Laboratory Model Test of EPB Shield Tunneling in a Cobble-Rich Soil

Model tests and field measurements were carried out to study the mechanical behavior of cobble-rich soil in response to shield tunneling. In particular, an experimental investigation was carried out using a laboratory-scale model. The model used includes a miniature shield machine that can approximate real tunnel construction, replicating the in-situ methods of excavation and support. The surface settlement and subsurface deformation were analyzed, and these data were compared with predictions based on previous studies. The results confirm that the model tests can effectively simulate the principal operations of a real earth-pressure-balance machine. The observed surface settlement troughs in both the transverse and longitudinal directions were found to be narrower than in clay or sandy soils. With respect to subsurface deformation, the deformation zone width decreases almost linearly as a function of depth.