Abstract: Excavation of foundation pits can cause adverse effects on adjacent pipelines due to the displacement of the surrounding soil. An analytical method for predicting the additional horizontal deformation of adjacent pipelines caused by excavation is proposed using a three-dimensional image source method. Nearby pipelines are treated as Euler-Bernoulli beams on a Pasternak foundation in consideration of the spatial effect of excavation and the spatial distribution of pipelines. The validity of the proposed method is demonstrated through existing cases. Results indicate that the total horizontal deformation of pipelines is primarily induced by the deformation of retaining walls that are adjacent and parallel to the pipelines. The deformation of retaining walls on both sides also significantly impacts the horizontal deformation of pipelines outside the excavation area. The adverse effects of excavation on pipeline's horizontal deformation can be predicted through defining a safety factor and considering different spatial distributions of pipeline. The influence zone of excavation on pipeline deformation can be obtained through plotting contours of the safety factor. When the distance between the pipeline and the retaining wall is within 0.75H (where H is the depth of foundation pit excavation), the safety factor first decreases and then increases with the increase of pipeline's burial depth. The safety factor reaches its minimum when the pipeline is buried at a depth of approximately 1.0H. When the distance between the pipeline and the retaining wall exceeds 0.75H, the safety factor increases with the increase of pipeline's burial depth.

Key words: excavation, spatial effect, adjacent pipeline, virtual image method, contours of safety factor