Stability Analysis Of Surrounding Rock And Study On The Construction Method For Dongcheng NO.1 Neighborhood Tunnel

With the rapid growth of China's economy,the demand for traffic development is also increasing,the construction of the tunnel with it,and presents a number of highway tunnel rapid growth trend,form emerge in endlessly.The complicated geological conditions of mountainous area--Southwest China,due to the limitation of the special geologic and topographic conditions,bridge and tunnel link,double line tunnel spacing are always cannot meet the specification requirements of ordinary separated tunnel.So,it must be designed to be unique layout type,like neighborhood tunnel or adopt multi-arch tunnel etc.Neighborhood tunnel which has many advantages,such as improving the capacity of the highway and overcoming the limitation of the engineering site.But it's layout type also brings a series of problem like huge interaction effect of this tunnel construction,high security risk,great difficulty in construction.Therefore,combination of monitoring measurement,numerical simulation and theoretical analysis is adopted in this paper aimed at Zunyi Dongcheng No.1 Tunnel Engineering to study the stability of surrounding rock of neighborhood tunnel and construction scheme in order to optimize the design and guide construction.First,bases on the existing research results,from the angle of rock mechanics analysis deformation and failure mechanism after the excavation of tunnel surrounding rock,discusses the calculation method of single hole tunnel with neighborhood tunnel surrounding rock pressure,clears after the excavation of tunnel surrounding rock stress,cleares the surrounding rock stress after the excavation of tunnel.And the classification of surrounding rock pressure,the method of judging the stability of surrounding rock are summarized.Combines with the engineering practice,on the basis of highway tunnel surrounding rock stability classification standard,it can be concluded that the stability of Dongcheng No.1 tunnel surrounding rock is stability and instability.Second,throughes the monitoring of surrounding rock of tunnel construction site,and takes mathematical regression analysis for the collected raw data,usse Origin drawing software to carry on exponential function and logarithmic function,hyperbolic function curve fitting for monitoring data.Selects optimal function forecast the time needed and the final settlement of section vault subsidence and clearance convergence of different level surrounding rocks.The results show that the exponential function equation can reveal the deformation law of surrounding rock well and the right tunnel construction of Small clear distance tunnel has a significant effect on the left tunnel.Third,in order to obtain the reasonable values of the neighborhood tunnel,discusses the judgment criterion of the reasonable distance of the neighborhood tunnel.Uses large finite element analysis software MIDAS-GTS create 3D model,and the simulation analysis is carried out under the condition of different net distance.By comparing the mechanical and deformation characteristics of the middle rock column under different net distance conditions,gets the reasonable net distance of the neighborhood tunnel under the condition of level IV surrounding rock.Finally,in order to obtain the best construction method of neighborhood tunnel,by numerical simulation to master force deformation condition of neighborhood tunnel in full section method,up and down steps method and single side wall pilot tunnel method of rock and tunnel supporting structure,and unite simulation results to carry out an analogy of economic analysis with different methods.It turns out that in the surrounding rock conditions of level ?,full face method does not apply to IV rock construction,up and down steps method will get more economic benefit than single side drift method.Thus,the optimal construction method is up and down steps method.