OasisLMS

Urban development in this era demands construction activities to be carried out in a cost-effective manner that requires maximum utilization of available land area. The demand for underground structures like metro stations and basement parking are on the rise. The paper discusses about a deep excavation for an office building in a metropolitan city in India. The proposed excavation is for a Six-level basement parking area with an excavation depth of 17m. Deep excavation along with removal of existing irregular geometry of basement  along with piles made the excavation  more complex. The site located in center of the city posed a great challenge for excavation works due to proximity of adjacent high-rise buildings, a major arterial road running close to site and metro tunnel is about 7m from the site boundary. The subsurface profile at site consists of fine sands underlain by soft to very soft clay followed by hard clay and then weathered shale.  The design water table is considered at Ground Level. The analysis is carried out based on the soil parameters considering weakest borehole. The temporary retaining system consisted of a 1000mm thick diaphragm wall with four levels of support using temporary steel struts and waler beams. The analysis for the excavation shoring system was carried out using geotechnical analysis softwares Wallap and Plaxis. The diaphragm wall was designed for a depth of 23m and the total perimeter of the wall was 185m. Uplift anchor piles were installed at the raft level to mitigate the uplift pressure due to water. Instrumentation such as inclinometer, ground settlement marker, strain gauges were installed and monitored.

Sathishkumar E, L&T GeoStructure; Gopinath M., L&T GeoStructure; M. Kumaran, L&T GeoStructure

International Conference Proceedings