Abstract
The bonded-particle model (BPM) is a very efficient numerical method in dealing with initiation and propagation of cracks in rocks and can model the fracture processes and most of macro parameters of rocks well. However, typical discrete element method (DEM) underestimates the ratio of the uniaxial compressive strength to the tensile strength (UCS/TS). In this paper, a new DEM method with a nonlinear elastic tensile model embedded in BPM is proposed, which is named as nonlinear elastic tensile bonded particle model (NET-BPM). The relationships between micro parameters in NET-BPM and macro parameters of specimens are investigated by simulating uniaxial compression tests and direct tension tests. The results show that both the shape coefficient of the nonlinear elastic model and the bond width coefficient are important in predicting the value of UCS/TS, whose value ranging from 5 to 45 was obtained in our simulations. It is shown that the NET-BPM model is able to reproduce the nonlinear behavior of hard rocks such as Lac du Bonnet (LDB) granite and the quartzite under tension and the ratio of compressive Young’s modulus to tensile Young’s modulus higher than 1.0. Furthermore, the stress-strain curves in the simulations of LDB granite and the quartzite with NET-BPM model are in good agreement with the experimental results. NET-BPM is proved to be a very suitable method for modelling the deformation and fracture of rock-like materials.
Highlights
A clumped particle model was proposed in [2] based on the bonded-particle model (BPM), which improves the predictive capability of the Discrete element method (DEM) by successfully predicting the whole failure envelope and increasing the ratio of uniaxial compressive strength to tensile strength (UCS/TS) making it closer to that of rocks
The Lac du Bonnet (LDB) granite which are widely used for model calibration a quartzite studied in [39] under uniaxial compression and direct tension are modelled with the and a quartzite studied in [39] under uniaxial compression and direct tension are modelled with the nonlinear elastic tensile bonded particle model (NET-BPM)
(1) It is very difficult to gain a large ratio of UCS/TS more than 20 in conventional BPM model [1,2,20]
Summary
Discrete element method (DEM) is proved to be a very effective method in modelling rock-like materials [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20]. A clumped particle model was proposed in [2] based on the BPM, which improves the predictive capability of the DEM by successfully predicting the whole failure envelope and increasing the ratio of uniaxial compressive strength to tensile strength (UCS/TS) making it closer to that of rocks. Further research is required to obtain suitable UCS/TS and to capture the correct relationships between Young’s modulus and Poisson’s ratios in tension and compression for rock by DEM. A new numerical method for rock materials based on BPM is proposed which is characterized by using a nonlinear elastic model to describe the relationship between normal force and normal strain undergoing tension. Some conclusions are made in the last part of this paper regarding the performance of the NET-BPM model
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