Research Of Air Passage Into The Main Body Construction Technology In Jiefang Road Station Of Changchun Subway

Considering that tunnel construction methodsare complicated and different methodshave high demand on the construction environment, hydrogeology and formation lithology,a proper construction method plays the key work on the excavation of the wholeunderground engineering. It is related with not only the whole construction difficulty degreeand schedule, but also the construction safety. Combined with the interchangeengineering ofLiberation Road subway stationin Changchun, the finite element software, FLAC-3D isused for the modeling research on the entering-the-hole processfrom the duct to the stationbody. And the main contents conclude the following aspects.1. The summary analysis on the engineering and geological situation of the LiberationRoad subway station in Changchun.2. The simulation analysis on the research of entering the station from the duct ofMetro Line2Liberation Road subway station in Changchun.3. Three schemes, breaking the horsehead directly, double arch hoist and strengthenedring beam are simulated by FLAC-3D and compared by settlement, the key processstress and the plastic zone and other technical indicators and the optimal solution isdetermined. Comparing the strengthened ring beam with the actual monitoring data,the effectiveness of the numerical simulation is proved, which can provideexperience for the following engineering.The research gets the following results:1. During the process of CRD method duct excavation, double arch hoist has the bettercontrol on the settlement than breaking the horsehead directly and strengthened ringbeam, reflecting in the both the settlement caused by every step and the maximum.The main reason is that, this way need a more duct and the stress that should bestand by one is spread on the double arch, releasing the stress concentration of thevault. Considering the horizontal displacement caused by three schemes are allsmall, we can know these three schemes can all fully mobilize the independentability of surrounding rock and effectively prevent the lateral movement ofsurrounding rock.2. At the top of Metro Line2and the connection of duct and Metro Line2, during thePBA method station body excavation, when initialbranch and the medium plate are made, the settlement of strengthened ring beam is the minimum, then is double archhoist and the one of breaking the horsehead directly is the maximum.3. The maximum stress of double arch hoist during the duct excavation is theminimum. When initialbranch and the medium plate are made and during thestation is excavated, the one of strengthened ring beam is the least and breaking thehorsehead directly is the most. So strengthened ring beam has an obvious effect onthe stress concentration. Meanwhile, double arch hoist can easily form the stressconcentration around thecentral axisof duct and column, so the plastic zone of it isthe maximum and breaking the horsehead directly is the second. While thestrengthened ring beamhas the best control on the plastic zone.The result shows that, in spite of the special geological environment of Changchun,during the entering-the-hole process from the duct to the station body, optimally consideringto strengthen the ring beam first, then break the horsehead should be a relatively safe andreasonable way. It must have certain significance for the Changchun subway construction inthe future.