Top-Down Construction Method And It’s Application In The Separate Civil Air Defence Basement

With the development of the urban construction, the area of city land hasdecreased gradually. The modern building has extended to the high altitude and theunderground, therefore the deep foundation pit engineering has become one of themost common solutions. The construction sites are become more narrow, thetraditional construction method from underground to over ground could not meet therequirements of construction. As a result, top-down construction method appears andhas been widely used. The practice of top-down construction method in theengineering project has proved that this method for underground structure can bringcomprehensive benefits to the project.Based on the present situation of top-down construction method in deep buildingfoundation pit, the author illustrated the basic principle，technology，classification，advantage and disadvantage of this method and analyzed same key problems such asdiaphragm wall construction, mid-maintain columniation construction, concrete cast,vertical transportation, the structural member nodes construction, foundation pitdewatering, the settlement and deformation control of the underground structure andenvironment.With the development of the economy, civil air defence works has become moresignificant and the utility of urban underground space and the construction of civil airdefence basement project increase continually. Most of these projects have adoptedtop-down construction method to meet the requirements of construction duration, cost,environmental protection, safety and so on. The skill of top-down constructionmethod used in separate civil air defence basement has the advantages that traditionalconstruction method can not compared——could restore the urban transportationquickly, reduce the negative effects on surrounding environment and building, makethe structural design more rational, gets the more effective economic efficiency andsocial benefits.The thesis discussed the main difference top-down construction method betweenseparate civil air defence basement and deep building foundations pit, the construction of vertical structural member, such as diaphragm wall and mid-maintaincolumniation, will use top-down construction method when the separate civil airdefence basemen use top-down construction method and the construction processwould be more complex than the top-down construction method of commonfoundations pit. This paper based on one of separate civil air defence basementengineering in Putian, which uses top-down construction method in the whole work,studyed some special techniques such as earthwork excavating, formworkconstructing, reinforced constructing, concrete constructing and construction jointsettings in the project and give some possible solutions. When using top-downconstruction method, the monitoring of the whole construction process would beextremely significant and the thesis also analyze the monitoring methods with anengineering example.Finally, the author also put forward several problems about top-downconstruction method for separate civil air defence basement in the paper, whichshould be made greet efforts to solve．...