| With the rapid development of China’s economy and society,national infrastructure projects have been widely implemented.In the construction of subway,tunnel,water conservancy and hydropower,mining and other major projects,the surrounding rock stability and water inrush disasters in the process of rock mass excavation are involved.Sanshandao Gold Mine is a hard rock metal mine adjacent to coastal water.The main water conducting structural fracture of the mine is Sanshandao-Sanyuan F3 fault zone.The deformation and failure mechanism of fault bearing rock mass and the evolution mechanism of water flowing under water pressure were studied to realize the early warning and advance support of surrounding rock instability and water inrush in mining,which was of great practical significance to ensure the safe and efficient mining of the mine.This thesis focused on the surrounding rock stability and water inrush in the process of underwater mining with fault fracture zone,taking the jointed rock mass in-915m level tunnel of Sanshandao Gold Mine as the engineering background,using the methods of field investigation,mechanical analysis,laboratory test,theoretical derivation and numerical simulation,the deformation and failure law of surrounding rock mass and the water inrush disaster mechanism of surrounding rock roof were deeply studied,and the stability of surrounding rock with fault and the prevention and control measures of surrounding rock roof water inrush were discussed.The main research conclusions are as follows:(1)The survey line method was used to conduct field survey and measurement analysis of the surrounding rock in the-915 middle section of the Xishan mining area of Sanshandao Gold Mine.The results showed that the surrounding rock mixed granite group in the area had well-developed joints,which belong to broken and extremely broken rock masses with poor stability.Through the analysis of joint occurrence,it was concluded that the dominant structural surface of the middle joint is 295°∠85°,the roughness of the joint is mostly general rough(GR),and the joint opening is concentrated in 0.25～2.5mm.(2)According to the triaxial compression test results of jointed rock mass specimens with different joint inclination angles,different joint penetration rates and different joint types under water pressure,the results showed that the number of joints and the joint penetration rate have a strong weakening effect on the mechanical properties of jointed rock masses,while the inclination angle of joints played a controlling effect on the mechanical parameters’ change of jointed rock mass specimens.By analyzing the relationship between the acoustic emission characteristics and the strength changes of different specimens,it was concluded that the acoustic emission energy changed within a larger value range when the specimens reached the peak stress,and the energy suddenly increased before the specimen reaches the peak stress.Therefore,the large sudden change of the acoustic emission energy before the deformation and failure of the jointed rock mass specimen can be used as the precursor information for the deformation and failure of the specimens.(3)By analyzing the relationship between the energy transformation process and stress change in the deformation and failure process of jointed rock mass specimens,the energy evolution law and damage failure energy mechanism of jointed rock mass specimens were obtained.Through the analysis of the relationship between energy transformation or energy dissipation and stress change in the process of deformation and failure of jointed rock mass specimens,it is concluded that the abrupt change of the elastic energy consumption ratio near the peak strength of the specimen can be regarded as the criterion of strength failure.According to the fracture mechanics theory,the stress intensity factor of joint tip under water pressure was obtained.Considering the joint damage,load damage and the influence of water pressure on the damage of jointed rock mass,the damage constitutive model was established,and derived the stress intensity factor criterion for strength failure.The water pressure promoted the damage evolution process of jointed rock mass specimens and accelerated the strength failure of jointed rock mass specimens.(4)Through the analysis of the fracture evolution process at the joint tip when the jointed rock masses were deformed and destroyed under water pressure,the failure mode of the jointed rock mass specimens,and the failure mode of the jointed rock specimens were obtained.The joint inclination angle had an obvious guiding effect on the expansion direction of the main fractures,and it was also the main controlling factor of the deformation and failure type of the jointed rock mass specimens.Through the monitoring of the water flow change during the failure process of the specimens,the relationship between the strength change and the water flow of the specimens with different joint inclination angles and different joint types can be obtained,and the evolution law of the permeability coefficient of the jointed rock mass specimens can be analyzed.Since the joint inclination angle had a great influence on the initiation and evolution of the cracks of the specimens,the weakening effect of the water pressure on the strength of the specimens was mainly through the water channel generated by the internal cracks of the specimens,so the permeability coefficient of the jointed rock mass specimens had a great correlation with the joint inclination angle.By comparing and analyzing the failure modes of jointed rock samples with different joint fillings,it can be concluded that the filling of cement slurry can not only improve the integrity of the test pieces,but also effectively control the shear cracks of jointed rock specimens due to joint dip angle,and effectively control the shear failure of jointed rock specimens.(5)Based on the COMSOL Multiphysics software platform developed by COMSOL(Sweden),a roadway excavation models for underwater mining of faulted rock masses were established,and the water flow characteristics of the model under different working conditions and the stress change law of surrounding rock under fluid-solid coupling are analyzed and studied.Drilling holes in the roadway for grouting reinforcement in the face of the fault,analyzing and studying the seepage and stress distribution after grouting reinforcement in the fractured zone of the fault,which can well verify the effectiveness of grouting reinforcement for improving the integrity of the surrounding rock and obstructing the water channel.After research,it is concluded that for the jointed surrounding rock near the fault fracture zone,it is necessary to adopt local reinforced bolt and shotcrete support measures on the basis of grouting reinforcement to improve the stability of the surrounding rock and effectively prevent water inrush accidents.(6)Taking the jointed rock masses of the-915 middle section of the Xishan mining area of Sanshandao Gold Mine as the research object,a three-dimensional roadway model was established by using FLAC3D(Fast Lagrangian Analysis of Continua 3-Dimensional model)to reflect on-site mining and tunnel layout engineering.The influence rules of the surrounding rock deformation and stress distribution caused by the surrounding rock with bolt mesh shotcrete support,bolt+U-shaped steel support or without support were compared and analyzed,and the support effects of different support schemes were obtained.The method of grouting reinforcement+local reinforced bolt-mesh shotcrete support was put forward,and the supporting effects of the bolt-mesh reinforcement and grouting reinforcement+local reinforcement bolt-mesh shotcrete support scheme were compared and analyzed.The influence of different joint inclination angles on the surrounding rock stability of the roadway was analyzed in depth.It is concluded that grouting reinforcement+local reinforcement of bolt-net shotcrete support had a significant effect on improving the support effect.The maximum horizontal displacement and maximum vertical displacement of the surrounding rock of the roadway were reduced by 49.64%and 59.75%,respectively.Therefore,for the surrounding rock of the jointed rock mass roadway with a high degree of fragmentation,it was recommended to adopt the "grouting reinforcement+local strengthening of bolt-net shotcrete support" program,which not only improved the work efficiency but also effectively guaranteed the safe and efficient mining of the mine. |
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