| Beijing capital international airport west runway is the main runway landing international flights. L taxiway,which connects the west runway and the No.4 parking apron and terminal 2 apron, is one of the busiest airport taxiways,and also must be delivered across the slide.by airport south China air freight to north cargo bay and the terminal between the No.1 and the No.2.Due to the van taxi back to the aircraft are often leads to many flights stopping slipping and waitting. This not only affect the normal flight takeoff and sliding safety, also cause a lot of goods overstocking, bring huge economic losses of airport, and affect the international image. The new project described by this paper is to jack into box culverts as freight channel under the roof of L taxiway, which will thoroughly solve the contradiction.of the freight cars and airplanes avoiding each other.The research objectives of this paper is mostly to solve the issues of anti-landslide on the working face, aircraft taxiway subsidence control, the reduction of resistance ,the downward-sloping and the left or right deviation in the process of box culvert jacking.The research contents of this paper includes five main construction technology and the surface subsidence analysis.The five major construction technologies are:①the construction technology of high-precision and long-big pipe roof;②small guide hole and slideway construction technology;③relay box culvert jacking construction technology ;④chemical slurry lubrication and the reduction of resistance technologies;⑤the joints of box culvert excavation and the jacking-expansion then cast-in-place technology. for curve box. The surface subsidence analysis content includes two-dimensional finite element analysis. for the surface subsidence,which is caused by pipe roof, small pilot holes and jacking box culvert.The research method of this paper is to apply the geomechanics theory and finite element numerical analysis method to study the stress field and displacement field of the culvert box with the surrounding soil , to analyze the construction process, to compare and optimize the construction scheme, and combined with the feedback of actual monitoring and measurement data to explore the optimized construction method and process of the culvert box jacking while the aircraft would not stop flying.The research results are mainly reflected in the following areas:(1)To prevent working face from landslip, the works penetratedφ325mm 148m long pipe roof by precision for one-time, there is no precedent in China.(2)Small guide hole at the bottom of the box culvert and slideway inside the small guide hole construction technology successfully solved the problems of downward-sloping , left or right deviation and aircraft taxiway subsidence .Specification states: two-way jacking, when the culvert length is less than 50m, the butt joint elevation h = 30cm, for the works height difference is less than 20mm, left or right deviation is less than 50mm, the aircraft taxiway settlement value is less than 1/3000, all ranking first in the domestic engineering field.(3)The mud used in the project impacted the efficiency of decreasing resistance up to 60% to 80%, which the groundwater does not break down, do not penetrate to the soil and is not drying hard to ensure that the box culvert is not locked when it is to re-start in a few days to stop driving or the push time for more than 3 months. (4)The box culvert of the project is rectangular box with two holes, length 148m, width 13.9m, height 6.5m, the longest and the largest jacking box culvert in china .(5)The top of the box culvert of the project is 5m deep, plane load is 400t / axial compression, which is the most weight in china.There is not the precedent to build a double-hole freight tunnel under the runway in the condition of non-stop flight at present in china. |
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