High Water Ingress during TBM Tunnelling under Andheri Kurla Road, Marol Naka, Mumbai, India.

Abstract

For surface space limitations in metro cities, tunnel is the best option worldwide for the development of modern transport system, utilities and other infrastructures. But tunnelling is full of surprises depending on geological and hydrological factors. Underground Mumbai Metro line -03 is also full of surprises. In this paper we are going to discuss the encountered high water pressure during the Up line mining underneath the Andheri – Kurla road & elevated Mumbai Metro line -01 at Marol Naka. Pressure of water was observed to be 4.5 bars to 5 bars, geotechnical instruments showing no settlement but tunnel always filled with muck and progress were affected badly apart from taking precautions during the mining. As per geology, grade III basal and breccia were encountered. Team tried to find out the source/causes of this high water ingress but even after searching various options such as utility damage, recharging with water body, geological & geophysical investigation options, it was unable to conclude the confirm source. It was very astounding that no high water ingress was observed during the down line TBM mining. In this paper, all options have been discussed in details and also suggesting for taking high precautions during construction of cross passage in this area.