| Due to the engineering nature of shallow buried biased soft rock tunnels,tunnel construction often has a variety of diseases,such as instability of surrounding rock,collapse,excessive ground subsidence and even cracks.In order to reduce construction risks,ensure construction progress,and save engineering costs,relying on the combination of on-site investigation,theoretical analysis,numerical simulation,field test and field application verification,relying on the construction of the Zhangjiajie-Jishou-Huaihua Railway Guantian Tunnel Project.Aiming at the deformation characteristics of shallow buried bias soft rock tunnel construction,the construction deformation control method of shallow buried bias soft rock tunnel and the construction deformation control technology of shallow buried bias soft rock tunnel,the following conclusions are obtained:(1)Through the theoretical analysis and literature analysis,the basic characteristics of the expansive surrounding rock are studied,and the adverse effects of the expansive surrounding rock on the tunnel construction are summarized.The expansion and contraction mechanism of the expansive surrounding rock is analyzed from the aspects of internal and external factors.The constitutive relation formula of expansive surrounding rock with time effect and no time effect is derived.The causes and classification of the bias phenomenon of shallow buried bias soft rock tunnel are studied.The influence of shallow buried bias soft rock tunnel is analyzed.The main factors of the bias phenomenon are studied.The adverse effects of surrounding rock bias on shallow-buried biased soft rock tunnels are studied,which lays a theoretical foundation for studying the control method and technology of shallow-buried biased soft rock tunnel expansion deformation.(2)Based on field test and numerical simulation,based on the deformation characteristics of surrounding rock of shallow buried bias soft rock tunnel,comparative analysis was carried out from various aspects such as construction technology,deformation control effect,construction safety,construction convenience and construction progress.The optimized temporary arch step method has determined the shallow buried bias soft rock tunnel with the "three-step reserved core soil method for the expansive soft rock section,the optimized temporary arch step method for the fault fracture zone and the severely biased section".Construction deformation control method.(3)Through the numerical simulation and field test,the surrounding rock deformation control concept of "rigid-flexible combination,enhanced support integrity,enhanced advance support,controllable grouting reinforcement" is proposed,and the shallow buried bias is compared and analyzed.The different methods and parameters of the advance pre-support,steel frame support and grouting reinforcement of the expansive soft rock tunnel,the new technology of "alternating" rigid-flexible arch support and the new technology of "shelving"advanced pre-supporting are proposed.A series of key new technologies,such as composite control grouting reinforcement technology,have determined the construction deformation control technology of shallow buried bias soft rock tunnel.(4)Through monitoring measurement and field test,combined with the actual situation of Guantian tunnel site engineering,the deformation characteristics and construction deformation control measures of Guantian tunnel were deeply studied,and the monitoring and measurement data of Guantian tunnel site were detailed.The different support measures,the deformation displacement of the surrounding rock before and after the optimization design,the support pressure and the stress were compared and analyzed.The effectiveness of the construction method and technology of the shallow-buried biased soft rock tunnel deformation control was tested,in order to modify the design and construction parameters.Provides a technical basis. |
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