MAKING OF A Metro
The Engineering And Logistical Challenges Involved In Building An Overhead
Transport Route In The Suburbs Are Daunting
Sunil Nair
An overhead mass transit route spanning 12 kms across densely developed
suburbs in Mumbai is what most people would call a pipe dream. If it’s a
flyover (like the one over JJ), you know you could throw in some sharp
curves to negotiate the gaps between buildings. If you ran into a wall of
highrises, you may even tweak the plan a bit: make drivers climb down to a
lower level at a traffic intersection, take a few turns, get on to another
bridge. But that’s if they were driving; what would an engineer do if he
needed to maintain a straight line and a uniform level for an elevated track
running on power through a congested stretch?
Railway engineering doesn’t allow a designer the luxury of a small
radius of curvature or a steep gradient. Which means, a metro train can’t
turn around a Seven Bungalows bend at 45 degrees and whizz down a sharp
incline. It has to maintain speed and height for passenger safety and
comfort and optimal power usage. At the same time, it’s got to shave off travelling time
considerably – remember, that’s the rationale for spending so much money. So
think of an unobstructed alignment starting at Versova and going all the way
to Ghatkopar on the eastern flank, which could cart five lakh commuters
daily in AC comfort, doing each trip in not more than 21 minutes. Now you
have some idea of the challenges facing the Rs 2,300-crore Mumbai Metro
project.
To start with, Reliance Energy has hired a range of international
consultants to meet the four-year deadline. Parsons, Brinkerhoff (from the
US) and Systra (France) are among those on board along with officials of
varied backgrounds from Railways and Delhi Metro. Holding the team together
is Krishna Prakash Maheshwari, 38, a mild-mannered man whose engineering and
MBA background should stand him in good stead.
A range of surveys have only served to underline the daunting nature of
the task. More than 6.5 kms length of public utilities like phone cables,
sewage lines, gas pipes, would have to be untangled and shifted before the
team even begins to lay the foundations. In fact, that alone should keep
Mumbai Metro
One Pvt Ltd on its toes
for the next five months.
The plan is to deploy trenchless technology. Pits are to be dug at different
points and micro-tunnelling carried out to build alternate routes for sewage
and phone lines to pass through. “We now have a complete map showing the
position of all the utilities running through this area,” says Maheshwari,
director, Mumbai Metro.
It must have taken a lot of doing although he doesn’t seem to be the kind
who likes to gloat. Gas and phone companies in the city, the civic
corporation, the power majors, they can at best be described as working at
odds with each other. They take turns at digging up roads, laying and
relaying and shifting lines around according to each one’s convenience. In
all these years, Mumbai has never had a master plan that showed the exact
positions of all these networks. The map compiled by Mumbai Metro using
geo-penetrative radars will now hopefully serve as a reference point for
everyone. Challenge number 2. They have to build overhead tracks along the
centre of the road passing over 22 major traffic junctions.
Along the way, the line will also transcend Andheri station and Jog flyover on Western
Express Highway. Minimum ground clearance would be about six metres but at
some points, the coaches would be moving at an altitude of 20-25 metres, the
height of a five-storey building. Engineers are planning to string together
pre-cast concrete girders propped up by monolithic pillars or piers to build
the viaduct on which the metro will move. “This method can provide the
flexibility needed to erect the transport system over uneven terrain and
busy traffic,” says S C Gupta, exdivisional railway manager, now
Construction Head, Mumbai Metro. Trials have already been carried out to
check if hydraulic trucks can be used to haul beams 30-90 metres long from a
depot at Wadala to each site. “The streets are narrow in places. So we used
a trailer with 14 axles to move a long girder from the Bandra-Worli seaface,
just to check whether it can be done,” said Maheshwari.
Quick delivery of material and equipment is the key because the Metro team can ill-afford to trigger a controversy over inconvenient traffic diversions. They are hoping
to barricade off not more than 9-10 metres on every road over which the
viaduct will be built, and are setting a 6-8 week deadline to clear out
barriers in any given area. It’s the cut-and-cover method of construction
pioneered by Delhi Metro, which they plan to use to keep ahead of schedules.
“With a power project or a cement unit, you can stop work for about 10 days
because it’s at a site and doesn’t affect external factors. Here, we don’t
have that luxury,” says Maheshwari.
If the groundwork is any indication, the Metro team has most angles
covered. Soil analysis is complete – and it shows how tricky the terrain can
be. In the hinterland where the bedrock is stone, work should be quicker.
But closer to the coast, they will need to burrow deeper through marine clay
and erect taller pile foundations. Then there’s the business of resettling
those whose shops and houses will need to be demolished. The government is
handling that, but it could still slow down the project. And finally, they
will need to set up power and telecom networks and run safety tests on
passenger coaches. You might call the fouryear deadline unrealistic, but the
Metro team is hoping to beat it.
Phase I:
Versova to Ghatkopar
Phase II:
Charkop to Mankhurd
Phase III:
Colaba to Bandra FUTURE RIDER Cost: Rs 2,300 crore Versova-Ghatkopar metro:
12 kms Travel time: 21 minutes Standard gauge running on 25 KVa 4-coach
trains to carry 1,500 passengers on each trip Total traffic: Up to 5 lakh
passengers daily
COACH DIMENSIONS
Length: 22 metres Width: 3.6 metres Height: 3.2 metres TARGETS MET, PLAN ON
TRACK
Topographical survey completed to decide alignment for the route
Soil analysis carried out to investigate terrain conditions along the route
Consultants Parsons, Brinkerhoff and Systra brought on board
Energy-efficient design finalised to run trains on 25 KVa network
Plans ready to build a concrete viaduct supported by pillars
Contracts to be issued for micro-tunnelling work to shift gas, phone lines
Trials done to check if 90-metre-long girders can be transported to sites
Metro team targets four-year deadline to commission the project