Study On The Mechanical Effect Of The New Road To Invisible Bridge Covered Excavation Method And Its Impact On Existing Track Safety

With the development of society,the improvement of urbanization and the increase of urban population,the pressure brought by traffic is more and more obvious.However,the development of urbanization cannot be restrained by traffic pressure.The underground traffic corresponding to the traditional ground traffic is a new way to relieve the traffic pressure.Covered excavation is widely used in urban underground engineering construction.In mountainous cities with rugged terrain,road network is complex.In traditional covered excavation,the utilization rate of pavement structure is low.It has a great impact on traffic.Taking Chongqing Railway Sigongli Station as an example,based on reversed construction method,this paper presents a new type of covered excavation called road to invisible bridge covered excavation.The new method is similar to the construction of an invisible bridge,which is different from the general method of cover excavation.It is a mixed application of cover excavation method and road modification bridge.In this paper,the special mountainous city terrain,combined with the specific complex construction conditions,through field investigation,theoretical analysis,engineering monitoring,numerical simulation and other ways to do the following research.(1)Summarizing the advantages and disadvantages of the traditional cover excavation method,combined it with the technology of road reform bridge to form a new type of cover excavation method with invisible bridge.The road to invisible bridge covered excavation is suitable for mountain city construction.It is close to the situation where the construction roads are high and cannot be widened.This method combines the road to bridge and the cover excavation method,avoiding the need for temporary bridge construction due to the topography,shortening the construction time and reducing the project cost.The middle pile is used as a permanent support structure,which reduces the amount of temporary support,improves the safety of the construction,reduces the influence on the surrounding environment,and ensures the normal traffic of the main road of the city.(2)Through the numerical simulation method,the mechanical effect on the construction of road to invisible bridge covered excavation method is studied,focusing on the stress situation and the structural deformation of the key node structure in the construction process of the subway station,and the key points should be paid attention to in the construction process through the stress situation of the station structure.Carry on the lateral contrast analysis.The properties of rock and soil mass in the construction site are changed,and the influence of the new cover excavation method on the safety of the station structure under different rock and soil conditions is studied.The effect of new cover excavation method on station structure safety is simulated by simulating different excavation depths.(3)The relationship between the proposed station project and the existing track is analyzed,and the displacement of existing rail bridge pier during the construction of the subway station with the new method of stealth bridge type is calculated.And comparing the numerical simulation value with the monitoring value.(4)Considering the safety of the project and the cost of the project,the reasonable design scheme of the station structure is determined.The parameters of the column diameter of the station,the number of concrete and the thickness of the interlayer plate of the station are optimized,and the most economical and reasonable choice is obtained through the analysis and comparison of the data,so as to improve the quality of the engineering,improve the economic value and shorten the time limit for the work.