Study On Cooperative Anti-permeability Support Design Of Lining Structure And The Reinforced Surrounding Rock Of Deep Buried Tunnel With High Water Pressure

The rapid construction of deep-buried tunnel is significant for the developing of The Belt and Road and eight vertical and eight horizontal high-speed railway network.TBM(Tunnel Boring Machine)is the technical development direction to achieve the goal of rapid construction.At present,the tunnel support design based on engineering analogy and load structure method could not meet the requirements of both engineering safety and environmental protection.When mechanical tunnelling is carried out under unfavorable geological conditions,problems such as construction delay and support failure often occur.It is necessary and urgent to study and develope the support design of deep-buried tunnel with high water pressure.According to principle of groundwater prevention and permanent support design requirments of deep-buried high water pressure tunnel,the concepts of NATM(New Austrian Tunneling Method)and controlled drainage are considered as the premise of this paper.With the analytical derivation of seepage and stress field,experimental operation of hydraulic characteristics and numerical analysis of reinforced surrounding rock,the cooperative anti-permeability support model including both active reinforcement of surrounding rock and passive lining structure support is proposed,and its calculation method is provided.The main contents and results are as follows:(1)Based on the generalized effective stress principle and nonlinear seepage law,the analytical solutions of seepage field,stress field and displacement field of surrounding rock are derived using the ideal elastic-plastic and elastic brittle plastic material models.The correctness of the derivation is verified by comparing the analytical and numerical results of calculation example.The elastic brittle plastic solution of surrounding rock is used as a method to evaluate the stability of surrounding rock.Taking the radius of brittle plastic zone of surrounding rock and the hydraulic gradient of excavation boundary as indexes,the classification method of surrounding rock of high water pressure tunnel is improved and optimized on the basis of the existing classification method,which reasonably strengthens the connection between the stability analysis theory and the classification method.(2)A experiment device for hydraulic characteristics of surrounding rock is developed,which is suitable for the coring in engineering field.The results of simulate broken rock mass show that:the samples enters into the stage of nonlinear seepage at a certain level of seepage pressure difference,about 0.5MPa;The nonlinear seepage index coefficient is 1.1?1.4,which decreases with the increase of porosity;The effective stress correction coefficient of samples is 0.93-0.95,which decreases with the decrease of porosity.The operability of this device in the engineering field is verified,which provides the experimental method of hydraulic characteristic parameters for surrounding rock stability analysis and subsequent support design.(3)Considering the hydro-mechanical coupling effect,the mechanical model of surrounding rock with grouting reinforcement is established.The influence of nonlinear seepage on the stress state of surrounding rock and tunnel drainage is studied.The nonlinear seepage is benefical to reduce the effective stress of surrounding rock after grouting reinforcement,but not conducive to the control of tunnel drainage.It is suggested that the permeability coefficient of surrounding rock should be reduced as much as possible in the design of grouting reinforment,and then the grouting scope should be expanded appropriately.The influence of grouting reinforcement on the stress state of surrounding rock is studied.The effective radial stress and effective hoop stress of surrounding rock increase after excavation due to the grouting reinforcement,which means that its bearing capacity is improved.And the effective stress of grouted surrounding rock increases with the increase of elastic modulus and internal friction angle,and decreases with the decrease of permeability coefficient.The deformation characteristics of ideal elastic-plastic surrounding rock and elastic brittle plastic surrounding rock under the same load condition are studied.The deformation of elastic brittle plastic surrounding rock is larger,and the reinforcement effect is more obvious.Under the influence of dilatancy effect in the process of excavation and support,its characteristic curve is non monotonic.With the increase of virtual support force,the deformation increases slightly at first,and then decreases rapidly.(4)Based on the equivalent reinforcement model of rock bolt,considering the layout and axial force,the equivalent calculation coefficient is proposed.The effectiveness of the equivalent calculation method for solving mechanical parameters of anchored surrounding rock is verified.Specifically,taking the single anchor reinforcement area as sample,the orthogonal test scheme about layout parameters is designed.Comparing the numerical results of the real model and the equivalent model,the radial displacement of the tunnel excavation boundary in equivalent model are slightly smaller than it in real model,and the difference between them is not more than 3.0%,with an average difference of 1.4%.The density of bolt layout is positively correlated with the effect of bolt support.The influence of bolt radius on bolt supporting effect is the biggest,followed by circumferential spacing and longitudinal spacing.(5)Consisting with the concept of NATM and controlled drainage,the cooperative anti-permeability support model is proposed,which including advance grouting,fast archorage and timely lining.The requirements of drainage limit and external water pressure of lining are met through advance grouting reinforcement.The requirement of stability of surrounding rock is met through the intial support.The requirement of tunnel deformation is met through lining structure.Combined with surrounding rock classification method of high water pressure tunnel,referring to the determination method and quantitative analysis of mechanical parameters of reinforced surrounding rock,the supporting design process and calculation method including grouting,bolt and lining are completed.(6)Under water-rich and broken surrounding rock condition,the cooperative anti-permeability support design is applied to Gaoligongshan TBM tunnel and the design reference is provided.