Performance of a Deep Top-Down Excavation under Operating Railway

Abstract

In this paper, the construction and performance of a deep metro station excavation is presented. Top-down construction method has to be used in this deep excavation as it is located under the high speed railway, and the potential deformations of both structures and railway subgrade are extremely large. In order to reduce the deformations and ensure safety during the construction, several design and construction measures were taken including the thickening diaphragm walls, two additional temporary concrete struts, large area of soil improvement, and dense drilled piles. Additionally, a novel excavation method is used to improve construction efficiency. Field performance data were collected (i.e., lateral wall deflections, vertical displacements of diaphragm wall, middle slabs and railway subgrade, and support system loads). Results are comprehensively analyzed and show that the deformations of structures and railway subgrade are controlled within limited range.