冻土中的含水量和含冰量受温度直接影响,因此温度对季节性冻土的冻结层的力学性质有显著的影响.北方寒冷地区水渠的地震动力响应随季节变化会呈现出差异.该文运用冻土物理学、冻土力学、数值传热学、高等土力学及土动力学等基本理论,建立了北方寒冷地区水渠的水-热-动力耦合数学模型,并编制了相应的数值分析程序.最后,以北方寒冷地区某一监测输水渠道为例,对修建后第10年水渠在地震荷载作用下的2个典型时期的地震动力响应问题进行了数值分析.结果表明,当发生地震时,水渠加速度呈显著季节差异,渠底和渠顶加速度在温度环境最低时(1月15日)最大值分别为1.160、1.476 m/s2,在温度环境最高时(7月15日)其最大值分别为1.360、1.785 m/s2;水渠速度无显著差异,渠底和渠顶的水平速度在1月15日最大值分别是0.145和0.149 m/s,7月15日其最大值分别是0.146和0.150 m/s;在地震结束后,水渠发生残余位移并呈倾斜分布,渠堤出现较大的相对位移,7月15日水渠最大位移为5.6 cm.该研究成果可为北方寒冷地区同类型工程的设计与维护提供参考.%Because of its direct influence on the amount of unfrozen water and ice lens in a frozen soil, temperature has a significant effect on the mechanical behavior of the freeze-thaw soil. Accordingly, seismic responses of engineering structures such as canals in northern cold regions exhibit noticeable differences with seasonal alternation. To analyze the distinctive seismic characteristics of a canal in northern cold regions, a coupled water-heat-dynamics model was built based on theories of heat transfer, soil moisture dynamics, frozen soil mechanics, and soil dynamics. A well-monitored canal in northern cold regions was used to simulate seismic responses in two typical seasons in the 10th service year. The numerical results showed that the constructed canal disturbed the original thermal state and the geo-temperatures of the canal changed with seasonal alternation. In the freezing-thawing process, the unfrozen water migrated and ice lens formed in the canal soil under the forcing of temperature gradient. As a result, the unfrozen water and ice distributions of the canal exhibited obvious seasonal differences. For instance, there were little unfrozen water and much ice lens in the canal and shallow layer of soil at air temperature bellowing freezing, whereas the volumetric content of the unfrozen water was high and the ice content was equal to 0 when the temperature had its maximum during the year ( July 15). So the differential seismic responses of the canal were generated by different water-heat states in the two seasons. Among these two seasons in the 10th service year, although the general time histories of the acceleration and velocity were similar in the canal, their maximum amplitudes were relatively larger on July 15. For instance, in two different time (January 15, July 15), the accelerations of the canal bottom respectively got their maximum acceleration values which were 1.160, 1.360 m/s2in 12.165 and 2.404 s, whereas the accelerations of the canal top got their respectively in 8.995 s and 9.007 s maximum values which were 1.476, 1.785 m/s2, so the earthquake accelerations of the canal were stronger on July 15 than January 15 under the earthquake. The horizontal velocity responses of the bottom and the top of the canal were smaller on January 15, their maximum velocity was 0.145 and 0.149 m/s, respectively, while the maximum speed was 0.146 m/s and 0.150 m/s, respectively on July 15. The displacement was a direct expression of the seismic loading and also sensitive to temperature variation, the displacement responses of the canal to dynamic loading are also relatively larger on July 15 and the maximum horizontal displacement was 5.6 cm in the example. When the earthquake was over, there were still permanent differential deformations in the canal, and the residual displacement distributions of the canal were asymmetrical. In fact, the seismic response of the canal in seasonally frozen soil area was a very complicated water-heat-dynamic coupled problem, so there were few theoretical documents on the subject up to now. As a preliminary study, the numerical model proposed in this paper has some limitations. Therefore, further studies should be carried out on the subject. As a preliminary exploration, it is expected to provide theoretical basis and reference for design, construction, and maintenance of the canal in seasonally frozen regions.
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