关键词: 房柱法, 围岩稳定性, 承载机理, 矿柱, 矿房跨度, 数值分析, 戈塘金矿

Abstract:

The room and pillar method is one of the mining methods with high labor productivity, which is widely used in small metal mines.Getang gold mine is located in Anlong County，southwest Guizhou Province，with complex geological conditions.The gold ore body directly covers the undulating paleo-karst erosion surface of the Maokou Formation，and its thickness varies from 0.3 m to 76.0 m.The lithology of the top and bottom of the ore body is complex.In order to design the parameters of underground stope scientifically，analyze the failure mechanism of the roof of the goaf and the bearing mechanism of the pillar，and guide the safe production of the mine，this paper used the theoretical calculation combined with the numerical simulation method to reasonably select the stope parameters and carry out the numerical analysis of the surrounding rock stability of the stope.Through the calculation of the mining span theory，the span of the mine is ≤10 m and the recommended pillar size is 3 m×3 m.Due to the large variation of the thickness of the orebody，the stability of the surrounding rock of the stope should be analyzed under different mine height conditions.In this paper, a numerical model of pillar width of 0.300,0.375 and 0.500 was established by using the finite element Phase 2, and the stability of the surrounding rock in the stope was analyzed by numerical simulation.The simulation results show that when the pillar width-to-depth ratio is 0.300，0.375，0.500，the average stress levels of the floor in the goaf are 12.78，8.04，7.03 MPa.The average stress levels of the rock mass are 19.02，13.03，13.06 MPa.The average stress levels of the roof of the goaf are 10.73，7.20，6.04 MPa；The average stress levels inside the pillar are 28.07，18.62，18.54 MPa；The average displacements near the floor of the goaf are 0.83，0.67，0.62 mm；The average displacement near the rock dam is 2.52，1.27，0.95 mm；The average displacement near the top plate is 8.53，4.73，4.45 mm(maximum displacement is 9.80，5.55，5.27 mm)；The average internal displacement of the pillar are 2.05，0.93，0.68 mm，respectively.According to the com-prehensive analysis，we can conclude that:(1)After the mining，the stress concentration inside the pillar is affected by the supporting pressure，and the floor，rock and roof of the goaf are the stress reduction area；the stress level inside the pillar is the highest near the boundary of the goaf.The stress level inside the rock core is second，and the stress level of the floor and roof of the goaf is the lowest.(2)After the mining，the maximum displacement occurs in the vicinity of the roof of the goaf due to the occurrence of the fracture zone and the plastic zone and the pressure of the overburden. Due to the conduction of support pressure，the displacement value of the pillar from top to bottom is gradually reduced.(3)The maximum stress value and maximum displacement inside the pillar appear at the top of the pillar；The pillar width-to-depth ratio has a certain influence to the stability of the surrounding rock of the stope.With the increase of width-to-depth ratio，the average stress level and average displacement near the boundary of the goaf are reduced，the stress concentration in the pillar is alleviated，and the deformation is reduced. In the process of mining，the size of the pillar should be increased appropriately at the location where the depth of the ore body is large and the thickness of the ore body is large.Keeping the width-to-depth ratio of the pillar at about 0.500 can better maintain the stability of the stope.

Key words: chamber and pillar method, stability of surrounding rock, bearing mechanism, pillar, the span of mineroom, numerical analysis, Getang gold mine