Calibration Of Constitutive Parameters Of Granite JH-2 And Numerical Simulation Of Damage Characteristics Under Repeated Loads

Under the action of explosion and penetration,rock often appears cracking,breaking and failure.This kind of problem is very complicated.Study the process of dynamic response of rocks under cyclic loading?such as repeated penetration and cyclic blasting?is of great significance to the construction of various protective engineering and civil engineering.This paper adopts the method of combining rock dynamics theory and numerical simulation to carry out the above main problems,and the research work and conclusions are mainly:Firstly,elaborate Johnson-Holmquist??JH-2?materials tensile fracture model and the softening model coupling mechanism,based on the basic physical and mechanical experiment related to granite,the constitutive parameters of the theoretical calculation method and experience method,preliminary sure JH-2 and tensile fracture to soften the coupling constitutive model parameters,and by using the nonlinear dynamic analysis software AUTODYN the target plate rock penetration of different working conditions,the numerical simulation,the sensitivity analysis to research the coupling constitutive parameters.The research results show that the sensitivity degree of each parameter of JH-2 and tensional fracture softening coupling constitutive is different from the evaluation index of the calculation results.Among them the parameters that have great influence on the residual velocity and penetration depth sensitivity are?,G,HEL,K₁,A,N,B and M.Then,the finite element software AUTODYN,based on FEM-SPH coupling algorithm and granite JH-2 and tensile fracture softening coupling constitutive structure,was used to conduct numerical simulation of projectile penetrating rock target plate,so as to study and analyze the dynamic response of granite target plate under repeated penetration.The calculation results show that under the projectile velocity of 220m/s?Vs?420 m/s,the failure mode of"conical crater+tunnel"formed during the initial penetration of multiple bullets into granite target plate provides a prerequisite for subsequent repeated and stable penetration.With the increase of impact times,the absolute penetration depth gradually increases while the relative penetration depth decreases each time,and the more impact times or the higher impact velocity,the more stable the penetration process of the projectile body is.The concept of relative penetration coefficient and the theoretical formula of repeated penetration depth based on impact number and projectile velocity are of practical value.Finally,ANSYS/LS-DYNA analysis software and full restart function were used,and Holmquist-Johnson-Cook?HJC?constitutive model was adopted to conduct numerical simulation of rock cycle blasting problem,so as to explore the cumulative damage evolution mechanism and distribution rule of rock under the dynamic load of cyclic blasting.The results show that the extent of the fracture zone is larger than that of the crushing zone under the action of multiple blasting.With the increase of the number of cycles,the rock damage accumulation evolution cloud shows an uneven annular damage area in the periphery of the fracture area,and the range of total damage area obtained from the cumulative damage curve shows a sudden development after a certain number of cycles of blasting,indicating that the cumulative effect of rock damage accumulation is different in different areas under the superposition of blasting load.In the radial direction,the cumulative damage increment presents a Weibull distribution of single peak and positive deviation,and it is mainly concentrated in the middle of the total damage area.Under different blast center distances,the cumulative damage increment of rocks has a non-linear correlation with the number of cycles,and gradually becomes stable with the increase of the number of cycles.