Cranes reach into Delhi's belly

Delhi is one of the world's oldest cities, with archaeologists dating the earliest settlement on the site to more than four millennia ago, and one of the biggest, with a population of 17m in the city centre and 27m across the wider municipality. It is India's capital, and will host the Commonwealth Games in 2010.

As India has advanced, both technologically and in terms of its population, the argument for an efficient mass rapid transport system in its capital city has become more and more pressing. The Delhi Metro Rail Corporation (DMRC) was established in 1995, with the aim of building a world-class metro, and the first section of the system came into operation in 2002.

The three lines opened in 2002 ('Phase I') include 65km of track, with 13km running underground, and 59 stations. Work is currently underway on Phase II of the project, which will extend the system by 120km, and add 80 stations. A further two phases of construction will be completed in 2015 and 2020, by which time the metro will cover more than 400km of track.

Phase II of the project involves two new stretches of line. The first, 21.16km, stretch of Phase II will connect the city centre, known as the Central Secretariat and home to India's federal parliament, to the outskirts of the city. This section will cost INR40.12bn (USD1bn), and will include 15km of elevated track and 5.16km of underground track. The main contractor and civil engineers are Senbo Engineering, ITD-ITDCem JV and Gammon India.

The second stretch of line will extend the metro out into Delhi's suburbs, known as the National Capital Region. This 22km route will cost INR2.5bn (USD610m) and be made up of 14km of underground tracks and 8km of elevated tracks. The contractors for this section are Larsen & Toubro, CEC SOMA JV, MTG (a joint venture collaboration of L&T, DV Deck, and IRCON), Samsung and Shimizu. The project construction companies own their own cranes and operators.

The metro has brought immense social benefits to the city of Delhi. With 650,000 commuters using the Phase I lines every days, it has removed thousands of polluting vehicles from city roads, making a significant positive impact on the pollution level of the city. According to estimates by Central Road Research Institute of India (CRRI), the central government road research institute, the metro had replaced 40,000 vehicles, including cars, buses, two wheelers, auto-rickshaws, by the end of 2007.

The CRRI has estimated that the environmental and social benefits of Phase I will help recover the full INR10.57bn (USD2.64bn) cost of the project by 2013. The CRRI estimates the metro had already helped the city save INR20.72bn (USD520m) by the end of 2007. These benefits are the result of passenger time saved, fuel cost saved, reduction in capital and operating costs of vehicles, reduction in environmental damage, accidents prevented, and less maintenance cost on infrastructure.

With the completion of the second phase, the metro will carry up to two million passengers per day. This will make a further dent on the share of vehicle population. But above all, it will serve to be an example of a technically complex infrastructure project built efficiently, all inter-linking the residential, commercial and industrial areas of the capital city along with its outskirts.

The most obvious challenge presented by the project is its size and complexity. The Phase II project, including the two stretches under construction, is a complex project in itself. The elevated track sections will be built over road crossings, railway crossings and flyovers at 19 different locations across Delhi. In some places, spans will be more than 34m long.

The longest span of the metro so far will be built over the high-density railway line at the city’s outskirts, on the 21.16km stretch between the Central Secretariat and the city's outskirts. The span will be 100m long with supporting spans of 75m on either side. An important construction component of the project is construction of one of the tallest piers, 19m high.

The construction work has to take place in the capital city, with more than 14m people and 3m cars potentially affected by the work. Large amounts of material must be transported into the city, causing significant disruption.

However, having world class project management knowledge at its disposal, gained from global consultants during the construction of its first phase, DMRC is confident of completing the project ahead of schedule. The organisation has earned accolades from home and across the globe for completing the 65.1km Phase I project two years and nine months ahead of schedule. DMRC managing director E Sreedharan was chosen by CNN-IBN (the Indian partner of the CNN news channel) as 'Indian of the year' for 2007.

For the crane crews working on the project, there have been some specific challenges. Space at job sites is limited; while rough terrains may have been easier to use, they are in short supply in Delhi, so crawlers have been used instead. RTs have been diverted other projects in India, particularly to sugar mill construction projects in northern India, which is booming, Jamnagar, Gujarat, western India, maintaining India's largest petrochemical plant owned by Reliance Industries, plus brownfield and greenfield construction projects across India, and industrial plant construction in and around Delhi.

In an effort to keep project costs down, DMRC's rental charges are less attractive than other industrial projects, particularly in an environment of more work than rough terrain cranes. Also, many rental cranes do not have automatic safe load indicators installed.

J K Shukla, Phase II construction manager for contractors Larsen & Toubro, says, “Since the project is taking place in the centre of the city, the construction sites have space constraints. As crawler booms can't be retracted, the crawler cranes have to be operated with utmost caution, so they do not hit nearby buildings during their slewing or lifting operations. This is a big challenge, since many of the lifts have to be done from the roadside. There is always apprehension that the crawlers might damage the road surface.”

