| When a mountain tunnel crosses a gully,there are many unfavorable factors,such as broken surrounding rock,shallow buried tunnel,uneven stratum and bias pressure,which often lead to tunnel collapse,face collapse,large deformation and other safety accidents after tunnel excavation,and even cause surface collapse and other damage,thus threatening the safety of the constructors and affecting the construction progress.As a kind of bad geology,gully has adverse effects on tunnel excavation.Taking Wangguanhe Tunnel as the research background,combined with the actual situation of the bad geological section,the stability of surrounding rock of the tunnel in the bad geological section and the stability of the tunnel under different disposal measures are studied by numerical simulation.The different schemes are further optimized and analyzed and applied to practical projects.The rationality of the construction scheme of the bad geological section is verified by monitoring and measuring data on site.The main research contents are as follows:(1)Combining with the original data of Wangguanhe tunnel design and investigation,the comprehensive geological prediction system combining shortrange geological prediction by GPR and distance prediction by TSP method is adopted to analyze and determine the surrounding rock condition of unfavorable geological section.(2)The mechanical characteristics of tunnel engineering surrounding rock,deformation mechanism and control measures of tunnel surrounding rock are analyzed.Combined with the theoretical analysis of tunnel supporting structure in shallow fractured rock mass and related supporting principles,the supporting system of tunnel construction is established to determine the treatment measures of tunnel in bad geological section.(3)Based on the actual situation of bad geology in the gully section of Wangguanhe Tunnel,the influence of surface gully on the stability of tunnel surrounding rock is studied by theoretical analysis and numerical simulation.The theoretical analysis shows that the geological condition is poor when the tunnel passes through the bad geologic section,and the excavation disturbance is easy to cause collapse,which is disadvantageous to the stability of tunnel surrounding rock.A three-dimensional numerical analysis model is established by using MIDAS/GTS NX.Based on the analysis of the distribution characteristics of displacement,stress and plastic zone of surrounding rock in bad geological section,the influence of different burial depth on the deformation of surrounding rock in the presence of gullies is revealed.The results show that the existence of gullies aggravates the instability of surrounding rock.(4)In view of the topographic and geological conditions of the unfavorable geological section of Wangguanhe Tunnel,the supporting mechanism and arrangement of three grouting reinforcement schemes,i.e.advance small conduit method,pipe shed method and surface grouting,are elaborated in detail.The stability of surrounding rock of the tunnel under three disposal measures is studied and optimized by using finite element software.The results show that under the condition of grouting reinforcement,the stability of surrounding rock is improved,the scope of plastic zone is reduced,and advanced small pipe support is adopted,which is simple to operate,low cost,and the support effect can also meet the design requirements.(5)On the basis of the simulation and statistical results,the on-site inspection of the unfavorable geological section of Wangguanhe Tunnel is carried out,and the feedback information data of on-site monitoring and measurement are regressed and analyzed,and the disposal measures are verified by the actual monitoring method.Through the comparison and analysis of the numerical simulation value and the actual monitoring value,the verification shows that they are in good agreement. |
PDF Full Text Request