Vol17 No.11: 2840-2852
【Title】Effects of freezing-thawing onthe engineering performance ofcore wall soil materials of a dam in the process of construction
【Author】REN Xiu-ling1,2; YU Qi-hao1*; ZHANG Gui-ke3; YUE Pan3; LIU En-long1,4; ZHANG Zhen-yu1,2; YOU Yan-hui1
【Addresses】1 State Key Laboratory of Frozen Soil Engineering, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China; 2 University of Chinese Academy of Sciences, Beijing 100049, China; 3 Yalong River Hydropower Development Company, Ltd, Chengdu 610065, China; 4 State Key Laboratory of Hydraulics and Mountain River Engineering, College of Water Resources and Hydropower, Sichuan University, Chengdu 610065, China
【Corresponding author】YU Qi-hao
【Citation】Ren XL, Yu QH, Zhang GK, et al. (2020) Effects of freezing-thawing on the engineering performance of core wall soil materials of a dam in the process of construction. Journal of Mountain Science 17(11). https://doi.org/10.1007s11629-020-6264-3
【Abstract】The construction of water conservancy projects in cold regions experiences freezing-thawing cycles, which can greatly change the engineering properties of soil and have a significant impact on the construction of projects. Lianghekou Hydropower Station (LHS), is a controlling station with the largest installed capacity among the 7 middle reach projects in the Yalong River, the secondary tributary of the Yangtze River. LHS is located in a seasonally frozen soil area. Based on the measured data of air and ground temperature in winter in the dam core wall, the freezing-thawing variation of gravelly soil and contact clay during the filling process of the core wall are compared and analyzed, then the main impact factors of the freezing-thawing variation of soils are discussed. The results show that under the influence of air temperature, soil freezes unidirectionally from ground surface downward and deepens gradually, and the thawing processes are different at the aspects of thawing direction and rate. Air temperature and physical properties of soil including soil type, moisture content and dry density affect the freezing-thawing processes of soils.And the impact of engineering construction is more remarkable than natural factors. The engineering construction affects soil temperature and freezing-thawing process by controlling the initial temperature of soil, the speed andduration of the technological conversion of paving, compaction, and the length of placedduration at night.Due to the long placed duration of soil with the slow construction method, the initial temperature of soil gradually reduces, the heat transfer process inside soil is fast. Then the internal heat of soil releases, the decreasing rate of ground temperature of soil at different depths is fast and the frozen depth deepens. While due to the short placed duration of soil with the rapid construction process, the initial temperature of soil is high, high internal heat of soil is supplied every day, and the heat transfer process inside soil is slow. Then the decreasing rate of temperature of soil at different depths is slow, and the variation amplitude of frozen depth is small. This study provides useful guidance for the freezing-thawing prevention during the construction process of core wall dams located at high altitude region in winter.
【Keywords】Lianghekou Hydropower Station (LHS); Gravelly soil; Contact clay; Freezing-thawing variation; Impact factors