A coarse-grained bonded particle model for large-scale rock simulation

For solving the computationally intensive problem encountered by the discrete element method(DEM)in simulating large-scale engineering problems,it is essential to establish a numerical model that can effectively simulate large-scale rocks.In this study,the coarse-graining effect of a linear-Mindlin with bonding model was studied in the unconfined compression strength(UCS)and Brazilian tensile strength(BTS)tests.We found that the main reason for the coarse-graining effect of the BTS tests is that the type I fracture toughness is positively correlated with the size of the particles.Based on the results analysis and fracture mechanics,the coarse-grained(CG)modeling theory was combined with a bonded particle model(BPM)for the first time and a coarse-grained bonded particle model(CG-BPM)was developed,which can be effectively used to model the tensile strength of large-scale rocks with different particle sizes.The excavation damage zone(EDZ)in an underground research laboratory(URL)was selected as an application case,which shows that the coarse-grained bonding model presented in this paper is more accurate and reliable than the traditional one in large-scale rock simulation,at least in the scenario where tensile failure is dominant.

Advanced stability analysis method for the tunnel face in jointed rock mass based on DFN-DEM

An advanced stability analysis of surrounding rock can assure safe construction in tunnels.However,in traditional analysis methods,geometric information on the rock mass discontinuities is obtained by a geological compass and treated as an infinitely expanded plane in a numerical simulation,which is inaccurate in both geometric and numerical models.To solve this problem,this paper studied a control network and an image stitch method to assess the accuracy of a geometric model and proposed a more accurate method to obtain the geometric information of rock mass discontinuities based on digital photogrammetry.Based on discrete fracture network and discrete element method(DFN-DEM),this paper treated the rock mass discontinuities obtained by digital photogrammetry as finite disk planes and simulated the excavation process of the Qianyu tunnel.According to the simulation results,this paper determined the specific location of the collapse disaster on the tunnel face,which is of great significance to tunnel support design.Comparing the deformation of the surrounding rock mass on the tunnel face in the simulation results with the actual situation,this paper verified the feasible accuracy of this method in analysing the stability of the surrounding rock mass on a tunnel face in advance.