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                         Experimental study on permeability characteristicsof clay-gravel mixtures
                              under freezing-thawing actions in core wall of earth-rock dams


                                                                                1
                                       LU Yang 1,2 ,LIU Sihong  1,2 ,ZHANG Yonggan ,
                                                    1                1,2        3
                                         YANG Meng ,WANG Liujiang      ,LI Zhuo
                              (1. College of Water Conservancy and Hydropower,Hohai Univ.,Nanjing  210098,China;
                      2. International Joint Laboratory of Long-term Behaviour & Environmentally Friendly Rehabilitation Technologies on Dams,
                                      Nanjing  210098,China;3. Dame Safety Management Department,
                                       Nanjing Hydraulic Research Institute,Nanjing  210029,China))


                   Abstract:Clay-gravel mixture is generally used as the compacted impermeable material in the core wall of
                   high earth-rock dams. In high cold regions, it will endure severe freeze-thaw actions during the construc⁃
                   tion process. In this study,a series of triaxial permeability tests were performed to investigate the evolution
                   law of permeability characteristics after freeze-thaw cycles. The results show that:(1) the permeability coef⁃
                   ficient increased significantly after freeze-thaw cycles,and the degree of increase was controlled by various
                   factors such as confining pressure,number of freeze-thaw,gravel content and the initial molding water con⁃
                               st  nd
                   tent;(2) the 1 -2  cycle of freezing-thawing has the most prominent influence on the increase of permea⁃
                   bility;(3) a lower confining stress and a higher molding water content will dominate the increase of perme⁃
                   ability induced by freeze-thaw actions;(4) the effect of gravel content on the permeability is closely relat⁃
                   ed to the inner meso-structural distribution of clay-gravel particles;(5) the freeze-thaw triggered variation
                   of permeability will significantly increase with increasing the initial molding water contents, and a greater
                   increasing amplitude will be found on the dry side of optimum water content,while a smaller amplitude on
                   the wet side. The results can provide useful guidance for the design of impervious structures in high
                   earth-rock dam as well as the prevention of freeze-thaw damages during its construction in winter.
                   Keywords: high cold region; core-wall dam; clay-gravel mixture; freeze-thaw cycles; permeability; me⁃
                   so-structure
                                                                                   (责任编辑:王冰伟)


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