| The land of Tianjin Harbor Industrial Zone is formed by the land reclamation in the sea, the foundation soil is come from of the bottom of river and harbor, the water content is very large in the beginning of land formation, the conventional foundation methods of foundation treatment are difficult to obtain a better effect. As the vacuum preloading tests are more and more used in soft foundation treatment, the reinforcement effect of vacuum preloading method obtain more identity. Plastic drainage board has replace the traditional bag sand-well because of the lower cost and convenient construction. Plastic drainage board is the most common vertical drainage system of vacuum preloading tests in recent years. However, according to the data of many years, the pore size of plastic drainage board’s filtration membrane has great effect on soil lost, soil micro-structure and foundation treatment effect. This paper designs the scheme of vacuum preloading, the comparison and selection of plastic drainage board, indoor soil tests and field observation. And make a qualitative analysis on soil microstructure, particle size, pore water pressure dissipation, foundation settlement observation with the help of Tianjin University precision instrument college electron microscopy analysis center and geotechnical laboratory. Emphatically analyzes the difference and relation between the soil microstructure and grain-size distribution curve at the same position of different plastic drainage boards and the different positions of same plastic drainage board. According to the data of macro and micro tests, show that the pore size of plastic drainage board’s filtration membrane is not the smaller, the better. Too small filtration membrane pore size may cause the blockage of drainage channel. Too large filtration membrane pore size may cause the lost of soil. It is very important to control this balance in practical engineering to obtain better effect of foundation reinforcement. |
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