Application of DRASTIC Model for Vulnerability Assessing Land Subsidence of Beijing New Airport Line

Abstract

The article reports a study of the influence of regional land subsidence on the 41km long Beijing New Airport Line. The characteristics of the major compressive geological layers and their potential to settlement are discussed in the light of the past and continuing groundwater exploitation in the area. A DARATIC model for land subsidence quantification was developed and used to predict the differential settlements along the metro line axis. There is a significant difference in the settlement occurring in the north and south areas of the bridge, in part due to the variation in the Quaternary alluvial sediments. The case study highlights the importance of considering both site specific and regional subsidence conditions when designing large structures in such an area. A subsidence parameter is developed to represent the ground deformation gradient, and then used to depict areas where damage risk to urban infrastructure is higher due to fracture propagation. InSAR data was used to evaluate subsidence rates and gradients, integrating hydrogeological and geomechanical variables into a GIS environment. Results show that classic DRASTIC approaches may estimate land subsidence vulnerability in settings such as the one at hand. The integrated vulnerability map shows the high risk imposed on the southern part of the metro line due to the high potential of intensive uneven settlement. Hence, it is concluded that the DRASTIC parameter is a welcome contribution to develop reliable vulnerability assessments in the project.