New Delhi Metro Extension Project

Project Overview

Phase II of the New Delhi Metro Extension Project is an ambitious plan to add 53 km (33 mi) of new rail lines to cut transportation times, in particular for when the city hosted the Commonwealth Games in 2010. Owners Delhi Metro Rail Corporation (DMRC) completed Phase I of the project in November 2006, adding 65 km (40 mi) of track and 59 stations. Phase II, at a cost of USD $1.8 billion, involved multiple soft ground tunnels to be bored by Earth Pressure Balance Machines (EPBMs) between underground stations excavated by cut and cover.

On February 1, 2007, Robbins and Mitsubishi Heavy Industries (MHI) signed a contract with the CEC/Soma JV for two 6.5 m (21.4 ft) diameter EPBMs, back-up systems, and cutting tools. The machines were manufactured by Robbins using components from the U.S., India, and China.

On May 15 2008, the first of the two TBMs was launched from an 18 m (60 ft) deep shaft at the Jor Bagh station site. The machines bored parallel 2.0 km (1.2 mi) tunnels connecting the Udyog Bhawan and Green Park areas in New Delhi, as part of the BC-16 contract. The second machine was launched from the same site during the last week of June 2008.

Geology

The tunnels ranged from 8.6 – 14.0 m (28 – 46 ft) below the water table in sandy silt, silty sand and gravels.

Machine Design

Both EPB cutterheads featured a 55% opening ratio to allow a smooth flow of muck and to avoid clogging the cutterhead. The machines used several types of tungsten carbide bits for boring in soft but abrasive ground and shaft-type screw conveyors to remove water-bearing muck. Continuously erected lining along the length of the tunnel consisted of reinforced concrete segments 275 mm (11 in) thick.

Tunnel Excavation

On September 29, 2008 the first of the two Robbins EPBMs completed its initial bore of 1.0 km (0.6 mi), holing through into the cut and cover Race Course station site. High advance rates of 19 rings installed per day, together with over 90% average availability, contributed to the fast completion.  The machine was then dismantled in a reception pit and transported by road to the other end of the 318 m (1,000 ft) long Race Course site, where it began the second half of its bore to the contract boundary at Udyog Bhawan station. During excavation, the machine achieved a project record of 168 rings, or 202 m (663 ft) in one week—faster than any of the 14 other TBMs working on the project.

By April 2009, all four drives initially planned using Robbins machines were complete. Due to scheduling constraints, Continental Engineering Corporation (CEC) opted to use one of the Robbins machines for a fifth, approximately 567 m (1,860 ft) long drive from AIIMS to Green Park station sites. The fifth and last drive broke through on July 14, 2009.