Deep excavation clearly impacts existing underlying subway tunnels and threatens their operational safety. The prediction of existing tunnel deformation induced by nearby excavation is a major concern for urban construction. This research presents an analytical calculation method for predicting tunnel deformation induced by upside excavation and also discusses the role of dewatering in the deformation mechanism. First, the existing tunnel is assumed to be nonexistent in the soil, and the vertical unloading stress at the location of the existing tunnel caused by the upper excavation and associated dewatering is calculated. Second, the existing underlying tunnel is simplified as an elastic beam on a Pasternak foundation to calculate its vertical deformation. The proposed method was verified by the good agreement found between the predictions and the field measurements of the construction in the Shenzhen Chegongmiao hub project. Such an analytical method can provide fast and accurate evaluation resul...

An analytical solution is presented to predict ground movement induced by a nonuniformly deforming circular tunnel in a heavy elastic half-plane. Simple expression is proposed to describe the nonuniform soil deformation around the tunnel. The tunnel-deforming components (i.e., ground loss, ovalization, vertical translation) can be determined by the solution-inherent mechanism and by fitting from measured field data. The effects of tunnel-deforming components on the resulting displacement field are discussed. Case studies from various ground conditions were used to check the capacity and applicability of the proposed solution. Although elasticity is a rough representation of the soil behavior, the proposed analytical solution can serve as a simple tool for predicting a reasonable ground settlement profile in the preliminary design of tunnels.

This article presents a low-cost panoramic image stitching system for tunnel lining inspection. The system can produce a high-quality layout panorama of the target lining using photographs taken freely in a tunnel with a hand-held camera and the tunnel design information as inputs. The three-dimensional (3D) freeform shape corresponding to the tunnel design geometry is used as the warping surface for photograph rectification. A newly designed random sample consensus algorithm is used to estimate the freeform tunnel shape from the 3D reconstructed point cloud, which can perform the registration between point sets with different sizes. These processes can make full use of the geometry information of a real tunnel and the reconstructed scene; thus, the photographs can be precisely rectified, and a planar motion stitching can composite them together. Two field applications demonstrate that the system can create a tunnel layout panorama with sufficient accuracy in tunnel lining inspection and that it is applicable to noncircular-shaped tunnels.