Dynamic Response Simulation Of Induced Caving Roof With Continuous Mining Under Mining Unloading

The excavation of the underground rock mass is a typical unloading mechanical process that brings redistribution of initial rock stress field. For this kind of problem, the traditional method of load analysis ignored the influence of unloading, which leads to the inconsistency between theoretical analysis and engineering practice. The technology of blast-induced caving roof which based on continuous mining is an innovative and efficient method. But the inducted rock mass, as engineering object which shows typical unloading features. Therefore, to better assure safety in practice of this technology, unloading analysis should be taken in the inducted rock mass, and the stability of the rock mass system, the deterioration laws of rock mass quality and disturbance mechanics effect of rock mass should be clearer understood. Took the No.92 ore body which adopted the blast-induced caving roof technology based on continuous mining in Tongkeng Mine as the experimental subject, by using the guidance of unloading rock mechanics theory, discussed the question of e induction effect of the rock mass engineering of underground mine. The main research contents as follows:The mechanics parameters deterioration laws of rock mass were studied, the unloading region of inducted rock mass was divided by the affect region theory, the method and flow of unloading mechanical analysis was analyzed.The continuous mining FE model of No.92 ore-body in Tongkeng mine was established, unloading effect was simulated using dynamic mechanical parameters. The result shows:the maximum tensile stress, subsidence displacement and equivalent plastic strain of roof rock mass were 1.5Mpa,20cm and 1.5el0-2 in the unloading analysis, and 1.OMpa, 13cm and 0.9e10-2 in conventional analysis; The values of unloading analysis are greater than conventional analysis, but closer to the actual situation; the maximum step in continuous mining is 48m which shows the roof should be inducted after 2 mining steps.Based on the continuous mining-induced caving roof option of the No.92 ore body in Tongkeng mine, by using Implicit-Explicit sequence calculation of ANSYS/LS-DYNA software, the mechanics responding law of inducted rock mass and its stress field was studied under the blasting loading on the condition of coupling effect by perturbation stress field and initial earth stress field.On the basis study of rock dynamic strength and failure criterion, the material constitutive model based on H-J-C damage model and dynamic damage of rock mass were established; The calculation model of single-hole was established, and blasting damage and fracture development of inducted rock mass was studied. The calculation model of pre-splitting crack was established, too. The forming process of pre-splitting crack and mechanic effect were analyzed, and the numerical result is verified by the experiment result of the borehole camera system.