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吕清硕, 张志红, 戴福初.双梯度驱动的非饱和冻土水热耦合模型水资源与水工程学报[J].,2023,34(2):202-207
双梯度驱动的非饱和冻土水热耦合模型
Hydro-thermo coupled model driven by double gradients for unsaturated frozen soil
  
DOI:10.11705/j.issn.1672-643X.2023.02.26
中文关键词:  冻土  水热耦合模型  冻融效应  温度梯度  未冻水含量梯度
英文关键词:frozen soil  hydro-thermo coupled model  freeze-thaw effect  temperature gradient  unfrozen water content gradient
基金项目:科技部“第二次青藏高原综合科学考察研究”专项项目(2019QZKK0905)
作者单位
吕清硕, 张志红, 戴福初 (北京工业大学 城市与工程安全减灾教育部重点实验室北京 100124) 
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中文摘要:
      青藏高原冻土地区的地质灾害与冻土因冻融作用引起的水分重分布密切相关,其实质是复杂水热耦合作用的结果。已有的冻土水热耦合模型较多关注未冻水含量梯度驱动引起的水分迁移过程,而缺乏对温度梯度驱动效应的探讨。基于经典热传导方程和非饱和土体渗流理论,考虑未冻水含量梯度和温度梯度的共同作用,建立了双梯度联合驱动作用下的非饱和冻土水热耦合模型。在采用已有试验数据对模型有效性进行验证的基础上,分别对-5、-10和-15 ℃ 3种环境气温条件下土体的水热响应开展了数值模拟。结果表明:温度梯度在冻结过程中对于水分迁移的驱动作用不可忽略;冻结过程中由于冰水相变释放潜热造成冻结速率逐渐减慢;土中水分聚集的位置处于冻结初期形成的冻结锋面处,且外界气温越低,内外温差越大,则土体水分发生聚集的位置越深,水分迁移量相对也越大,冻结过程中土体水分随深度呈S型分布;-5、-10和-15 ℃环境温度下含水率极值分别位于0.30、0.55和0.70 m深度处,含水率增量分别为3.5%、4.6%和5.5%。
英文摘要:
      The geological disasters in the permafrost regions of Tibet Plateau are closely related to the water redistribution caused by the freezing and thawing of frozen soils, which is the result of complex hydro-thermo coupled process intrinsically. The current hydro-thermo coupled models of frozen soil are mainly designed to describe the water migration process driven by the gradient of unfrozen moisture content, yet the effect of temperature gradient on the coupling process is rarely considered. Based on the classical heat transfer equation and seepage theory of unsaturated soil, a hydro-thermo coupled model driven by double gradients for unsaturated frozen soil was established, in which the combined influence of unfrozen water content gradient and temperature gradient was considered. Then, the proposed model was verified by experimental results, after which a series of numerical simulations were carried out on the hydro-thermo response of the soil under three environmental temperatures, -5, -10 and -15 ℃. The results show that the driving effect of temperature gradient on water migration in the freezing process cannot be ignored. During the freezing process, the freezing rate gradually slows down due to the latent heat released by the phase change of ice-water. The location of water accumulation is at the frozen front formed at the beginning of freezing process. Furthermore, the lower the outside temperature, the greater the internal and external temperature difference, the deeper the location where water accumulates, and the greater the amount of water migration. In addition, the moisture content presents an S-shaped distribution with the depth during the freezing process. Specifically, extreme values of moisture content at -5, -10 and -15℃ are at the depth of 0.30, 0.55 and 0.70 m, and the corresponding increment of moisture content is 3.5%, 4.6% and 5.5%, respectively.
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