Metro rail: 3 months to build each 2-km stretch

Metro rail: 3 months to build each 2-km stretch
New Indian Express

BANGALORE: The management of laying the foundation caps and raising columns for girders will have a bearing on the time taken to complete the 36-km metro rail. The construction is supposed to cause minimal inconvenience to citizens.

According to Bangalore Mass Rapid Transit Rail Limited (BMRTL) engineers, erection of a girder requires at least seven days.

Executive engineer Yashavanth Chavan said, ‘‘The process begins with BMRTL acquiring 3.5 metres from the centre of the road, on either side. Once we have a barricaded square, we will construct a ‘bored cast in pile’, which basically acts as a foundation for girder columns.We dig in four 15 metre deep holes and fill them with reinforced steel and concrete. These will act as four legs for a slab called the pile cap. The pile is earthquake resistant.’’

The next stage is the setting up of the pile cap, where a strict deadline has to be maintained. ‘‘The pile cap is cast across the pile group (the four legs) and is five metres below the road level. Once set, the cap is ready to take the load of girder columns. This work should take four days.’’

Executive engineer Keshav Prakash said the construction of the metro columns would be done in two-km stretches and traffic would be affected for two to three months at a time.

‘‘There will be 18 columns every two km. Since only seven metres of the main road are occupied, traffic will not be affected. In the piling stage, work will begin in the evenings,’’ he added.

‘‘The columns will be transported from the off-site area and set up at night. Each column 1.5 metres wide and 5.5 metres high is laid,’’ he said.

Prakash added that the real challenge is in piecing the girders together. ‘‘This process takes at least two nights. Once we put one girder on top of the column, it is necessary to connect eight more girders to reach the next column. Each girder’s width is about 9.8 metres. We use a material called epoxy to bind these girders. After completion of the 36 kilometre girder line, we will lay the rails. We wish to complete all this in five years,’’ Prakash said.

The construction begins in July and progresses through the monsoon. However, BMRTL officials are still sorting out how to deal with the weather