Deformation Monitoring and Law of Beijing Metro Line 6 (Phase II)

Subway underground construction generally carried out at urban downtown areas. It has various buildings and facilities, and complicated underground pipe network condition. Underground projects such as the construction of new metro line and deep foundation pit excavation will cause damage to the geological environment which has balance stress. And it also easily lead to deformation in the project construction area, and even surface collapse. Therefore, it is of great significance for the regular deformation monitoring of the surrounding environment during the construction of the metro line.Taking Beijing Metro Line 6 (Phase II) as the research object, 33 scenes TerraSAR-X data in 2011 -2015 were collected, and IPTA technology was used to obtain the deformation results in the study area. The spatial statistics method was used to analyze the results of InSAR, and the reliability of the results was evaluated. And with the leveling results as a standard, the accuracy of the deformation results was evaluated. Based on the achievement of InSAR, combined with geological structure, hydrogeology, engineering geology, groundwater information and engineering construction progress, etc, the rule of settlement development along Beijing Metro Line 6 (Phase II) was studied to explore the impact of railway engineering on the surrounding environment.The research show that the deformation results obtain by IPTA technology can achieve high precision. Compared with leveling results, the absolute deviation is less than 10mm/year and the standard deviation is within 6mm/year. Beijing Metro Line 6 (Phase II) project passes through the key subsidence area of Beijing. The Section analysis method was used to extract the deformation profile, so as to express the degree of uneven settlement by the gradient of the profile. As a result, the fluctuation of uneven degree was presented along the surface line, and some sections have higher values.Overlaying the engineering geological profile of subway lines and the location information of subway stations, it was found that the excavation of subway station has a great impact on the surrounding environment, and the influence is more obvious with the increase of clay layer thickness. The groundwater level along the Line 6 (Phase 2) gradually increased from Caofang Station to Dongxiaoying Station. Overall, the sedimentation rate of low groundwater level is higher.The deformation monitoring of underground rail transit surrounding environment based on multi-discipline crossing is conducive to guiding engineering construction and engineering operation protection. It is significanct to the safety of railways. This research can also provide reference for other subway construction and monitoring.