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AbstractWhen the Holmquist-Johnson-Cook (HJC) constitutive model is used to simulate limestone under the impact load, problems of a compaction stage not being characterised and low dynamic peak stress prediction accuracy are observed. The numerical simulation and experimental results were inconsistent. In this study, we proposed a modified HJC constitutive model and parameter determination method. Based on the characteristics of the dynamic stress-strain curve of limestone and relationship between axial and volumetric strains, the linear elastic phase of the state equation of the original HJC constitutive model was modified, and a new state equation was proposed. The yield surface of the original HJC constitutive model was modified on the basis of the sensitivity analysis method and limit surface theory, and a method for determining the parameters of the modified HJC constitutive model of limestone was proposed. The modified model and parameter determination method were experimentally verified using the split Hopkinson pressure bar (SHPB) and a high-speed camera. The results showed that the state equation curve of limestone under the impact load was divided into compaction, linear elastic, and fully compacted stages. After the introduction of the pressure parameters M, P, and Q, the nonlinear change in the stress-strain curve during the compaction stage was highly consistent with the SHPB results. The strength parameters fc, A, B, and N exhibited the maximum impact on the dynamic strength of limestone. After the strength parameters A, B, and N were modified for the yield surface, the prediction accuracy of limestone dynamic peak stress was over 97%, the prediction error rate decreased by more than 10%, and the reliability of numerical simulation results improved. These results can provide a simple and feasible numerical simulation method for the dynamic analysis of rock materials.

AbstractTo study the influence of drilling and blasting on the deformation of the tunnel lining in a multimedium surrounding rock section, this paper constructs the deformation calculation theory of the explosion stress wave of the tunnel lining. We select single-medium surrounding rock, multimedium surrounding rock, different explosion accelerations, and different surrounding rock grades as research variables and analyse in depth the causes of the deformation response of the tunnel lining. It is found that the stress wave causes more damage to the surrounding rock closer to the explosion point, and the disturbance to the surrounding rock increases with the increase of the acceleration of the explosion stress wave. And the better the surrounding rock grade, the more obvious the creep effect formed by the explosion stress wave, and the more damaging the stress wave propagation is to the tunnel lining. After the stress wave propagation medium changes from soft to hard, the energy will produce a “nest effect” at the interface between the two media, and the energy will accumulate briefly at the interface. When a certain amount of energy has accumulated, it propagates into the hard medium in an excited state, which causes large vibration of the tunnel lining in the soft medium area. The stress wave propagation medium changes from hard to soft, and the excessive energy in the hard medium produces huge vibration only at the junction of the hard–soft media, and there is no “nest effect.”