FURTHER DEVELOPMENT OF GDEM FOR THE MODELING OF MULTI-SCALE DYNAMIC RESPONSE OF ROCK SUBJECTED TO BLASTING AND IMPACT

The dynamical responses of rock subjected to blasting and impact have been of concern in most underground projects. Due to the size effects and strain-rate enhancement induced by inertial effects, the dynamic responses of rock and underground structures show multi-scale characteristics. Thus, in order to achieve better understanding of multi-scale dynamic responses of rocks, both computation accuracy and numerical efficiency have been taken into account. This is achieved by further development of a continuum-discontinuous element method code, called GDEM, with a new type of dynamic bounding-surface damage model being implemented, thus forming a bounding-surface dynamic plasticity damage-GDEM model (DB-GDEM). A dynamic bounding-surface damage model is adopted, with the strength surface of Holmquist-Johnson-Cook model being employed as bounding surface. The concept of critical state, strainrate hardening, and continuum damage evolution has been taken into account for both brittle and ductile responses of rock. The model performance has been demonstrated by a few numerical simulations, including the Landau blast model, explosions under various confinements, and trapezoidal impulse loading, etc. By comparing modeling results among DB-GDEM model, linear-elastic model in GDEM, and D-P model in GDEM, it is noted that the contribution of plasticity-damage can result in the decay of stress waves and deterioration of dynamic strength. Both continuous and discontinuous mechanical behaviors of rocks have been captured well by the newly developed DB-GDEM model. The main multi-scale dynamic characteristics of rock subjected to blasting and impact, including particle movement, fragmentation of rock mass, stress-wave propagation, and failure models, have been captured. The introduction of bounding-surface plasticity damage model in GDEM would reproduce a more realistic dynamic damage response of rock compared with the original GDEM model that embedded with conventional constitutive models.