Design, Construction and Uncertainties of a Deep Excavation Adjacent to the High-Rise Building

In present infrastructure development, deeper basements are provided to satisfy parking scarcity. Safety and economy decide the system of shoring to go deeper below the ground level. This paper provides the design and construction of a deep excavation for an office building located at Bengaluru. Finite element model developed through PLAXIS 2D software is used for designing the shoring system in the present case study. The design and construction of two different deep excavation schemes are discussed in this paper, they are proposed based on the soil profile, constraint of space, presence of adjacent structures and service lines. Along the excavation line at some locations, existing buildings were located in very close proximity leading to lack of space for providing required slope for stabilising with driven nails, so in order to keep the excavation sides stable in those locations contiguous pile with soil/rock anchors was proposed. This deep excavation was of particular interest because of the uncertainties faced during construction which lead to failure of almost 20 m deep slope adjacent to existing high-rise building. The existing adjacent high-rise building was fully functional at the time of deep excavation. Potential large deformation of the adjacent high-rise building caused due to slope failure was one of the main concerns immediately after the failure. The immediate remedial measures taken to safeguard the footing of the existing high-rise building has also been included in this paper. The measure includes like immediate backfilling followed by grouted nail proposed along the failure surface.