The Research For Large Cross-section Loess Tunnel Excavation Deformation Monitoring And Analysis Of The Construction Process

Due to our country promotes a variety of strategies recent years,the rapid development of the transportation in western provinces,more and more highways and railways will cross the loess regions.The Loess tunnel design and construction in our country are dominated by Engineering Analogy Method,rather than highly mature design and construction system.Based on Tang Jiayuan loess tunnel,this paper studies the surrounding rock change law and pressure distribution law of loess tunnel,mainly using the combined measures of the field monitoring quantity control,theoretical calculation for surrounding rock pressure and numerical simulation method,to provide the reference for the similar large cross-section loess tunnel design and construction work.The main research content is as follows:?.Four loess tunnel construction methods are introduced,Respectively: Center Diaphragm(CD method),Both side draft method,Center Cross Diaphragm(CRD method),Three Steps Method.And the four methods are compared and analyzed.?.According to the data measured on site,the deformation of loess tunnel surrounding rock generally experiences three stages "dramatic change-slow change-basically stable".Before closing the invert arch,the deformation amount accounts for over 90% of the total,so basically stable stage occurs after completion of the invert arch.And in accordance with the Technical Specification for Highway Tunnel Construction: the optimal time for secondary lining construction is the 18 th day after tunnel excavation.?.Adopting the existing six surrounding rock pressure calculation method and seven judgement method for tunnel deep and shallow bury calculates that the calculation result of Terzaghi Theory well coincides the test result.So the Terzaghi Theory is thus recommended to be the calculation theory of Tang Jiayuan large cross-section loess tunnel's surrounding rock,and the recommended dividing standard of Tang Jiayuan loess tunnel deep and shallow bury is 47 m.?.By means of the numerical simulation,studying the surrounding rock change law,pressure distribution law and plastic zone distribution law of Center Diaphragm(CD method),Both side draft method and Three Steps Method under the same supporting design parameters concludes that: Adopting Both side draft method in Tang Jiayuan tunnel construction is able to control the deformation of the surrounding rock,maintain the surrounding rock self-control ability and stability more effectively.