Numerical simulation of interaction between ore-rock granular and surrounding rock in goaf of caving method

The caving mining method draws ore under the overburden,leaving the collapsed surrounding rock mass in the upper goaf,thus supporting the hanging and footwall surrounding rock.Under the conditions of different ore body shapes,rock mass strengths,and flow states of ore and rock masses,the supporting effect of the ore-rock granular is different,which leads to the difference between the damage scope of the caving goaf and the ground pressure appearance of the underground stope.The stress concentration areas and hanging wall collapse areas will pose significant risks to the subsequent mining.In view of this,based on the assumption of microcrack damage at the crack tip,the discrete element numerical simulation method is adopted to compare and analyze the interaction between the ore body and surrounding rock and the failure mode of surrounding rock in the process of ore drawing under the conditions of different surrounding rock strength,different mined-out area dip angle and whether backfill or not.The results show that the stress distribution in vertical or steeply inclined goafs is relatively uniform,while there is a stress-relaxed area at the top of the hanging wall and a stress concentration zone at the bottom of the hanging wall in the inclined goaf;for the surrounding rock with high strength,the stress distribution is relatively uniform,while the hanging wall surrounding rock will be damaged earlier when the surrounding rock strength is low,thus releasing strain energy and not easy to produce stress concentration areas.For the surrounding rock with low strength,the waste rock can be backfilled in time to reduce the deformation of surrounding rock,delay the stress concentration trend at the bottom of hanging wall surrounding rock,and delay the failure time.The research conclusion has important reference significance for controlling the ground pressure of stopes using caving mining method.