| Mengnuo lead-zinc mine is an important large pb-zn deposit in Baoshan metallogenic belt in Sanjiang area of China.The mining area is mainly located in the east wing of the Mengnuo second syncline,which is located in the north-south direction of the Yaoguan-Jiufang compound syncline Most of the ore bodies in the mining area occur in the crystalline limestone of the upper Renheqiao formation of the middle silurian system controlled by the north-south interlayer longitudinal fault.The exposed strata of the mining area mainly include the Cambrian Gongyang River Group,the Ordovician System,the Lower Silurian Xiarenheqiao Formation of the Silurian System,the upper and lower sections of the Shangrenheqiao Formation of the Silurian System,the Lichaiba Formation of the Silurian Upper System,the Devonian Lower Xiangyangsi Formation,the Devonian Middle Heyuanzhai Formation,the Triassic Middle System,the Jurassic Middle Mengga Group,and the Quaternary System.The tectonic development of the mining area is dominated by the compressive and torsional faults to the north and west of the fault,the extensional faults to the east and west of the fault,and the bedding fault.The shear joints near the north-south direction and the north-west-southeast direction are the main joints,and some of them develop the east-west tension joints.Folds are mainly small recumbent folds,crumple and traction structures near faults.The mining area began large-scale mining in 1958 and developed from the initial surface mining to deep underground mining.At present,the mining depth has reached 660 m below the surface.With the deep underground mining,the tunnel inevitably passes through the structural development area.The excavation of the tunnel disturbed the surrounding rock mass and destroyed the structure of the original rock.In this paper,the mining area in 860 200-550 midway through all the pit,as well as 948 and 795 pit pit part middle system on the basis of field geological work,analyzed structure characteristics of the mining area,the selection of main mining area caused by construction of the tunnel surrounding rock instability,selected a reasonable parameter model was established based on the discrete element method and finit e element method to study the structural development zone damage rule of the tunnel,analysis the different structure of tunnel surrounding rock stability influence factors.The following conclusions are obtained: 1.The main structure causing the instability of the surrounding rock in the mining area is fault and joint.2.The instability of the surrounding rock of the tunnel in the shear joint area mainly occurs at the arch top,while the instability of the arch shoulder and two sides of the tunnel in the tensile joint area is easy to occur.3.Influence of mechanical properties of faults on surrounding rocks of tunnels: bedding fault > tensile fault > compression-torsional fault.The larger the fault width,the greater the influence on the surrounding roc k.The greater the fault dip Angle is,the greater the influence on the stability of surrounding rock will be.4.The mine tunnel is stable in the area where faults are developed in the nw direction of the mining area;The tunnel is unstable in the area where the north-south fault and the east-west fault developed.The tunnel is very unstable in the zone of bedding fault development. |
