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青藏铁路多年冻土斜坡段路基稳定性对铁路长期运营具有潜在的威胁,分析评价当前和未来斜坡路基稳定性可指导路基工程的正确设计和施工,从而保证铁路的安全运营。多年冻土地温变化使斜坡路基稳定性分析不同于普通土路基,其冻融交界面位置是制约斜坡路基稳定性的关键所在。通过对安多试验段3 a来的地温监测,分析路基地温变化规律,并预测了未来50 a内试验段地温的变化趋势,建立了当前和未来条件下的斜坡路基稳定性模型,计算分析了斜坡路基的稳定性。通过上述研究,取得以下认识和结论:(1)铁路路堤的填筑,引起多年冻土温度场重分布;由于坡向不对称和几何不对称,使得地温场存在不对称;(2)依据冻融界面位置和活动层的地温特征将冻土路基划分为4个不同时期,即冬季严寒期(1~2月)、春夏融化活动期(3~8月)、最大融深期(9~10月)及回冻活动期(11~12月);通过计算对比分析,每年最大融深期的稳定性系数最小;(3)数值分析的预测结果表明,20 a以后,安多段试验段路基的多年冻土完全退化,在所预测的第10年最大融深期稳定性系数最小。
Subgrade stability of the permafrost slopes on the Qinghai-Tibet Railway is a potential threat to the long-term operation of the railway. The analysis and evaluation of the stability of the current and future slopes can guide the proper design and construction of the subgrade engineering so as to ensure the safe operation of the railway. The change of ground temperature in permafrost makes the stability analysis of slope subgrade different from ordinary soil subgrade. The key point to restrict the stability of slope subgrade is the location of its interface at freezing and thawing. Through the monitoring of ground temperature during the 3-day test period in Anduo, the change law of ground temperature of subgrade is analyzed, and the change trend of ground temperature in the next 50 years is predicted. The stability model of slope subgrade at current and future conditions is established, and the calculation and analysis The stability of slope subgrade. Through the above research, the following findings and conclusions are obtained: (1) The filling of railway embankment causes the redistribution of the temperature field in permafrost; the asymmetry of geostrophic field due to asymmetric slope and geometric asymmetry; (2) The location of the interfacial zone and the geothermal characteristics of the active layer divide the permafrost subgrade into four different periods, that is, the winter frosty season (January to February), the spring to summer thawing period (March to August) and the maximum thawing period (9 ~ October) and the period of re-freezing (11-12 months). By calculation and comparison analysis, the stability coefficient of the maximum thawing period is the smallest each year. (3) The prediction results of numerical analysis show that after 20 years, Permafrost completely degenerated, with the smallest stability factor at the maximum melt-depth of the 10th year predicted.