A case study on performances of overlying pipelines due to shallow tunnels excavation in water-rich gravel ground

Abstract

Twin rectangular-shaped tunnels were constructed vertically beneath the adjacent pipelines in water-rich gravel ground. An analysis was carried out using measured datum to reveal the response of the overlying pipelines to the construction of shallow tunnels. The method of superposition was applied for describing the displacement profile of the overlying pipelines. The transverse profile shapes for the pipelines remain different. The profile of the gas pipeline and box culvert firstly displays a single-trough “n” shape and “U” shape, respectively, whereas the final profile of the pipelines displays an unsymmetrical double-trough “W” shape. It is also found that the safety of the existing pipelines was generally ensured, except for one monitoring point of the box culvert on the right side of the shallow tunnel. It implies that the larger grouting thickness beyond the excavated outline of the shallow tunnel should be conducted in similar cases.