The Construction Technology Research Of Metro Foundation Pit In Granite Weathering Layer

Granite weathering layer as a special stratum in Guangzhou area is widely distributed.Due to its easy to be softened in water and disintegrable properties brought a lot of difficultiesand risks to the Guangzhou Metro foundation pit engineering construction. Obviously thetechnology research on the granite weathereing layer characteristics and local layer retainingstructure design and construction has good practical value and social economic benefits.Through the analysis of the completed the granite weathering layer foundation pitretaining structure design and construction, combining with relevant construction cases andthe problems in Guangzhou Metro construction, there two respects could be proceeded,emphatically from the retaining structure design and construction control of lowering thewater level. Making full use of granite weathered layer easy to be softened in waterdisintegrable properties, optimizing the retaining structure design technology and constructiontechnology, through which maximize technical economic benefit based on the premise oflowering project risks and ensuring project safety. This can not only provide good referencebut be popularized in future in open-cut subway foundation pit engineering.This paper studied mainly with the following aspects of granite weathering layerfoundation pit retaining structure design and construction technology:1. The geological characteristics of Granite weathering layer and the engineeringcharacteristics in Guangzhou area, from the original cause of formation, composition andother aspects of granite weathering layer to analyze the mechenism of beingsoftened-in-water-disintegrable, to explain the adverse effects of the granite weathering layercharacteristics on the engineering;2. Through summarizing the subway station’s foundation pit retaining structure in graniteweathering layers, to explain the application of the reasonable retaining structure.the layer;3. Introducing respectively several major construction technics in granite weatheringopen-cut excavation construction technology and attentions, including: enclosure selection ofstructure embedded depth, advancing grouting for water-proof construction technology,construction technology of precipitation and excavation of foundation pit bottom constructiontechnology;4. through practical engineering example, to explain the applications and development ofgranite weathering layer in subway foundation pit construction technology, and analyze theexisting problems and solutions.