Experimental study on the clogging effect of dredged fill surrounding the PVD under vacuum preloading |
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| Affiliation: | 1. Department of Civil Engineering, Industrial University of Ho Chi Minh City, Ho Chi Minh City 700000, Viet Nam;2. Department of Civil Engineering, Ho Chi Minh City University of Technology, Vietnam National University, HCM City, Ho Chi Minh City 700000, Viet Nam;3. Department of Ocean Engineering, Pukyong National University, Busan 608-737, Republic of Korea;1. Department of Civil Engineering and Architecture, Saga University, Japan;2. College of Architecture and Civil Engineering, Wenzhou University, Wenzhou, Zhejiang 325035, China;3. Department of Civil and Environmental Engineering, College of Engineering, Shantou University, Shantou, Guangdong 515063, China;1. State Key Laboratory of Hydraulic Engineering Simulation and Safety, Tianjin University, 135 Yaguan Road, Jinnan District, Tianjin 300350, China;2. School of Civil Engineering, Tianjin University, 135 Yaguan Road, Jinnan District, Tianjin 300350, China;3. School of Civil Engineering, Hebei University of Engineering, 199 Guangming Street, Hanshan District, Handan City, Hebei Province, 056038, China;4. CCCC Tianjin Port Engineering Institute Co. Ltd, Tianjin 300222, China;5. Tianjin Research Institute of Water Transport Engineering, Ministry of Transport, Tianjin 300456, China |
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| Abstract: | Clogging effect surrounding prefabricated vertical drains (PVDs) is a typical problem when vacuum preloading is applied to a dredged fill foundation. A large-scale model test was designed to clarify the cause and mechanism of the clogging effect, and the basic physical and mechanical parameters of the soil in the clogging zone were tracked during the test. The results demonstrated that a clogging zone was formed around the PVD in the early stage of improvement with conventional vacuum preloading, and the boundary of the clogging zone was approximately 0.2–0.4 of the boundary radius. The clogging zone surrounding the PVD was formed because of the overall movement of the soil toward the PVD under the high vacuum pressure gradient, rather than fine particle migration. The soil in the clogging zone exhibited permeability anisotropy and equivalent ‘smear’ effect. The permeability ratio (kh/kv) was less than 1, and the ratio of horizontal permeability coefficients at the test distances of 45 cm and 10 cm were 9.6 at a depth of 20 cm and 8.9 at a depth of 80 cm. An analysis of the microstructure of the soil in the clogging zone demonstrated that the clay particles tended to be vertically oriented. The re-orientation of the clay particles reduced the horizontal permeability coefficient and led to the permeability anisotropy of the soil in the clogging zone. Thus, decrease in the horizontal permeability coefficient and equivalent ‘smear’ effect of the soil in the clogging zone affect the consolidation of dredged fill, which leads to the clogging effect. The permeability anisotropy also slightly affects consolidation. |
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| Keywords: | Geosynthetics Vacuum preloading Clogging effect PVD Dredged fill Permeability anisotropy Equivalent ‘smear’ effect |
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