Study Of Foundation Construction Technology Under Thin Superstratum And Deep Water Condition

Chengdu is the capital city of Sichuan province and Tianfu new district is the first state-level district in Sichuan.This freight transport channel project is a national investment project.According to the planning,Jinjiang Bridge located on the end of Innovate Road,is going to be built in section K36+860~K37+238 so as to go across the Jinjiang river,which is the main flood passage of city.The channel shape of the crossing position is U type,with a width of 70 m.The 3# pier of the bridge is located within the main river course,the riverbed material being pebble layer with a thick of about 1m-2m.The geological cover is thin,under which there are strong decomposed mudstone with sandstone interlayer,and so the crossing structure is applied.Jinjiang Bridge is 378 m long and its structure forms are as follow: 30 m long simple box girder;cast-in-place continuous box beam with support with a length of35 m,3*60m and 35 m,respectively.The bottom elevation of 3# pile-cap is 441.503 m,the flood level during construction is 451.0m and the pit excavation depth is 9.497 m.Clay is used to build the construction platform.There will be serious water seepage if we still do the excavation as usual,so in this study we intended to verify the water-stopping effect of high-pressure jet piles of double pipe with a diameter of 0.5m in water-stopping structure,support effect of Larssen IV steel sheet pile in pit supporting structure and the final effect in safety of the pit excavation.The content of the study includes construction technology of underwater platform,water-stopping technology,supporting technology of deep foundation cofferdam,excavation technology of deep foundation pit and island construction technology for flood protection in flood season.According to the result of this study,the effect of high-pressure jet piles of double pipe with a diameter of 0.5m in water-stopping structure and use of Larssen IV steel sheet pile in foundation pit support is good.It has a good water-stopping effect;the technology can effectively guarantee the pit construction safety.What’s more,triple-tube high-pressure jet pile can be done along with the construction of bridge piles,effectively avoiding cross-operation during steel plate pile work and saving the time of construction,which is extremely favorable for flood season construction.Through this research,we can promote innovates and breaks in construction technology of platform with deep water and shallow covering stratum.And then,on the base of this research,construction technology of platform with deep water and shallow covering stratum will be extended to a system.With the rapid development of bridge construction,it has broad application prospects and can make further efforts to boost promote and development of construction industry on this technology.