Research On Deformation And Failure Characteristics Of Surrounding Rock And Support Optimization In Yongchang Lead-zinc Mine Tunne

With the gradual depletion of mineral resources in the shallow part of metal mines,the move to the deeper part has become a normal trend,and in the process of moving to the deeper part of mining,the deformation control of the roadway surrounding rocks is a major technical problem.In this paper,the 200 m middle section of the 860 pit at the Yongchang mine in Yunnan,the largest burial depth at the present stage,is used as the research object to investigate the deformation and damage of the surrounding rock and the current situation of support.The test results are combined with the relevant results of the ground stress test to analyse the causes of the instability of the surrounding rocks in the deeply buried roadway.Based on the current situation of roadway deformation and support,the 3D finite difference numerical simulation software FLAC3 D is used to simulate and invert the deformation characteristics of the surrounding rock after excavation and the original support method,and based on the instability characteristics of the surrounding rock under the original support method,four optimal support solutions are proposed for the asymmetric deformation of the surrounding rock of the roadway and the obvious bottom bulge based on the anchor spray network support.The optimized support scheme for the roadway is determined,which provides certain experience and reference significance for the field of deep mining and similar geological conditions.The main findings of this paper are as follows:(1)The site investigation found that the support method in the study area is mainly steel arch frame shotcrete and anchor spray network support,the deformation of the surrounding rock of the tunnel in the area is characterised by asymmetric shift in the two gangs,the sinking of the top plate and the obvious bottom drum,the deformation and damage of the surrounding rock is extensive and long-lasting,and it is significantly affected by the distribution of geological structure rock layers and the effect of ground stress;(2)The instability of the surrounding rock in the deeply buried tunnel is mainly determined by the physical and mechanical properties of the surrounding rock itself,the support effect,the boundary conditions of the support system and the disturbance during the excavation and excavation of the tunnel,etc.The influence elements are analysed and evaluated by mathematical methods,and the burial depth of the tunnel,the influence of groundwater,the tectonic stress,the structure surface production and the spatial combination are the main causes.(2)The main factors are the quality of support application,the time of application and the type of support structure,and the mechanism of rock instability should be comprehensively evaluated and studied;(3)Through the identification of the mineral composition of the surrounding rock and the loosening circle test,combined with the results of the ground stress test,it is found that the main reasons for the instability of the surrounding rock of the roadway are:(1)the surrounding rock of the roadway itself is of low strength,the laminae are developed,and the area of the weak interlayer of the surrounding rock is extensive;(2)the surrounding rock contains a high content of clay minerals,which is easily affected by groundwater and weathering,resulting in weakening of the strength;(3)the study area is under high ground stress,and the direction of the roadway layout is perpendicular to the maximum(3)the study area is under high ground stress,and the direction of the tunnel layout is perpendicular to the maximum stress,which is not conducive to the stability of the tunnel;(4)the existing support methods and related parameters are unreasonable;(4)Using FLAC3 D software to simulate and invert the deformation and damage characteristics of the tunnel surrounding rock,it is found that:(1)the deformation of the tunnel surrounding rock is large without support,the convergence of the two gangs,the sinking of the roof plate and the bottom drum are large,the bottom drum deformation of the tunnel has obvious rheological effect,and the whole section of the tunnel will gradually disappear;(2)the steel arch spray mixed support and anchor spray network support have some control on the roof plate and the two gangs of the tunnel,but the tunnel as a whole The former has a better control effect on the deformation of the top and bottom of the roadway,while the control effect on the surrounding rocks of the two gangs is weak;(3)the weakest part of the support is the bottom of the roadway,followed by the left gang,the top of the arch and the right gang of the roadway;(5)Four optimized support schemes are proposed,and the optimized support scheme of anchor spray network + anti-bottom arch is determined through simulating and analyzing the effect of the four schemes on the control of the surrounding rock,which provides a certain basis for the analysis of the reasonableness of the design of the support method of deep mining in the mine.