In order to reduce the volume of reclaimed soft ground formed by dumping of dredged soil, the vacuum consolidation method with prefabricated vertical drains (PVD) is one of the most effective methods, which has been frequently applied in Japan. However, it was reported in this method that the PVD installed in the soft ground was bended along with the consolidation settlement. Moreover, the drainage performance of PVD might be decreased due to such bending effect. A series of laboratory tests were performed to evaluate the bending effect on the consolidation behavior in PVD. First, the large scale model tests were performed to measure the shape of PVD bended by the vacuum consolidation. In these tests, the clay slurry at a water content of 150% was consolidated under the vacuum pressure of 60 kPa in the consolidation cells, which were 5 m in height and 30 cm or 76 cm in diameter. It was confirmed in these tests that the bending shape of PVD was explained by the buckling model of a column on an elastic foundation. Second, the permeability test for bended PVD was carried out to evaluate the drainage performance of bended PVD. In this test, PVD were used as sample and the flow rate under a given water head difference was measured. Consequently, it was revealed that the drainage performance of PVD was depended on the curvature and the number of bending points of PVD. Finally, the bending effect of PVD on its consolidation rate was discussed based on all the test results performed in this paper.
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