| Overburden was dispersions bedding consist of rock and ore between roof rock and ore layer,which is one of the effective methods to control ground pressure and guarantee stope safety.Jinshandian iron mine didn't form corresponding overburden thickness before stope for surface structure and unreasonable roof caving project which result in the mining project couldn't be done smoothly,therefor,this paper use theoretical calculations and numerical simulation to research the reasonable overburden thickness based on Jinshandian iron mine east area mining technology.First of all,overburden thickness of sublevel caving without sill pillar should meet the forming of drawing ellipsoid and loosing ellipsoid,from the aspect of the ore drawing technology,overburden should satisfy the request of extrusion blasting and side ore drawing to keep the interface integrity of rock and ore and make ore surrounded by rock,from the aspect of safety,certain overburden thickness layer serves as buffer layer could filter shock wave of roof collapse,the reasonable overburden thickness in Jinshandian iron mine was 20 meters based on the theoretical calculations above.Secondly,build numerical simulation ore drawing model on condition of several different overburden thickness in PFC3 D software,in order to confirm the accuracy of numerical simulation ore drawing,an triaxial compression experiment was done in PFC3 D to obtain relevant micro parameters of ore drawing model,use fish function in PFC3 D to record ore recovery rate and depletion rate on condition of different overburden thickness,analyze the result found that the ore recovery rate and depletion indicators were optimal when the overburden thickness was 20 meters,so it's verified again that the reasonable overburden thickness in Jinshandian iron mine east area was 20 meters from the aspect of numerical simulation.Finally,based on the research results above,analyzing the rock mass cavability of upper plate surrounding rock in Jinshandian iron mine east area know that forced roof caving was needed to cave roof rock,combined with the mined-out area before-340 meter stage and surface structure in east area,a roof caving project was put forward:-270 meter sublevel was the main roof caving layer,with the mining level decline,-284 meter and-298 meter sublevel were the supplementary roof caving layer,this could confirm the overburden thickness of roof caving project reach to 20 meters.This paper combined theoretical analyze and numerical simulation to obtain reasonable overburden thickness in Jinshandian iron mining east,confirmed related roof caving project based on the overburden thickness,it provided theoretical basis of safety mining for Jinshandian iron mining,it had guiding significance for mine practical production. |
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