Research On Application Of Two Different Lengths Of Pvds In Vacuum Preloading Method

The soft clay layer is widely distributed in our country's coastline and estuaries delta plain, sharing such features as the high water content, poor permeability, big compressibility and low strength. In recent years, with the economic and social development, project construction land increasingly tense, more and more buildings will be built on this soft ground, which promoting the theoretical research and development of the engineering practice for the soft soil treatment. Vacuum preloading is a relatively mature soft soil treatment method and achieves good economic and social benefits. Tianjin Port, located in Tianjin Binhai New Area, is a man-made port heaped up by silt. Tianjin Port land is a typical soft clay ground, brings adverse effects to the engineering design and construction in the port. Now the country has clearly brought the development and opening of Tianjin Binhai New Area into the overall development strategy. As an important part of the Tianjin Binhai New Area, Tianjin Port gets a rare historical opportunity for rapid development. How to optimize the existing Soft Soil reinforcement method, shorten construct time, reduce project costs for port construction has become a hot topic in research field recently. In this paper, on the review of the vacuum preloading method's historical development and analysis its the current situation, combination of the key projects"Tianjin Dongjiang free trade port zone second battle of 2 million square meters of soft clay foundation treatment"in Tianjin City, carrying out the research work about the length of PVDs in vacuum preloading soft clay treatment to give guidance suggestions for future optimal design and construction. The main contents are as following:(1) Give a brief description of the geology condition in Tianjin Binhai area and applicable foundation treatment method, reviewed the history and current progress of vacuum preloading method in a large area over soft soil reinforced.(2) Describes the basic construction technology of vacuum preloading, and basic elements of on-site monitoring. In practical engineering, installing two different PVDs depths, contrast settlement, pore water pressure dissipation, etc. under the two different circumstances. Before and after foundation reinforcement, by means of the indoor and field tests result, comparing the changes in their physical and mechanical properties to determine the best depth of PVDs.(3) Describes the basic method of calculating settlement, proposed using settlement curve to calculate the final settlement has more practical significance. And used three points, hyperbolic method and the index respectively to calculate the final settlement, thinking the hyperbolic method is more suitable.(4) Emphasized the importance of soil settlements control, discussed rationality of unload standard for the vacuum preloading method in terms of the settlement after construction and give suggestions.