Construction Mechanical Behavior Analysis Of The Conversion Section From Construction Passage To Subway Station

With the rapid development and acceleration of urbanization,cities have been expanding.Metropolitan center area’s densely populated,and buildings are everywhere,crowded space,traffic congestion and other problems,seriously hampered the further development of economic and society.In order to meet the travel requirements,to achieve the purpose of convenient traffic,people gradually turn their gaze to the construction of urban rail transit.In urban areas traditional method,cut and cover tunneling,is no longer applicable,especially Chongqing,the ground resources are extremely shortage.So we need to build a construction passage for the station tunnel construction.Due to the complexity of conversion section of stress distribution in the process of construction,so the mechanics analysis of conversion section during construction is very important.The overall length of Fengtian road station,in the first stage of Chongqing rail transit loop line,is 209 meters.The station used by building a construction passage for convers to the construction of the main tunnel.Depending on the investigation in the Fengtian road station,this paper analysis the mechanics analysis of conversion section during the construction,to provide the basis and guidance for the practical engineering.And the main research findings are as follows:Firstly,introduced two methods “Climbing method of door type conversion” and “Expansion excavation method of fan type conversion”,analysis the basic principle and the basic construction steps of these construction,and according to the basic steps,3D finite element models are established.Secondly,establish the 3D finite element model of “Expansion excavation method of fan type conversion” by Midas GTS.Analysis the construction mechanics behivior include the displacement and stress variation characteristics of the wall rock and support stress and rock plastic zone after the excavation. It is point out that the joint of construction passage and station tunnel is the weak links of supporting structure,where principal tensile stress exceed tension-compression strength of concrete.Then proved the correctness of numerical simulation of combining with the monitoring data.Thirdly,change the excavation method of Fengtian road station to “Climbing method of door type conversion”.Analys the react of the conversion during the construction,include the displacement and stress variation characteristics of the wall rock and support stress after the excavation.It is point out that the joint of construction passage and station tunnel is the weak links of supporting structure,where principal tensile stress exceed tension-compression strength of concrete.Fnally,contrast the advantages and disadvantages of “Climbing method of door type conversion” and “Expansion excavation method of fan type conversion”.In addition,“Expansion excavation of Benching tunneling method” is put forward according to the “Expansion excavation method of fan type conversion”.The analysis shows that the conversion use “Expansion excavation of Benching tunneling method” is better than “Expansion excavation method of fan type conversion”.