The Top-down Construction Technique Of Civil Air Defence Underground Structure In Ganzhou City

This paper researches the application of top-down construction technique in a civil air defence underground structure in Ganzhou city. Through meticulous research, this paper presents various technical quality assurance measures, the main work and conclusions are as follows:(A) Engineer should strengthen inspection in excavation process. Standards and survey control points should be laid on the basement and stakes should be evenly laid on joint position of plywood or control lines in the substrate to ensure base excavation smooth and exact location.(B) When pouring concrete, lateral pressure may cause the displacement of reinforcing bars appear. So concrete should be uniform pouring preferably from the middle to the edge. If the steel is displaced, it needs to be timely adjustment.(C) Steel protective layer pads prone to embrittlement. Pad strength not less than the component strength, and can withstand the impact force when placing reinforcement. When the pad supporting the larger bars, it should be added rebar or wire reinforced. When pad is completed, it should be maintained watering.(D)Steel pipe support should be settlement observation, observation once a day, in order to grasp the steel pipe support real-time settlement of the situation. When the detected value of the settlement reached warning value, earthwork excavation should be stopped immediately, and press the emergency plan to take corresponding measures.(E) During construction, excavation of precipitation, excavation width, length, and excavation excavation speed should be key control.(F) Two adjacent walls of the vertical construction joints can not stay in the same line, vertical construction joints must be staggered leaving in order to avoid weakening the structural strength and rigidity.