Stability Analysis Of Surrounding Rock Of Tunnel Through Water Enriched Zone And The Optimization On Its Construction Scheme

With the advance of urbanization in our country,an increasing number of mountain tunnels are demanded.Some deep neighborhood tunnels have to be built due to the limitation of terrain and traffic line selection during highway constructions in mountainous areas.Fault zone is a common adverse geological condition,and improper excavation in such zone likely results in construction incidents because the stability of surrounding rock is diminished due to its low strength and high permeability.In addition,underground water will also impose seepage force on tunnel’s supporting structure during tunnel construction and operation,thus affecting the safety of tunnel structure.Which construction scheme should be adopted to ensure that tunnel can safely and efficiently go through water enriched fault zone,and effectively control the discharge of underground water for the purpose of safeguarding ecological balance is a key problem to be solved in the design and construction of deep neighborhood tunnel.Aimed at this problem,the paper is to research the neighborhood tunnel through water enriched fault zone by taking DaPingwei Tunnel of Cangnan County,Zhejiang Province as the engineering background,investigating the construction site,collecting relevant information,consulting related literature,and by means of numerical simulation analysis.Main research contents are as follow:(1)The characteristics and classification of the neighborhood tunnel and the key point of construction were summarized in details.DaPingwei Tunnel’s engineering situation and the hydrogeological condition of the tunnel through water enriched fault zone were presented.(2)The optimum construction scheme of tunnel through fault zone was obtained by simulating the construction of tunnel through fault zone with software Flac3 D to compare surrounding rock’s vertical displacement,middle rocky column’s horizontal displacement,stress distribution and surrounding rock’s plastic zone distribution under different construction schemes,without considering the seepage effect of underground water.(3)The theoretical knowledge about rock mass structure and rock seepage were summarized;the seepage field and stress field of fluid-solid coupling were deduced through a series of calculations;the characteristics of different seepage models of fractured rock mass were introduced.(4)On the basis of the above research results,and according to the numerical simulation of tunnel through water enriched fault zone by virtue of fluid-solid coupling theory,this paper was aimed at comparing the stability of surrounding rock of tunnel through water enriched fault zones with and without seepage,and revealing the necessity of considering underground water’s seepage effect during the excavation of tunnel through water enriched fault zone.Moreover,the tunnel left holes was taken as an example to compare the advantages and disadvantages of different waterproof and drainage schemes from aspects of water pressure upon lining,secondary lining’s veridical displacement and tunnel drainage,so as to design the best waterproof and drainage scheme.