Innovative Top-Down Construction Method with a Sequential Peripheral Wall

This paper presents an innovative top-down construction method using a sequential peripheral wall (SPW) approach. The top-down method is a safe approach to deep excavation in an urban area. The conventional top-down approach begins with construction of an integrated peripheral wall before excavation to the final depth. The wall then is stabilized as the main structure is gradually built. In the SPW top-down approach, the peripheral wall is built gradually and sequentially from top to bottom. This changes the geotechnical behavior of the structure in performance and execution. The present article introduces and explains the SPW top-down approach and presents a case study of a project in Tehran. The behavior of the structure is studied from the geotechnical and structural perspectives by three-dimensional numerical modeling. The SPW top-down approach can be used for favorable geotechnical conditions in which considerable arching stress is mobilized during excavation. Geotechnical prerequisites are required for the use of the SPW approach, such as data on the groundwater table and stand-up time of the soil. Also, during the construction phase, it is recommended to combine the observational method with comprehensive construction monitoring. In many cases, the SPW approach can reduce material consumption as well as the time and cost of the projects, which can lead to a sustainable project.