青藏铁路冻土区路桥过渡段沉降原因分析

青藏铁路开通近10 a以来,各类冻土工程稳定,保证了列车平稳安全的运行。然而,青藏铁路工程也不可避免出现了一些病害问题。现场调查资料表明,冻土区路桥过渡段下沉现象较为严重。通过冻土区路桥过渡段的沉降特点和工程地质条件综合分析,结果表明:地表水或冻结层上水水热侵蚀,引起人为多年冻土上限下降、高含冰量冻土层融化,致使路基发生强烈的融化下沉。建议这类工程病害应采取主动降温措施增强地基土的冻结能力,并加强防排水设施和改善地表水条件,消除水热侵蚀所产生的融化下沉。研究结果为青藏铁路路桥过渡段的稳定性和养护提供了科学依据。

Settlement analysis of embankment-bridge transition section in the permafrost regions of Qinghai-Tibet Railway

Since the beginning of the Qinghai-Tibet Railway operation,the train has safely run for nearly ten years owing to better stability of permafrost engineering.However,it is also inevitable to appear some damages to the railway.Survey results in-situ show that serious thaw settlement has be found in the transition section between embankment and bridge.Based on the thaw settlement characteristics and analysis of engineering geological conditions,it is found that thermal erosion of subsurface and supra permafrost water lead artificial permafrost table lower and permafrost with high ice content thawing,resulting in extensive thaw settlement of embankment.To transact this damage,measures of keeping cool of permafrost should be taken to strengthen the freeze of roadbed.While,engineering conditions in subsurface water and waterproofing and drainage should be improved to decrease thaw settlement caused by thermal erosion of subsurface and supra permafrost water.This study provides a scientific basis for stabilizing and maintaining the transition section between embankment and bridge.