Numerical modelling of dynamic spalling test on rock with an emphasis on the influence of pre-existing cracks

Abstract

Summary. This article deals with numerical modeling of rock fracture under dynamic tensile loading and the related prediction of dynamic tensile strength. A special emphasis is laid on the influence of pre-existing natural microcrack populations as well as structural (artificial) cracks. For this end, a previously developed 3D continuum viscodamage-embedded discontinuity model is employed in the explicit dynamic finite element simulations of the spalling test. This model is capable of modelling the effect of natural microcracks populations always present in rocks as well as to capture the strain rate hardening effect of quasi-brittle materials. In the numerical simulations of spalling test on Bohus granite, it is shown that the model can predict the pullpack velocity of the free end of the intact rock sample and the effect of structural cracks with a good accuracy. According to the simulations, the effect of microcrack populations, modeled here as pre-embedded discontinuity populations, is weaker than the corresponding effect under quasi-static loading.

Numerical Modeling of Concrete Spallation at Medium Strain-rate

“…As regards stability and fracture research, one of the main material properties of quasi-brittle materials, such as rock and concrete, is the dynamic tensile strength. There are several theoretical approaches to, directly and indirectly, calculate the rock's dynamic tensile strength, see [2] for more details. Spalling test using the Modified Split Hopkinson Bar (MSHB) is one of the direct tests to measure the dynamic tensile strength of brittle materials such as concrete, mortar, and rock at medium strain rate [3].…”