京津高铁北京段地面沉降监测及结果分析

京津高铁是我国第一条高速运行的城际铁路,其安全运行对轨道变形有着严格的要求.京津高铁北京段经过平原区的沉降区域.地面沉降,尤其是不均匀地面沉降已经引起了部分地段路基和桥梁变形,威胁着高铁的运营安全.因此,需要高精度监测铁路路基和桥梁沉降,分析其原因,进而才能提出缓解沉降灾害的合理措施,保证京津高铁安全运行.本文采用时序干涉测量技术、水准测量技术和分层标监测、地下水分层监测手段相结合,对京津高铁北京段地面沉降进行监测,并利用监测结果分析其差异性沉降成因.结果表明:沿线区域地面沉降发展一定程度上受到来广营凸起、南苑—通县断裂和大兴隆起构造控制;地下水超采是区域地面沉降的主要驱动因素,同时第四系沉积环境、地层岩性和补给条件等共同作用,使得地面沉降发展在空间上存在一定差异性,可以分为微小沉降区(DK0-DK9段)、严重沉降区(DK9-DK27段)和一般沉降区(DK27-DK50);沿线区域地面沉降主要贡献层为中深部地层(50~147.5 m),该层黏性土厚度较大,且主要呈现弹塑性形变,占总沉降量的76%左右,是未来地面沉降调控的主要层位.

Monitoring and analysis of land subsidence along the Beijing-Tianjin high-speed railway (Beijing section)

The Beijing-Tianjin high-speed railway, which passes through a subsidence area in the Beijing plain, is the first high-speed railway of China. Land subsidence, especially differential subsidence, pose a great threat to the bridge stability of this railway. For a safe operation, monitoring of ground subsidence and sediment-compaction around the railway must be conducted. An integrated monitoring program was designed, including time series InSAR, leveling, borehole extensometer and multilayer monitoring of piezometric head, with the aim to delineate the distribution of deformation and to evaluate and identify the main causes for the differential subsidence. The results indicate that the land subsidence pattern is controlled by the Laiguangying uplift, Daxing uplift and Nanyuan-Tongxian fault. Over-exploitation of groundwater, the key factor that drives land subsidence, together with the setting of the Quaternary deposits, variable lithology and recharge conditions can cause the differential subsidence in this region. Regional deformation can be divided into a gentle zone (DK0-DK9), medium zone (DK27-DK50) and severe zone (DK9-DK27). The major clay layer contributing to compaction is located at depth between 50 and 147.5m, which is responsible for around 76% of the total subsidence; exhibiting an elasto-plastic mechanical behavior, which need to reduce groundwater withdrawal.