Deep Excavation for Barra Transportation Junction of Macau: Numerical Analysis of Bedrock Slope Effects on Retaining System

Abstract

The deep excavation and earth retaining system have almost been an inseparable part of a construction project in the area with scarce land resources to seek more underground space, however, reasonably and accurately modelling the excavation and retaining process considering so many factors is the main point of design to ensure the safety of construction and adjacent facilities. The deep excavation for Barra Transportation Junction is a well-documented project, and there is a significant bedrock slope under most areas of the excavation pit. A finite element 2-side model was built to simulate a section with a significant slope with the calibrated model parameters by a finite element 1-side model for where the bedrock slope is not significant. The computed lateral wall displacements show a good consistency with observations, and the 2-side model obtains a behavior that the retaining wall is pushed outward, which can not be simulated by the 1-side model. Then parametric studies were conducted for bedrock under retaining and excavation sides, respectively. It was found that the effects of the bedrock slope on lateral wall displacement were limited, and the bedrock slope under the excavation side mainly impacts lateral wall displacement by the interactions between two sides due to the difference of soil mass through layers of struts. Finally , some recommendations were made for practical deep excavation design based on the previous findings.