Seepage experiences for deep urban excavation at the TBM Malatesta shaft, Rome

Abstract

The realization of a deep excavation in a high hydraulic head condition, in absence of waterproofing treatment at the base, usually needs dewatering systems to control the piezometric condition and, more generically, is employed for lowering the water table within the diaphragm walls. This is a particularly sensitive aspect in the excavation of the new C Line Subway in Rome, where on account of the high density of archaeological remains, the subway stations are at an average depth of 25 meters below ground level. The stations are also characterized by elevated hydraulic loads. The purpose of this paper is to explains the dewatering system used for the TBM Malatesta Shaft, describing the monitoring devices that have been predisposed and the results that have been achieved by the dewatering system during the testing phases. The final section of the paper will cover another dewatering case that will arise in due course along the line, underlining the results and the differences in relation to the first case.