Research On Ground Foundation Pit Of Qingdao Subway Station On The Soil And Rock Composite Formation

Though the geological conditions are good in most part of Qingdao,but it is complex in deep foundation pit engineering. In the deepfoundation pit engineering, some soil can be excavated directly and thensometimes the rock need to be blasted. What’s more the groundwater alsoeffects the excavation of the deep foundation pit. The geologicalconditions of the pit from up to down is miscellaneous fill, weatheredrock, moderately weathered rock, weak weathered rock and so on. Mostof foundations are located on rock. Most of pit engineering is engineeringthat combined rock and soil. The characteristic of this kind of engineeringis that the upper layers of the pit are soil along with groundwater and thelower layers are rocks.A new kind of supporting structure that developed in this kind ofgeological conditions is that the upper part of the structure are reinforcedconcrete piles and the lower part are advanced-supporting mini steel pipepiles. This kind of structure solved the problem that impact dill worksvery hard on the hard rock layers and its construction process is simpleand saving. Besides, the structure can control the deformation of the piteffectively and ensure the stability of the pit and ensure the safety andnormal use of surrounding buildings.This essay takes advantage of open excavated station pits supporting engineering of Qingdao metro line3and analysis this new kind ofadvanced-supporting mini-steel-pipe piles in basis of FLAC numericalsimulation. The mean work and achievement are the following:（1） This essay analysis some types of pit supporting engineeringof Qingdao open excavated metro stations and introduces their scopes andcharacters, puts forward this new type of supporting structure.（2）This essay introduces our group’s research result of a contrastbetween advanced supporting mini steel pipe piles’ engineeringapplication and laboratory test. Besides, we analysis the change ofmoment after these mini steel pipe piles are forced and theirdeformation and stress mechanism.（3）FLAC can provide these pits’ deformation information andconsider the change in the process of excavation completely. This playsan important part in directing design and construct of these engineering.This essay bases on the calculation principle and characters of FLAC andchooses rational calculation model, unit of the supporting structure andboundary conditions to analysis the stress state of the rock and soil whichwill be excavated. It also introduces the process of numerical simulationon initial stress field and these pits’ excavation and supporting.（4）In the pit supporting engineering of Qingdao Shuangshanstation, we make use of FLAC to analysis and calculate the deformation,and proved the rationality and superiority of this new supporting structure used in Qingdao.The research result of this essay provides powerful support for morewidely use of this new supporting structure.