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U型块石路基作为块石护坡与块石基底两种结构路基的组合,同时也作为青藏铁路的一种主要补强措施,其在高温冻土区的长期降温效果备受关注。基于长期的现场监测资料,对青藏铁路楚玛尔河高温冻土区一处U型块石路基的长期降温过程、降温机制以及变形特征进行了研究。结果表明:U型块石路基表现出持续稳定的降温效果,路基下部多年冻土上限附近降温明显,上限抬升迅速,且进入稳定状态。基底块石层底、顶板温差存在明显冷暖季差异。阴坡侧块石层每年1月至3月初为相对强烈自然对流期,阳坡侧相对缩短半个月时间。受工程热扰动影响,深层的多年冻土在经历2~3年升温过程后,呈现显著的降温过程。路基变形整体表现为较小的沉降量,变形主要来源于早期路基下部高温冻土层的压缩变形。总之,U型块石路基在高温冻土区表现出长期有效的降温效果,变形量有限且已趋于稳定,路基整体稳定性可以得到保证。
As a combination of block embankment and block foundation, U-shaped block roadbed also serves as a major reinforcement measure for the Qinghai-Tibet Railway, and its long-term cooling effect in high-temperature permafrost areas has attracted much attention. Based on long-term field monitoring data, the long-term cooling process, cooling mechanism and deformation characteristics of a U-shaped block embankment in the high temperature permafrost area of the Qinghai-Tibet Railway were studied. The results show that the U-shaped block embankment shows a continuous and steady cooling effect. The cooling temperature is obviously lower near the upper permafrost lower part of the subgrade, and the upper limit rises rapidly and enters a steady state. Base block stone floor, roof temperature difference between the obvious cold and warm season. The shady side of the rock mass is relatively strong natural convection from January to early March each year, while the side of the slope is relatively shortened by half a month. Affected by the thermal disturbance of the project, the deep permafrost shows a significant cooling process after 2 or 3 years of warming. The deformation of subgrade manifests itself as a smaller settlement, which is mainly due to the compressive deformation of the permafrost layer in the lower part of the subgrade. In short, the U-shaped block roadbed in the permafrost shows long-term effective cooling effect, deformation is limited and has stabilized, the overall stability of subgrade can be guaranteed.