Calibrating the Strength Ratio and the Failure Envelope for DEM Modeling of Quasi-Brittle Materials
Haiying Huang
Civil and Environmental Engineering, Georgia Institute of Technology
CSE Distinguished Scientists and Engineers from Underrepresented Groups Speakers Program, 2018-19
ABSTRACT: A common issue in numerical modeling with the distinct element method (DEM) based on spherical particles is that the largest compressive-tensile strength ratio (UCS/UTS) is only about 3-5, if the interactions between the particles are limited to short-range, elasto-perfectly brittle and frictional. The associated failure envelope generally fails to capture the high nonlinearity in the low confining stress range, typical for quasi-brittle materials such as rocks and concretes. This deficiency may not be an issue for a DEM simulation if the macro-scale failure involved in the problem of interest is in a single mode, namely, either solely shear failure governed plastic flow or tensile fracturing. However, rock failure in general could involve both plastic flow and tensile fracturing. The strength ratio, which can be viewed as a measure of material brittleness, then affects the transition from one mode of failure to the other. Huang shows that a realistic strength ratio and the associated nonlinear failure envelope at low confinement can, in fact, be achieved by implementing a displacement-softening contact law within the conventional framework of soft particle DEM.
