation of large deformation processes including folding and kinking in multi-layered visco-elastic rock. The orientation of the layer surfaces or slip planes in the context of crystallographic slip is determined by the normal vector-the so-called director-of these surfaces. Here the model [1,2] is generalized to include thermal effects; it is shown that in 2D steady states the director is given by the gradient of the flow potential. The model is applied to anisotropic simple shear where the directors are initially parallel to the shear direction. The relative effects of textural hardening and thermal softening are demonstrated. Turning to natural convection we compare the time evolution and approximately steady states of isotropic and anisotropic convection for a Rayleigh number Ra =5.64Xb10 5 . The isotropic case has a simple steady state solution, whereas the orthotropic convection model produces a continuously evolving patterning in the core of the convection cell, which makes only a near-steady condition possible. 1) http://www.ned.dem.csiro.au/research/solidmech/Publications/.

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Spatial coupling and propagative plastic instabilities

Finite element modelling of 3-D convection problems in fluid-saturated porous media heated from below

Communications in Numerical Methods in Engineering

ABSTRACT

Computational plasticity

Shear bands in a rigid plastic material in a simple shear test

A Breakage Diffusion Model for Strength Softening Rock

A generalised version of the gradient plasticity model by Muhlhaus and Aifantis [4] is proposed. ... more A generalised version of the gradient plasticity model by Muhlhaus and Aifantis [4] is proposed. As an example, simple shear with a weak zone of reduced cohesive strength around the center of the shear layer is considered. Details of the formulation, implementation and numerical and analytic results are presented. The results include unexpected elements, which are interpreted in terms of a partial (analytic) solution of the governing equations.

Particle in cell and discrete element models for granular materials

Texture alignement in simple shear

We illustrate the flow behaviour of fluids with isotropic and anisotropic microstructure (interna... more We illustrate the flow behaviour of fluids with isotropic and anisotropic microstructure (internal length, layering with bending stiffness) by means of numerical simulations of silo discharge and flow alignment in simple shear. The Cosserat theory is used to provide an internal length in the constitutive model through bending stiffness to describe isotropic microstructure and this theory is coupled to a director theory to add specific orientation of grains to describe anisotropic microstructure. The numerical solution is based on an implicit form of the Material Point Method developed by Moresi et al. [[1]].

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