Study On Stability And Support Measures Of Jointed Surrounding Rock In High Ground Stress Hydraulic Tunnel

The primary task of underground space development and utilization is the stability analysis of the surrounding rock of underground engineering.Due to the complexity of geological structure and the development of joints and fissures in rock mass,there are great uncertainties and challenges in the simulation analysis.It is significant to study the stability and support measures of jointed rock mass in deep buried hydraulic tunnel with high in-situ stress.Deep high in-situ stress combining with Xinjiang diversion tunnel,field monitoring and numerical simulation with the combination of means,respectively of high ground stress of joint rock mass stability,the tunnel after excavation of the lining structure of mechanical characteristics and joint characteristics of deep high ground stress diversion tunnel surrounding rock stability influence study,and put forward more appropriate support measures,the main research work and conclusions are as follows:(1)During the excavation of deep-buried tunnels,high ground stress and the development of structural planes are key issues to control the stability of the surrounding rock of the cavern.According to on-site monitoring,the measured maximum principal stress is in the range of 12.40～12.90 MPa.The meta-software 3DEC simulates the changes in the stress field,plastic zone and displacement field of the surrounding rock.The results show that a plastic zone of 0～2.10 m appears near the cavern,the maximum displacement value is 25.10 mm,the maximum compressive stress is 13.20 MPa.The plastic zone of the side wall and the arch bottom of the cavern,the displacement value is large,and there is a local small-scale tensile stress.Since the most unfavorable structural surface is selected for the simulation,the simulation result is slightly larger than the actual measurement result.The purpose is to better guarantee the safety of the cavern.The simulation result is more consistent with the actual measurement result.(2)With a project in Xinjiang as the research background,the experimental study was carried out in the section of the tunnel with developed joints and fissures.Due to the developed joints and fissures and high ground stress,the deformation of the test tunnel after excavation was mainly concentrated in51.37～66.73 mm,the tunnel surrounding area is mainly shear failure,and the maximum plastic zone is about 3.90 m.It is necessary to support the tunnel to ensure the stability of the cavern.Considering the impact of the support timing on the support effect,two extreme times are simulated,namely excavation after the deformation is stabilized,lining is carried out and immediately after excavation.The results show that after the excavation,the cavern is normally lined after the deformation is stabilized.The maximum deformation is reduced by 51.67 %,the maximum horizontal displacement is reduced by 46.87 %,and the maximum vertical displacement is reduced by 41.02 %.The lining is carried out immediately after the excavation,and the surrounding rock the deformation is reduced by 58.94 %～76.31 % compared with the deformation of the support after the excavation is stable.(3)The support immediately after the excavation is more conducive to the stability of the cavern and provides reference value for the construction of the project.Therefore,the construction is carried out by the method of excavation and support.Under different support opportunities,the stress of the surrounding rock in the shallow part of the tunnel has been improved,and the stability of the rock mass around the tunnel is guaranteed.However,under the conditions of high ground stress and joint development,the lining structure is difficult to maintain long-term stability,and the lining structure is damaged due to large tensile stress,so secondary support is required.After the secondary support,the maximum tensile stress of the lining structure is 0.89 MPa,which is less than the tensile strength of concrete.After meeting the requirements and performing secondary support with on-site monitoring,the maximum tensile stress of the lining structure is 0.90 MPa,which is relatively consistent.The research results provide a reference for engineering practice.(4)Considering the joint characteristics influence deep high geostress diversion tunnel stability,combined with the engineering practice,this article adopts the numerical simulation to study the joint Angle of high geostress diversion tunnel for deep hole weeks the effect on the stability of the rock mass,the simulation results show that when the joint Angle is small,the deformation is concentrated in the lateral wall and the arch waist place,along with the increase of joint Angle,hole weeks as a trend of increase with the decrease of the first rock mass displacement and joint Angle of 0 °,displacement is concentrated near the side wall and the arch waist,the maximal displacement of 30.60 mm,when compared to other Angle displacement value is the largest,the most unfavorable to rock mass stability.