青藏铁路多年冻土区长期监测系统的研究与应用

Study and Application of Long-term Monitoring System for Permafrost Area along Qinghai-Tibet Railway

研究目的:青藏高原多年冻土区现存的地质地貌形态是经过漫长的地质历史时期形成的,部分多年冻土区的年平均气温相对较高,冻土厚度较薄,热稳定性较差,冻土的稳定性直接关系到上部工程结构的稳定性和耐久性。研究和掌握多年冻土环境变化对工程结构稳定性影响的途径和方法,可以了解青藏铁路沿线多年冻土区气候变化情况和气候影响下的冻土发展趋势,为青藏铁路制定工程防治措施提供依据。研究结论:(1)通过对近几年的监测数据分析来看,青藏铁路长期监测系统运行良好,监测数据真实可靠,能够作为青藏铁路冻土区工程稳定性评价的依据;(2)利用长期监测系统对多年冻土路基地段进行了多年连续监测,发现了出现较大沉降变形冻土路基的环境特征以及沉降机理、据此拟定出着眼维持路基状态、改善路基系统水热条件、缓解人为上限下降、减缓路基沉降速率的工程补强措施;(3)通过长期监测系统对桥梁、涵洞断面的监测和分析,认为多年冻土区桥涵基础目前整体上是稳定的。

Research purposes： The existing geological condition and land form of the permafrost area along Qinghai-Tibet Railway have gradually formed in a long-term geologic history period with features of relative high average temperature,thin frozen soil and poor heat stability in some parts of the permafrost area.The stability of the frozen soil directly relates to the stability and durability of the superstructure of the railway track.Researching the way for knowing the influence of the environment change of frozen soil on the superstructure of track can make the development trend of the frozen soil understood under the condition of climate change.It can provide the basis for taking the preventive measures for Qinghai-Tibet Railway.Research conclusions：（1） From the monitored data in recent years,it can be seen that the long-term monitoring system for Qinghai-Tibet Railway has worked well.The monitored data are true and reliable.They can be as the basis for evaluation of the stability of engineering structure in permafrost area along Qinghai-Tibet Railway.（2） The long-term monitoring system has continuously monitored the subgrade in permafrost area for many years and found out the environment characteristics and settlement mechanism of the subgrade in permafrost area when the subgrade occurred big settlement and deformation.Based on them,the strengthened measures will be presented to better maintain the subgrade,improve the water thermal condition for the subgrade system,relax the drop of manual upper limit and slow down the settlement rate of the subgrade.（3） From the analysis of the monitored data on the bridge and the cross-section of culvert in permafrost area,it is believed the foundations of the bridges and culverts are entirely stable.