Land subsidence along the Beijing-Tianjin Intercity Railway during the period of the South-to-North Water Diversion Project

摘要

The Beijing-Tianjin Intercity Railway (BTR) passes through the subsidence centre of the Chaoyang Wangsiying-Heizhuanghu subsidence funnel edge, which is the most serious subsidence areas in the Beijing Plain. In this paper, we performed Persistent Scatterers Interferometry (PSI) time-series analyses technique to investigate land subsidence along the BTR with ENVISAT-ASAR, TerraSAR-X, and Sentinel-1 data. We found the serious subsidence area occupies 14.6% of the total area and reaches a maximum rate of 70 mm yr(-1) in Dougezhuang. Sequential subsidence aggregation obtained by global Moran's I shows that the subsidence heterogeneity is the greatest in 2013. Using the Getis-Ord statistics, the uneven sections of spatial subsidence along the railway are DK7-11 and DK21-23. Combining the compressible layer thickness with groundwater data reveals that the greater the compressible layer thickness, the more serious the subsidence is and the correlation is highest between the extraction of groundwater from the second and third layers and the ground subsidence. With the start of the South-to-North Water Diversion Project, the extraction of groundwater began to slow, but the slowing trend of subsidence was not obvious because of the lag between groundwater and land subsidence.