ABSTRACT
Mumbai Metro Rail Corporation Ltd is implementing a 33.5 Km fully underground metro rail project, Colaba-Bandra-SEEPZ (Line 3) having 26 UG stations and one At-Grade. The project is substantially completed, and trials and testing are going on in the first reach. Tunnelling work was completed using 17 Tunnel Boring Machines (TBMs) with multiple drives through an array of launching and retrieval shafts. While there were Drive-Through and Drag-Through at some stations, many times the TBMs had to be retrieved, transported and lowered between retrieval and launch shafts for successive drives. Retrieval, transportation, and re-deployment pose significant logistical challenges. Traditionally, TBMs are dismantled into components for transportation and lowering, which is time consuming and messy. The advent of the Strand Jack Gantry System offers a novel approach, potentially trans-forming TBM handling efficiency by enabling the transport and lowering of an intact TBM. Both these methods of retrieval, transportation and lowering were adopted by Package 3 contractor to relaunch the TBMs. This paper aims to compare the effectiveness, cost, time efficiency, and safety of using the Strand Jack Gantry System versus conventional dismantling methods for TBM retrieval, transportation, and lowering and seeks to provide a comprehensive analysis to the decision-makers in tunnel construction projects.
