A Numerical Study on the Dynamic Brazilian disc test using a Statistical Bonded Discrete Element Method

  • Wessling, Albin (Luleå University of Technology)
  • Larsson, Simon (Luleå University of Technology)
  • Kajberg, Jörgen (Luleå University of Technology)

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Numerical modelling and simulation of dynamic rock fracture can give insight about several industrial excavation processes, such as drilling in the mining industry. A characteristic of the mechanical behaviour of rock materials is the unpredictability of measurements, e.g., with regards to measured strength and fracture pattern, and a numerical model should be able to capture this. An example of such a numerical method is the heterogeneous Bonded Discrete Element Method (BDEM) [1,2]. In this model, the heterogeneous rock grain structure is represented through spherical discrete elements bonded together to form subsets of irregular shapes and sizes with mechanical properties given from the Weibull distribution, see Figure 1. Compared to previous work with this model, where quasi-static mechanical behaviour of rock has been studied, this work extends the model to include the dynamic mechanical behaviour. Model parameter calibration is performed by simulating the Brazilian disc test at elevated strain rates in a split-Hopkinson pressure bar system [3]. Further, a parametric study is conducted on the heterogeneity index and grain cement strength. By comparing the simulation to experimental results, it is shown that this modelling approach can capture key features of the dynamic Brazilian disc test, such as the indirect tensile strain, the overloading effect and final crack surfaces. It is shown that the overlading effect can be estimated from the indirect tensile strain measurement, making it possible to obtain a more appropriate measurement of tensile strength.