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• A new hysteretic damping model is proposed. • The critical hysteretic damping coefficient acquisition method is proposed. • The effects of different hysteretic damping ratios on the simulation results of quasi-static tunnel excavation and quasi-dynamic rock slope slip are investigated. In the field of mechanical numerical simulation, damping is always a vital parameter. However, in the combined finite-discrete element method (FDEM), the current application of damping is insufficient. Therefore, in this paper, a new hysteretic damping model and its corresponding critical damping coefficient acquisition method are proposed. Furthermore, simulations of quasi-static tunnel excavation and quasi-dynamic rock slope slip are employed to investigate the influence of different hysteretic damping ratios on the numerical results. The study results show that the new hysteretic damping model, which is independent on the calculation time step, considers the effects of the element size, Young's modulus and material density and can obtain the critical damping coefficient by comprehensively using cantilever beam vibration numerical modelling and theoretical equations. In addition, the sensitivity of quasi-static tunnel excavation to the hysteretic damping ratio is very weak; however, for quasi-dynamic rock slope slip simulation, the damping ratio η has a substantial influence on the simulation results. The new hysteretic damping model proposed in this paper is important for improving the accuracy of FDEM numerical simulation results, especially for quasi-dynamics simulation. [ABSTRACT FROM AUTHOR]

Grouting is widely used to reduce hydraulic conductivity and enhance the strength of rock masses in geotechnical engineering. With the depletion of shallow resources and expansion of human activities, more underground projects are operated in deeper underground under high in-situ stress conditions. Understanding and controlling the grout penetration process under high in-situ stress conditions are critical to optimizing the grouting process in deep underground projects. In this work, we develop a FDEM-grouting model to study the effect of in-situ stress conditions on the grout penetration process by combining the combined finite-discrete element method (FDEM) with a grout simulator. The ability of FDEM-grouting to model grout penetration in fracture networks is confirmed by numerical tests compared with analytical solutions. The necessity of considering the effects of the fracture roughness, in-situ stress and HM coupling on the grout penetration process are discussed. A persistent fracture network is designed to investigate the grout penetration process under various in-situ stress conditions. The results show that the in-situ stress conditions can greatly affect the grout penetration in fracture networks. The anisotropic grout penetration under in-situ stress conditions is potentially useful for improving the grouting design. [ABSTRACT FROM AUTHOR]