Study On The Formation Mechanism Of Rock Explosion Crater Under Combined Static And Dynamic Loading

Deep rock engineering,such as deep mining,deep tunneling and deep water conservancy and hydropower projects,continue to increase.Both from the perspective of engineering safety and from the perspective of economic benefit,the cracking behavior of rock must be understood during the process of deep rock engineering construction.At present,the study of deep rock fracture is mostly based on pure static or pure dynamics.Little attention is paid to the rock behavior under combined initial static stresses and dynamic loads such as external impact loading or blast loading.Therefore,this paper focuses on the main line of the formation of rock explosion crater under static stress status.The cracking behavior of sandstone subjected to the impact loading of Hopkinson bar under static stress and the blasting fragmentation of cement mortar under static stress were studied by experimental studies and numerical simulation.The purpose of this study is to explore the phenomena and laws of rock under static status during the dynamic cracking process,and to reveal the failure mechanism of rock under combined static and dynamic loading.The study includes:(1)Dynamic fracture tests of sandstone blocks under combined action of uniaxial static stresses and dynamic stresses were carried out.The initiation,propagation and coalescence of the surface cracks were observed by an ultra-high-speed camera.The effects of static stress and dynamic stress on the crack propagation behavior and the size of rock failure zone were studied respectively.(2)The equal biaxial static stress and impact load were applied to the sandstone blocks by the experimental system.The propagation of surface crack was observed by the ultra-high-speed camera,and the dynamic fracture behavior of specimens under equal biaxial static stress was analyzed.The variation of the geometric size of the sandstone block failure zone with the static stress and the dynamic stress was studied.(3)The impact cracking behavior of sandstone under static stress was simulated by the software LS-DYNA.The numerical model consistent with the experiment was established.The implicit-explicit calculation method was used to simulate the impact cracking behavior of sandstone specimens under various static stresses.The results of numerical simulation and experiments were compared to verify the effectiveness of the numerical method,and the initiation and propagation of cracks internal the rock mass were analyzed.(4)Spherical explosion model experiments under various static compressive stresses were carried out.The cement mortar material was used to prepare experimental model to simulate the rock block,and the explosives were mixed by RDX and potassium picrate in a mixture ratio of 1:1.The variations of the explosion crater shape and volume,as well as the crack distribution of the blasting crater,were investigated under different static stress states,stress levels and material strength.(5)The numerical simulation of cement mortar specimens blasting was carried out by the software LS-DYNA.By comparing the numerical results with experimental results,the practicability and effectiveness of the numerical simulation method were verified.The damage evolvement process internal cement mortar specimen was analyzed,and the formation mechanism of blasting crater under static stress was revealed.