Engineering Problems And Countermeasures Of Land Reclamation In Tianjin Nangang Industrial Zone

The government of Tianjin Binhai New Area put forward the development strategy of “one city & two ports” in 2009, and the two ports refers to the North Tianjin Port(Beigang District)and the South Tianjin Port(Nangang District). Tianjin Nangang industrial zone targeted at the world-class base of heavy chemical industry and comprehensive functional port. It is planning total area of 200 square kilometers, which contains 162 square kilometers' land area, and 75% of land area comes from coastal reclamation. Unprecedented development opportunities and limited land resources become the main contradiction to limit the development and construction of the Nangang Industrial Zone. Since the start of the construction of Nangang Industrial Zone, many ways have been tried to create land, for example, foundation treatment after backfilling, dredging and coastal reclamation project, inspiring flushes processing and so on.The ground surface of Tianjin Nangang industrial zone is typical marine sediment layer of The Quaternary Period. And part of the original land is low-lying and does not meet the ground elevation of the design. So it needs a thick layer of backfill. The sediment which comes from dredging the harbor and waterway is usually used in hydraulic reclaiming. But the moisture content of the flow mud in the mud disposal area is usually above 100%. That means the underpart of the foundation is still the weak ground which contains under consolidated marine deposit high compressible soil. So reinforcement treatment must be applied to make it qualified construction land. While the heavy chemical industry is the pillar industry of Nangang industrial zone, and so many heavy machinery equipment and aboveground & underground pipeline engineering put forwards high requirements for the bearing capacity and land subsidence control.Although large-scale coastal reclamation can form the land resources for the development of Nangang industrial zone, many problems should be solved firstly in coastal reclamation engineering. For example, the strength and deformation problem of the newly reclamation land, the safety and stability of the marine cofferdam on the weak foundation, and how to optimize the scheme of coastal reclamation to make the new land cater to the use requirements of the design at the lowest cost. This paper has summarized the development course of Nangang industrial zone and the president situation of the engineering, combing the comparative analysis of some other cases of coastal reclamation. The main contents are as follows:(1) Both the development history of the coastal reclamation in domestic and foreign, and the problems of coastal reclamation applied in Tianjin Nangang Industrial Zone have been briefly introduced.(2)To introduce the construction technology and effect of the foundation treatment by vacuum preloading for backfill clay and inspiring flushes processing. Those two reclamation methods and coastal reclamation by vacuum preloading method for dredging clay have been compared in the economic cost respect so as to make the optional choice.(3)The technology and effect of coastal reclamation by using vacuum preloading method to improve dredging clay will be introduced in detail combination with engineering cases, which is widely applied in the construction of Tianjin Nangang Industrial Zone. The cause of the problem that the ground elevation created by this method tends to be relatively low also will be analyzed.(4) This paper proposes increasing the volume of mud by adding the height of the marine cofferdam under the premise of safety and stability of the structure and solving the problem that the ground elevation created by this method tends to be relatively low. And then we use FLAC3 D to check the stability of the heightened marine cofferdam and to propose optional scheme.