| Building Lanzhou-Chongqing railway is the key supportting infrastructure project ofChina, this paper takes Muzhailing tunnel in Lanzhou-Chongqing railway as the researchbackground, combined with the construction method and monitoring measurement project ofthe tunnel, numerical simulation method is used to study the control technology of largedeformation of high ground stress soft rock.Aiming at the problems of arch deformation and secondary lining cracks caused by largedeformation in construction site of Muzhailing tunnel, the following researches are carriedout:(1) Based on the engineering geological conditions of Muzhailing tunnel, combined withthe results of laboratory soil test, material parameters of the model are selected; typicalsection is selected in construction site of tunnel, deformation of the surrounding rock ismonitored after the excavation of section, the data is analyzed, and the changing law of highground stress soft rock of large deformation is required.(2) By using the finite element software MIDAS-GTS to simulate three step constructionmethod of Muzhailing tunnel, deformation of surrounding rock is caused with the excavationstep and the change of relative position of tunnel face in the process of tunnel excavation, andthe ratio of surrounding rock deformation to the total deformation is analyzed, technicalmeasures to control large deformation is required, the range of plastic zone of the tunnel, theinfluence of side pressure coefficient on the deformation and stress of supporting structure arefutherly studied to put forward the optimization measures of supporting method.(3) Through the simulation of construction of secondary lining with and without big archfoot, the deformation and mechanic property of tunnel surrounding rock are analyzed undertwo cases, rationality and validity of improved grouting technology of secondary lining areproven, optimization measure of construction of secondary lining is proposed.(4) Through the numerical analysis of CRD construction process of Muzhailing tunnel,coMPared with mechanic and deformation property of surrounding rock of three stepconstruction method, constructive suggestions to choose the construction method ofMuzhailing tunnel is put forward.The results of the paper are as follows:(1) The rationality of in-site construction method and supporting form are verifiedthrough regression analysis of the monitoring data of Muzhailing tunnel, reasonable time toapply secondary lining can be accurately determined, powerful basis is provided to timelyadjust the supporting structure when necessary. (2) Results of numerical simulation show that the beginning deformation in front of theexcavation face of convergence curve accounts for32.8%of total deformation, deformationof tunnel face accounts for54.9%of total deformation, deformation behind the tunnelaccounts for12.3%of total deformation, strengthening the advanced support in theconstruction of soft rock tunnel has an important effect on controlling large deformation, socontrolling technology of large deformation of high ground stress soft rock tunnel is putforward.(3) Through the simulation of secondary lining with and without big arch foot, thecalculation results show that the vault settlement of surrounding rock of secondary lining withbig arch foot is36%smaller than that without big arch foot, horizontal convergence ofsurrounding rock of secondary lining with big arch foot is38%smaller than that without bigarch foot, which shows that coMPared with secondary lining without big arch foot, secondarylining with big arch foot can obviously reduce the vault settlement and horizontalconvergence value.(4) Finite element software is used to conduct numerical simulation on CRD method ofMuzhailing tunnel, the calculation results show that: coMPared with three step method, byusing CRD construction method, vault settlement is reduced by10%, horizontal convergenceis reduced by12%, changing curve of stress is smoother, and variation range is smaller, thesupporting structure is more reasonable.In summary, combined with the field monitoring data of Muzhailing tunnel, lots ofnumerical simulation is undertaken, rationality of the field construction method is validated,and more reasonable control technology of large deformation and optimization measures areput forward, which provides effective suggestions to the design and construction of similartunnels like Muzhailing tunnel, and has produced some good economic benefit and socialbenefit. |
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