深部大理岩真三轴力学特性离散元和有限差分耦合分析OA北大核心CSTPCD

To study the dynamic mechanical properties of deep marble,the micro parameters of deep marble were calibrated based on the coupling method of discrete element (particle flow code,PFC) and finite difference (fast Lagrangian analysis of continua,FLAC). Then,the dynamic stress equilibrium condition and uniformity assumption in the simulated three-dimensional split Hopkinson pressure bar (SHPB) test are numerically validated. Finally,an in-depth analysis is conducted on the stress-strain response,fracture characteristics,and energy evolution mechanism of marble under true triaxial stress environment. It is found that the numerical results of the true triaxial SHPB test based on the PFC-FLAC coupling theory satisfy the assumption of stress uniformity,and the simulated stress-strain curves are highly consistent with the measured ones. Peak stress and peak strain decrease with the increase of pre-pressure in the impact direction (axial pressure hereafter). At the same axial pressure,the peak stress gradually drops down with the increase of incident stress;when the incident stress is fixed,the axial pressure weakens the peak stress of the sample,while the lateral pressure perpendicular to the impact direction increases the compressive strength. During the loading process,the outbreak period of acoustic emission events generally occurs in the post-peak stage,and during this stage,a relatively obvious macroscopic fracture zone is formed within the sample. Under a true triaxial dynamic compression,the samples are mainly characterized by tensile cracks,accounting for over 80％ of the total number of cracks. The sample undergoes energy changes from loading to failure. At the peak stress point,the strain energy storage reaches its limit,which is then transformed into an energy form dominated by dissipated energy and supplemented by particle kinetic energy. The relevant conclusions have important guiding significance for the study of the dynamic characteristics of deep marble and the long-term stability evaluation of deep rock engineering.