Carlos Labra

Discrete Element Modelling of Rock Cutting

This paper presents numerical modelling of rock cutting processes. The model consists of a tool-rock system. 3D geometry is considered in the model. The rock is modelled using the discrete element method, which is suitable to study problems of multiple material fracturing like that of rock cutting. The paper presents brief overview of the theoretical formulation and calibration of the discrete element model by simulation of the unconfined compressive strength (UCS) and indirect tension (Brazilian) tests. Numerical examples illustrate the paper. Rock cutting processes typical for underground excavation using both roadheader and TBM cutting tools are simulated. Numerical results are compared with the available experimental data.

Discrete/Finite Element Modelling of Rock Cutting with a TBM Disc Cutter

This paper presents advanced computer simulation of rock cutting process typical for excavation works in civil engineering. Theoretical formulation of the hybrid discrete/finite element model has been presented. The discrete and finite element methods have been used in different subdomains of a rock sample according to expected material behaviour, the part which is fractured and damaged during cutting is discretized with the discrete elements while the other part is treated as a continuous body and it is modelled using the finite element method. In this way, an optimum model is created, enabling a proper representation of the physical phenomena during cutting and efficient numerical computation. The model has been applied to simulation of the laboratory test of rock cutting with a single TBM (tunnel boring machine) disc cutter. The micromechanical parameters have been determined using the dimensionless relationships between micro- and macroscopic parameters. A number of numerical simulations of the LCM test in the unrelieved and relieved cutting modes have been performed. Numerical results have been compared with available data from in-situ measurements in a real TBM as well as with the theoretical predictions showing quite a good agreement. The numerical model has provided a new insight into the cutting mechanism enabling us to investigate the stress and pressure distribution at the tool–rock interaction. Sensitivity analysis of rock cutting performed for different parameters including disc geometry, cutting velocity, disc penetration and spacing has shown that the presented numerical model is a suitable tool for the design and optimization of rock cutting process.