Some parts of the project are taking place close to key government ministries in the Central Secretariat district. Many of the buildings here were built prior to India's independence, sixty years ago, and could be subject to damage from underground vibrations. To protect against this, and to allow for subsurface tunnels to be built quickly across the city, the DMRC is using a system known as 'cut and cover'.

The 'cut and cover' method used to construct tunnels on the project calls for a large number of cranes. On cut and cover tunnels, engineers dig an open excavation, in which 13t universal beams are laid horizontally. At the edges of the tunnel, piles are placed, and more universal beams laid vertically on top. The 8t vertical beams at the base of the tunnel must be lowered 16m.

The entire process of laying the beams is being undertaken using crawler cranes. At one of the underground sections, under the 5.16 km stretch, at least three Telcon Tata TFC 280 crawlers can be seen working. The cranes have a lifting capacity of 75t each at 24.39m basic boom. Under the 14 km underground link, at the Central Secretariat, three Telcon Tata ALC 955 crawler lattice boom cranes are working. The cranes each have a lifting capacity of 75t with boom extended double the basic length to 30.5m.

Crawler cranes are also being used by DMRC on the elevated stretches. Here, they are unloading 20t–23t pre-cast concrete girders from trailers for the superstructure. The girders are then lifted up by 70t–72t capacity hoists, ready to be installed into the super structure. The cranes are also being used to install steel formworks used to construct the piers.

Although crawlers are not the first choice for the job, they have some advantages over RTs. First, operators jerk sticky concrete out of the bucket that they lift by releasing the brake momentarily so that the hook free falls. Only crawler cranes are built for this kind of stress. Second, the 4-5m crawler track spread takes up about a metre less space than an RT on outriggers.

On the other hand, their swing radius is much greater than RTs, so extra care must loads need to be slewed. And crawler tracks can damage the worksite surface when they are moved.

Workers on the cut and cover worksite at Central Secretariat deal with the consequences of site congestion every day. The work site measures 25m across, from one barrier to another. Inside is a 20m hole for laying strutting beams, with a gap of about 3m on either side. On one side of the site is housing for senior government officials; on the other is a road. For ease of access, the crane works from the roadside. In order to reach the entire job side, the crane needs a working range of 18m to the midpoint of the strutting works. That means that the crane hangs 5m outside the work site into the road. All of the crane's work lifting and placing the beams happens when workers close the road. Stopping traffic is particularly difficult because much of the vehicular traffic holds VIPs, including senior ministers. Also, trees planted by the road further obstruct the crane. The proximity of road, trees and nearby buildings all pose hazards for crane slewing operations, particularly because the crane's boom cannot be retracted.

Cranes are also working in fabrication yards, for a number of different contractors at job sites along the extension. A brand new Kobelco RKE-500 rough terrain, with a lifting capacity of 51t at 10.2m, and a new 70t Tadano GR-700 EX rough terrain, are being used to load and unload universal beams at contractor Senbo Engineering Limited’s fabrication yard under the 5.16km link.

Larsen & Toubro has a couple of cranes from Indian manufacturer Action Construction Equipment. The 12t ACE 12XW cranes are working at the company's fabrication yard for lifting of reinforcement rods, construction equipment, concrete pumps, and generator sets. L&T is constructing two underground stations under the 22km stretch.

Another use for the yard cranes is to place construction site barricades, to segregate the construction site from the public.

Lifting logistics

As cranes are playing such an important role in the project, and deadlines are so tight, DMRC has put a programme in place to minimise downtime. DMRC has laid down elaborate stipulations for cranes working on the project in excess of normal rules in Delhi. Cranes that don't meet the standard will be banned from extension job sites, and will attract a stiff penalty for contractors.

According to the work contract, the DMRC could punish contractors that overshoot their deadlines by deducting money: this is part of the 'Liquidity Damage' (LD) clause. But it prefers not to, partly to keep a cordial relationship with contractors. To ensure the project is done on time, chief project managers meet weekly with contractors and consultants. The DMRC also advises contractors in advance of important project deadlines.

DMRC has appointed test agency International Engineering Co to examine cranes before they are allowed on the job site. The agency conducts proof load tests, and ensures the cranes are fitted with safe load indicators, and then checks them twice a month. It also checks the manufacturing date of the machines, and quality of the wire ropes, brakes, winches, pulleys, and hoist. Crane riggers need to be qualified and signalmen need to be trained.

J K Shukla, construction manager, Larsen & Toubro, Delhi Metro Phase-2 project says, “The clauses are good but given tight project completion schedules, we require more cranes. However, it is difficult to find more cranes, as there are no new cranes available and cranes belonging to the rental companies do not completely satisfy DMRC’s stipulations. In such a situation, we have to operate with our existing cranes only by undertaking periodic maintenance.” In most of DMRC’s projects, cranes are owned and operated by the main contractors themselves.