Research On The Inversion Of Tectonic Stress Field And Deformation And Failure Characteristics Of Tunnel Surrounding Rock In Jinfeng Gold Min

In the process of deep mining,complex geological structures induce dynamic disasters,which seriously affect the safety of mining.Based on the Guizhou Provincial Science and Technology Support Plan project,with the Jinfeng Gold Mine as the engineering background,this paper comprehensively utilizes engineering geological survey,physical tests,numerical simulation,and other means to study the stress distribution law of the study area under multiple tectonic stresses,analyzes the after excavation of typical working faces in the research region,the deformation and failure characteristics of the rock surrounding the roadway,and puts forward suggestions for regulating the rock-surrounded roadway’s stability,provides scientific evidence for safe mining and roadway support design.The main research conclusions are as following:（1）The stratigraphic and structural characteristics of the mining region have been methodically established through the research of the geological background of the mining area.,and the structural evolution process has been analyzed.It is concluded that the mining area has experienced the superposition of multiple tectonic movements（Indosinian,Yanshan,and Himalayan movements）.Through acoustic emission Kaiser effect paleotectonic stress testing,the main tectonic movement stages and corresponding paleotectonic stress intensity of the mining area were determined:103.92～110.28MPa during the Indosinian period;59.71～68.35MPa during the Yanshan period;During the Himalayan period,it was 23.44-26.16MPa.Field investigation was conducted on the 30m level of the excavated roadway in the mining area,and it was found that tectonic stress has a significant impact on the deformation and destruction of the roadway surrounding rock,resulting in instability and destruction of the roadway surrounding rock（wall spalling,caving,and floor heave）.（2）Through micro CT scanning,digital image processing（DIP）,and numerical simulation test system(RFPA^3D),three-dimensional models of different pre fractured sandstone based on real mesostructure were reconstructed,and uniaxial compression numerical tests were conducted to investigate the formation of joints and fissures in rock affects the stability of the rock mass and road.According to the findings,sandstone samples’failure modes can be classified into three categories:tensile failure,composite tensile shear failure,and shear failure at the joint surface;The elastic modulus and compressive strength have obvious anisotropy;Joints have significant inducing and controlling effects on the initiation,development,and destruction of sandstone cracks;The fractal dimension damage value can reveal the damage evolution process of sandstone.The research shows that the meso heterogeneity of rock has a certain degree of impact on the macro fracture of rock mass and roadway.（3）A three-dimensional geological model was created using the software GOCAD,and Midas software was used to inverse the tectonic stress field of the Himalayan period within the mining area.The area’s maximum and minimum primary stresses as well as the shear stresses were examined,revealing the rock strata’s laws for stress distribution under various tectonic processes.The findings indicate that the mining area’s maximum horizontal primary stress is 27.32～30.58MPa,which fluctuates greatly near the fault and less in other areas;The maximum shear stress is between 11.52 and 16.24MPa,with small shear stress and small variation.（4）In order to model the excavation of a 30 m horizontal roadway under tectonic stress,the discrete element program 3DEC was employed.The findings demonstrate that the floor heave is not readily apparent,and the roadway top and both sides have significant deformation;The surrounding rock around the fault is severely damaged,with a maximum displacement of 1.25 m.Based on the existing support methods in the mining area,suggestions are proposed for controlling the stability of surrounding rock in the area where the stratum meets the stratum and in the fault area.In the area where the stratum meets the stratum,the bolt spacing can be appropriately reduced,the bolt parameters can be replaced,and steel pipe concrete supports can be installed in the fault area to increase the support strength.