Research on damage characteristics of coal-measure limestone under axial dynamic load

Abstract

In order to reduce the influence of engineering disturbance, blasting and other activities on the stability of surrounding rock in the process of roadway support and excavation, the damage characteristics of coal measure limestone under different impact loads were studied. Hopkinson pressure bar is used to conduct impact under different impact loads. The crushing process of limestone was simulated by LS-DYNA finite element software, and the mass fraction of each particle size, stress-strain curve, peak stress-average strain rate curve and limestone crushing process were analyzed after crushing. The results show that with the increase of the impact load, the peak stress and average strain rate gradually increase, and the fracture degree of the specimen become more serious, and the peak stress and the average strain rate show an approximate linear relationship; under different impact loads, the fracture of the specimen follows the law that the edge expands to the center and develops from the internal cracks to the outside. The failure process is divided into the crack closure stage, the approximate elastic stage, the rapid development stage of the crack and the rapid unloading stage. The crushing energy dissipation is significantly affected by the strain rate.

Keywords

• hopkinson pressure bar
• ls-dyna
• limestone
• damage characteristics
• strain rate
• axial dynamic load