Influence of air temperature change on stability of permafrost slope: A case study of shallow permafrost landslide in Qinghai Province
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摘要:
受气温变化影响，浅层冻土滑坡失稳涉及水分的固液相态转换，是一个复杂的水热力耦合过程。为揭示气温变化对多年冻土斜坡稳定性的影响，基于冻土水热力耦合数值模型，模拟了2020—2024年青海省多年冻土区斜坡水热力演化过程。研究结果表明：水分迁移速率呈周期性变化，每年5—10月活动层融化程度高，总体积含水率变化趋势显著；夏季多年冻土上限以下的高含冰量土层融化产生厚度约15 cm的富水层，孔隙水压难以消散；4年间多年冻土上限下移10.4 cm，导致活动层和富水层的厚度增大，上覆融土下滑力增大、抗滑力减小，土体抗剪强度进一步下降；活动层土体每年产生数厘米冻胀融沉变形，抗剪强度不断劣化，坡脚处最容易形成薄弱带。
Abstract:Under the influence of air temperature change, shallow permafrost landslide is a complex thermal-hydro-mechanical coupling process, which involves the transformation of water between solid state and liquid state. To reveal the influence of air temperature change on the shallow permafrost landslide, based on the coupled thermal-hydro-mechanical model for frozen soil, the thermal-hydro-mechanical evolution process of slope in permafrost region from 2020 to 2024 is simulated. The results are as follows: the rate of water migration presents periodic variation. The thawing degree of the active layer from May to October is high, causing the variation trend of total water content significantly. In summer, the thawing of the high ice content layer below the permafrost table forms a water-rich layer of 15 cm thickness approximately, causing excess pore water pressure difficult to dissipate. The permafrost table will decline by 10.4 cm in 4 years, and the thickness of the active layer and water-rich layer increased. As a result, the sliding force of the overlying thawed soil increases, the sliding resistance decreases, and the shear strength of the soil further decreases. Several centimeters displacement of frost heave and thaw settlement occurs in the active layer per year, shear strength deteriorates continuously, and the weak zone is easiest formed at slope toe.
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表 1 地层物理力学参数
Table 1. Physical and mechanical parameters of formation
参数 活动层 多年冻土层 基岩层 密度/（kg·m−3） 1800 2000 2500 弹性模量/MPa 40 30 5000 泊松比 0.25 0.3 0.15 渗透系数/（m·s−1） 1.2×10−6 8×10−10 0 黏聚力/kPa 12 35 — 内摩擦角/（°） 22 20 — 
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