TUTCRIS - Tampereen teknillinen yliopisto


Numerical modelling of dynamic Brazilian disc test on thermal shock weakened granite

Tutkimustuotos: Konferenssiesitys, posteri tai abstrakti


TilaJulkaistu - 2017
Tapahtuma42nd Israel Symposium on Computational Mechanics - ISCM42 - Israel Institute of Technology, Haifa, Israel
Kesto: 30 maaliskuuta 201730 maaliskuuta 2017


Seminar42nd Israel Symposium on Computational Mechanics - ISCM42


Traditional drilling methods of excavation and mining engineering use mechanical loading for rock breakage. However, due to the increased demands for higher efficiency with lower costs, alternative methods based on the assistance of some other physical agents are being searched in order to improve, for example, the penetration rates and tool lives in hard rock drilling. One possibility is to weaken the rock material by a thermal shock before mechanical loading. This study presents an attempt to model the effect of thermal shock on the tensile strength of Balmoral red granite under dynamic loading.

For this end, a combined continuum damage-embedded discontinuity model capable of capturing the rate-dependent failure of brittle materials under transient loading is employed. The rate-dependency is incorporated via a continuum isotropic viscodamage model while the displacement discontinuity model governs the post peak softening regime. In the embedded discontinuity model, the determination of the displacement jump is based on bi-surface plasticity. A computationally efficient scheme is achieved by solving first the global displacement field by an explicit time integrator and then performing a local (elemental) loop for displacement jumps and stresses contributing to the global internal force vector.

Two different methods to represent the weakening effect of the thermal shock is tested. In the first, the thermal shock induced damage is represented as pre-embedded discontinuities with almost random orientation and zero strength. In the second, the material data of the mesh treated with the heat shock is assumed to be deteriorated and to conform to the Weibull distribution. The seed values of the Weibull method are damaged (due to high temperature) Young’s modulus and the strength of the rock.

These two methods are compared in the simulations of the Brazilian disc test on the thermal shock treated Balmoral red granite samples. It will be shown that the weakening effect of the thermal shock on the indirect tensile strength can be captured with both of the methods. This study thereby lays the foundation for the next step of this research project, namely the numerical modelling of the thermal shock damage process itself.