Three-Dimensional Numerical Analysis on the Influence of Buttress Wall Removal Timing on the Lateral Deformation of Diaphragm Walls during Deep Excavation

Urban areas in Taiwan are densely populated with limited land. Excavation often takes place near existing buildings, necessitating protective measures for adjacent properties. Among these measures, cross walls or buttress walls are commonly employed, especially in weak foundation soils, which have seen many successful applications. These mechanisms mainly contribute to reducing lateral deformation of the diaphragm walls, ground subsidence, and excavation face uplift. However, the behavior of these walls is essentially three-dimensional, and common engineering analyses employing one-dimensional elastoplastic beam analysis cannot adequately simulate their mechanical behavior. This study utilized the PLAXIS 3D 2018 software to analyze real-life cases of buttress walls and cross walls. Then, the results of the numerical models were validated against actual field measurements, and the outcomes were satisfactory, and within the regulatory allowable values. The primary objective of this study was to find the influence of different buttress wall removal timings on the lateral deformation of the diaphragm wall. The findings suggest that the gradual removal of buttress walls will effectively control the lateral deformation of diaphragm walls during the excavation of deeper floors like mezzanines.

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