Impact of Deep Excavations on Adjacent Buried Pipelines

Construction of skyscrapers in China encouraged the development of deep excavation designs (e.g., the excavation of Shanghai Jin-mao Tower is 19.5m in depth). Deep excavations usually lie among the dense areas of buildings, roads, and underground pipelines, all of which can be greatly affected by the deep excavations. In severe cases, deep excavations have caused the tilting and cracking of buildings, the settlement of roads, and dramatic deformation and damage of adjacent buried pipelines, thus greatly affected people's daily life. These possible impacts of deep excavations on the adjacent infrastructures remain the key issue in designing deep excavations. The reason is that the strength of earth-retaining structures has been emphasized, while the protection of the surrounding structures was ignored. Deep excavations and the surrounding environment should be considered together as a whole system, and the strength of earth-retaining structures and the protection of adjacent structures should be equally treated in design. In this paper, a 3-D finite element method (FEM) was developed to analyze the interaction among earth-retaining structures, soil, and adjacent buried pipelines. Based on this method, the displacement and the stress of nearby buried pipelines due to excavation were calculated. This paper analyzed the effect of soil improvement on reducing the displacement of buried pipelines. Through analysis of different soil improvement methods, the best protection plan for pipelines was derived. This paper also compared the behavior of buried pipelines with ductile joints with the pipelines with rigid joints. Conclusions drawn in this paper may assist in the design and construction of deep excavations.