Abstract: In order to study the influence of deep excavation on the stability of underground utility pipelines that penetrating the supporting wall with different intersection angles, a three-dimensional numerical model of the structure-soil-underground pipeline interaction was established by using FLAC3D commercial software that considering different intersection angles and various excavation depths. The vertical displacement, vertical stress, and axial force in pipelines, which have an important impact on the pipeline stability, are investigated. The results show that when the excavation is in stages 13, the vertical displacement curves of the pipelines at different intersection angles are symmetrically distributed, while in the stages 4-6, the vertical displacement of the pipelines is asymmetric, and the smaller the intersection angle is, the more obvious the non-uniformity of the vertical displacement curve. With increase of the excavation depth, an apparent dipping of the pipeline inside the excavated area was observed. When the included angle is 90°, the vertical stress curve of the pipeline within the range of the excavated area is close to horizontal, and the axial force distribution of the pipeline is “mountain peak”. Whether the axial force curve obtained by considering the orthogonality between the pipeline and the excavated area has a large value of difference. When the included angle is 60°, 74.74° and 80°, a large stress concentration occurs near the supported wall, and a stress concentration also occurs in the middle of the pipeline inside the excavated area. The axial force distribution of the entire pipeline is a sharp “valley” shape. The largest positive axial force appeared near the pit wall, and the largest negative axial force appeared near the middle of the excavated area.

Key words: Deep Excavation, Underground Utility Pipes, Numerical Simulation, Stability