Construction of An Earth Retaining System in the Heart of CBD- A Case Study

Abstract

The current trend of building skyscrapers in busy urban areas has led to the unique problem of facilitating deep excavation without disturbing the adjacent structures or roads. This excavation support should be both Earth retaining as well as Water Excluding. This paper details the construction of the earth retaining system for the ‘The ONE’ project, located in the heart of CBD (Colombo Business District), and the challenges encountered. Design of the system is also briefly discussed. A secant pile wall consisting of 871 piles was constructed to ensure the water tightness. Inclinometer pipes were installed in the secant pile wall at selected locations to monitor the deflection of the wall during excavation. Additional pressure grouting was carried to ensure stability of the adjacent structures. Boundary scanning was carried out to locate the underground utilities to carry out the temporary ground anchors. In addition to these activities, the paper also briefly discusses the building health monitoring activities carried out during the project.