Abstract
Land subsidence threatens the stable operation of urban rail transit, including subways. Obtaining deformation information during the entire life-cycle of a subway becomes a necessary means to guarantee urban safety. Restricted by sensor life and cost, the single-sensor Multi-temporal Interferometric Synthetic Aperture Radar (MTI) technology has been unable to meet the needs of long-term sequence, high-resolution deformation monitoring, especially of linear objects. The multi-sensor MTI time-series fusion (MMTI-TSF) techniques has been proposed to solve this problem, but rarely mentioned. In this paper, an improved MMTI-TSF is systematically explained and its limitations are discussed. Taking the Beijing Subway Network (BSN) as a case study, through cross-validation and timing verification, we find that the improved MMTI-TSF results have higher accuracy (R2 of 98% and, Root Mean Squared Error (RMSE) of 4mm), and compared with 38 leveling points, the fitting effect of the time series is good. We analyzed the characteristics of deformation along the BSN over a 15-year periods. The results suggest that there is a higher risk of instability in the eastern section of Beijing Subway Line 6 (L6). The land subsidence characteristics along the subway lines are related to its position from the subsidence center, and the edge of the subsidence center presents a segmented feature.
Highlights
As the economic and transportation lifeline of big cities, subways play an important role in alleviating the pressure on urban traffic, improving the appearance of a city, and building intensive, green, and smart cities
We focused on the life-cycle deformation characteristics of Beijing Subway Line 6 with severe uneven subsidence (Section 4.3)
The main subsidence areas are located in the two regions of LGY and DBL, which agrees with previous research results [25,33]
Summary
As the economic and transportation lifeline of big cities, subways play an important role in alleviating the pressure on urban traffic, improving the appearance of a city, and building intensive, green, and smart cities. With the increase of uncertain factors, such as long-term natural aging (e.g., material erosion) and transient man-made geological disasters (e.g., land subsidence), as well as the development and utilization of underground space (e.g., construction of underground parking lots or malls, mining of underground water, laying of underground pipeline networks, and encryption of subway networks), the stability and efficiency of the subway will decrease [5] This poses more challenges in accurately assessing the performance of the subway’s entire life cycle. Soil structure deformation caused by uneven ground subsidence will affect the subway track stability [8] The latter involves the future stable operation of the underground project (i.e., the life and performance of the project), which is related to the safety and sustainable development of the city. Monitoring land subsidence of the longer-term subway line is crucial to accurately assess and predict the stability of the subway during its entire life cycle
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