Study On Nonlinear Deformation And Damage Of Rock Under Impulse Loading

In modern geotechnical engineering, mine blasting, impact causes the rock to break, military engineering protection, and natural disasters such as earthquake, rock burst, the essence of these problems lies in the propagation of stress pulse in the rock, witch lead to rock nonlinear deformation damage and destruction, and in engineering practice it has been subjected to repeated shocks before the destruction of the rock.So the study of the rock under impact loading and cyclic impact load of nonlinear deformation damage has a contribute to the design of impact breaking rock machine, the selection of process parameters in the process of construction, anti breaking project safety design, and also provide reference data and theoretical basis for other rocks related to the subject of the research.In this paper,firstly, in order to acquire a numerical test model of rock SHPB test firstly, by using the LS-DYNA nonlinear dynamic analysis software to optimize the experimental device, and the selection of the parameters of the constitutive model is discussed. Then the dynamic failure process of rock and the failure modes of rock under different strain rates are analyzed, also the energy dependence analysis is carried out. Finally, the numerical model of rock under cyclic impact loading is discussed, including the advantages and disadvantages of the two models, the influence of rock damage on the stress wave propagation and the characteristics of rock failure.The study shows that in the numerical simulation of dynamic failure of rock, the selection of HJC model parameters of rock material is suitable for the SHPB experimental system. The half sine wave can be used to solve the problem of the dispersion effect of stress wave propagation in the pressure bar, and when half sine wave is used, the time of the specimen to reach the stress uniformity is shorter; Rock failure process and failure mode has been different at different strain rates, embodied in the formulation of the crack position, the development direction of fracture, crack at different positions in the development speed and the termination of the fragment shape, quantity, size, etc. aspects after the destruction of termination; The absorption energy of rock can be correlated with the peak value of incident stress and the duration time. If the incident energy is enough to destroy the rock, the energy efficiency of rock failure is higher when the stress wave loading with high amplitude and low duration.Rock after subjected to shock loading causes rock damage, meso crack appears to nucleate and crack and the deterioration of material properties leads to the peak value of stress wave. When the rock is destroyed under the cyclic impact load, the crack is generated from the axis position, which is different from the failure mode under single impact.