Research On Asymmetric Deformation Mechanism And Prevention Measures Of Sandy Shale Bias Pressure Tunnel

Afected by factors such as topography,geological structure,and on-site construction,the strength and stress distribution of the surrounding rock of the sandy shale biased tunnel are different,and large asymmetric deformation occurs,resulting in the partial destruction of the tunnel support structure.Due to the severe asymmetric deformation and damage of sandy shale biased tunnels,it is difficult to support,and it is difficult for conventional support methods to meet the tunnel safety requirements.Under the regional geological conditions,the area and deformation characteristics of the abnormally deformed sandy shale tunnel often have certain regularity.Based on previous research,this paper combines Zheng Wan high-speed sand shale unsymmetrical deformation and failure engineering case,comprehensively adopts the methods of theoretical analysis,field test,indoor test,numerical simulation and nonlinear analysis.The asymmetric deformation mechanism,calculation theory,influencing factors,deformation grade evaluation and construction support optimization of shale bias tunnels have been studied.The research results of this paper are as follows:(1)Comprehensive analysis of the asymmetric deformation mechanism of sandy shale.The definition and classification of the asymmetric deformation of the biased tunnel,and relying on the Zhengwan high-speed railway sand shale biased tunnel project,carried out tunnel rock and mineral testing and physical and mechanical experimental analysis.Combined with the typical engineering case of the asymmetric deformation and failure of the surrounding rock of the sandy shale biased pressure tunnel,a comprehensive analysis of the asymmetric deformation and failure law of the tunnel is made.Through the analysis of the main control factors,it is concluded that the asymmetric deformation type of the Zhengwan high-speed railway sand shale biased tunnel is the geological tectonic biased type.A new method for obtaining asymmetric deformation data and quantitative grading of sandy shale bias tunnels is proposed.(2)The systematic analysis of the subjective and objective factors affecting the asymmetric deformation of the sandy shale bias tunnel.The effects of the occurrence of shale joints on the asymmetric deformation of sandy shale tunnels are mainly studied.It is concluded that the scale of the asymmetric deformation of the sandy shale biased pressure tunnel is influenced by the combination of joint plane tendency,dip angle and tunnel strike combination.The gray correlation degree and fuzzy Delphi method are used to calculate the objective weight and objective weight of the asymmetric deformation of the sandy shale bias tunnel,and the combined weight of the influence factors is calculated by the combined weighting method.(3)According to the asymmetric deformation influencing factors of sandy shale tunnels,the comprehensive weights are used to simplify the input factors.A simplified BP neural network prediction model for the asymmetric deformation of sandy shale biased tunnels was established by using simplified factors as input parameters and the basic deformation grade and abnormal deformation grade of sandy shale bias tunnels as output parameters.Through the actual engineering verification of Zheng Wan high-speed sandy sand shale bias tunnel,it is concluded that this sandy sand shale bias tunnel asymmetric deformation BP neural network model has high prediction accuracy,which can be applied to the sandy sand shale bias tunnel asymmetric deformation prediction.(4)The numerical simulation method is used to study the asymmetric deformation law of the sandy shale biased tunnel under different excavation and regional support,to explore the reasonable excavation methods and methods for the sandy shale biased asymmetric deformation tunnel Support method.Through numerical simulation analysis,it is concluded that among the five excavation methods studied,the three-step seven-step excavation reserved core soil method(the leading step is on the bias side)is more conducive to the overall stability of the sandy shale bias tunnel.Compared with the longer bolt support,the use of integral grouting and the local optimization of the grouting support depth can effectively control the overall deformation and abnormal degree of deformation of the sandy shale bias tunnel.(5)Use comprehensive geological forecasting methods to obtain engineering geological information in front of the palm face in the excavation of the sandy shale bias tunnel in advance.Establish a prediction model of the surrounding rock quality grade of the sandy shale tunnel,and combine the obtained tunnel engineering geological information to predict the surrounding rock quality grade and complete the initial excavation and optimization of the supporting method.Using the asymmetric deformation prediction model of the sandy shale biased tunnel,the base deformation level and abnormal deformation level are obtained,and the corresponding secondary support optimization measures are taken,and verified by numerical simulation and field engineering.Through comprehensive analysis,it is concluded that the multi-level control method for large deformation proposed in this study has a good control effect on the asymmetric large deformation of sandy shale biased tunnels.