Abstract
To research the dynamic response characteristics of cylindrical coal-rock samples under impact loads, the impact of rigid bars on cylindrical coal-rock samples is simulated under different speed conditions, based on LS-DYNA software, and the dynamic distribution characteristics of the stress, strain, and energy of cylindrical coal-rock samples are analyzed. The results demonstrated the following: (1) the cylindrical coal-rock sample failed at the center first, and the damage developed downward along the axial direction. (2) The critical effective stress and strain have an exponential function relationship with the velocity, and the critical time has a linear relationship with the velocity. (3) The energy change law of the cylindrical coal-rock sample is consistent with the destruction morphology. (4) The axial stress peaks in the severe damage part have a linear relationship with the speed, the axial stress attenuates rapidly after passing the stress yield point, and the axial strain does not increase continuously. (5) The peaks stress and strain on the central axis and the radial line obey the power function distribution, the axial stress produces tensile stress in the axial propagation direction, and the axial stress and strain peaks at the same position are larger than those of the radial stress and strain peaks. This research provides a reference for studying coal and rock dynamic disasters.
Highlights
In the part where the cylindrical coal-rock sample is severely damaged by impact loading, the axial stress attenuates rapidly after passing the stress yield point, and the axial strain does not continuously increase, which is different from the constant increase in the strain under static loading
E distribution of the axial stress peak, radial stress peak, axial strain peak, and radial strain peak at fourteen element points on the central axis of the cylindrical coal-rock sample are shown in Figures 14 and 15, respectively. e axial stress peak, radial stress peak, axial strain peak, and radial strain peak distribution of the central axis are in accordance with the Farazdagiharris-type power function, and the correlation coefficient square (R2) is greater than 0.98. e axial stress peak at the same position is greater than the radial stress peak, and the axial strain peak is greater than the radial strain peak
The effective stress of the cylindrical coal-rock sample moves from the edge of the contact surface to the center and reaches the maximum stress at this location. en, the coal-rock samples break at the center, and the damage develops downward along the axial direction
Summary
Received 17 August 2020; Revised 1 December 2020; Accepted 4 December 2020; Published 16 December 2020. Li et al [28] demonstrated the strain, stress, displacement, vibration velocity, and energy distribution in all directions of cylindrical coal-rock samples in high-order P-waves It can be seen from the above literature that SHPB experimental research has difficulty monitoring the dynamic change process of various parameters at the internal points of the sample. Research on the damage mechanism of coal-rock samples under dynamic loading has mostly focused on the overall shape after failure and the overall stress, strain, energy dissipation, and compressive strength during the failure process. E cylindrical coal-rock sample impact experiment based on the HJC model was simulated by LS-DYNA software, and the failure characteristics and internal dynamic response characteristics of the cylindrical coal-rock samples during the failure process were analyzed. Note. ρ0, fc∗, G, N, K1, K2, and K3, D1 and D2, Pc,σmax, Smax, A, B, C, uc, T, and Pmin are defined as the density, quasi-static uniaxial compressive strength of coal, shear modulus, pressure hardening exponent, constants used for the material with no voids, damage constants, pressure, failure principal stress, normalized maximum strength, normalized cohesive strength, normalized pressure hardening coefficient, strain rate coefficient, volumetric strain, tensile strength, and minimum failure pressure, respectively
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