Micro-tunnelling comes to Mumbai

The city just got its first taste of hi-tech tunnelling when Patel Engineering cut through the surface rocks at Jogeshwari (a western suburb) to install a line to supply potable water there.

Patel Engineering recently won a contract to dig 10 micro-tunnels across the city. The project will be executed over 18 months in collaboration with Michigan Engineering.

The 120-mt long micro-tunnel was dug across the Western Railways lines today as part of the micro-tunnelling project of the Municipal Corporation of Greater Mumbai (MCGM). The tunnel, fitted with a 1.7-mt diameter steel pipe, will be used for supplying drinking water from Jogeshwari East to Jogeshwari West.

The horizontal drilling took 20 days to complete. In micro-tunnelling, the steel pipe being laid moves simultaneously with the machine and is completely automated. Both pipe steel and concrete pipes can be laid using the technique.

The technique is cost-effective as it avoids traffic disruptions and also circumvents the need to dig roads and highways. To ensure safety, the tunnel is usually laid at a depth of 1.5 times the diameter of the tunnel. In this instance, the railways have specified that the tunnel for further safety should be a steel tunnel.

The corporation has identified 14 locations, prone to water logging during the monsoon, for the Rs 19 crore project. The project is expected to be completed by October 2006.

Given the current concretisation of roads, conventional means of tunneling (digging) could not be used for laying these pipes. This made way for micro-tunnelling, so that there are no traffic snarls.

Four of the locations the involvement of railways - Jogeshwari, Chunabhatti, Mahul and Mankhurd are in this section. However, the last two locations are yet to get railway's clearance.

The next locations for the project will be Ajgaonkar Chowk and Annie Besant Road in Worli. The latter will be a tunnel of 80 mt and the work is expected to start on Friday. At present, there are two machines-AVN 1500TB and AVN 1200T"� which have been imported from Germany. Sources said both the machines were imported at a cost of Rs 9 crore.

The other locations to go under micro-tunnelling include Haji Ali Circle, LBS Marg, Worli Passport Office, Versova pumping station and Bunderwadi.