Surface Settlement Law Induced by Shield Tunnel Excavation Using Modified Gap Model

GAP model will be modified and programmed by FISH language, which can be used in FLAC2D programs. The modified GAP model is used to study the variation of surface settlement shape with depth, the variation of the maximum settlement value with depth, and the variation of settlement gradient with depth. The results show that: the settlement shape is narrow and deep with the conditions of shallow buried depth of tunnel; on the contrary, the settlement shape is wide and shallow; When the tunnel depth is less than the critical value, the tunnel depth and the maximum surface settlement is approximately linear; when the tunnel depth is greater than the critical value, the curve of maximum surface settlement value with depth becomes flat and with the increase of the tunnel, the surface settlement gradient gradually decreases and eventually tends to zero. It is more reasonable to assess the influence of tunnel excavation near adjacent buildings, using the maximum surface settlement and the settlement gradient as a control standard.