Application of the novel composite earth retaining structure method to urban excavations: a constructability analysis

The objective of this study is to propose and evaluate a novel composite earth retaining structure method to be applied in urban excavations in terms of construction safety, cost, and duration. The novel composite structure is a multipurpose structure, which may counteract uplift pressure acting on the foundation base, provide lateral support at ground level, and function as king posts during excavation. To evaluate the feasibility and advantages of utilizing the composite earth retaining structure in deep excavations, the case of a commercial building development in Taipei has been studied. In this project, the original excavation design employed top-down construction for the foundation and basement. Two alternative designs employing the composite earth retaining structure method were later proposed to the owner for evaluation and selection. The analyses of the two alternatives include a three-dimensional geotechnical finite element analysis using PLAXIS3D and an analysis of time using PROJECT 2013 as well as a study of cost impacts. The results from the analyses show that the novel method can be superior to the original design in terms of construction safety, project cost, and construction duration.