Railways use unique pulley and winch method to place girder to dodge water pipeline that runs dangerously close
The work on the Nahur bridge was challenging, making the railways prepare for it for the past six months
Work on the first phase of widening of Nahur bridge over railway lines was completed in an operation on Saturday night. Railway officials said the work to install the girders was challenging due to lack of space in view of a water pipeline close to the site and the narrow road below. To ensure placing the girders safely, officials prepared for six months to work out a unique method. Bridge work is likely to be completed before the monsoon.
The Nahur road overbridge, which originally had four lanes, will get two new lanes on either side, as per the plans. However, as the bridge runs over railway tracks and several utilities needed to be shifted for the extensions, the railway officials had to plan a process to install the girders without inconveniencing train or traffic movement.
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Railway officials connected two girders first and then placed them on a temporary bridge (in brown) before putting them in place
Before launching the girders, which are 72 metres in length, officials first connected two of them for one lane. This brought the total weight to 432 metric tonnes.
Now, due to the adjoining pipelines, bridge, space constraint and the size and weight of the girder, it was not possible to launch it using a crane. So, officials specially designed the pulley and winch method, first of its kind on Indian Railway.
The preparation
A railway official said, “Launching the girder safely required the creation of one small base bridge. The girders were placed on this by using a 700 metric crane. The preparation of the bridge and placing girders took time. Then four 63-mm thick solid plate paths were created over the temporary bridge and railway track. We prepared a state-of-art sliding skids arrangement on these paths using runners, wooden blocks and guide angle assembly kit. We used 14 such skids on each path. We also used special material to reduce friction and to ensure the material is not crushed, which is necessary to skid heavy girders.”
The girder was then pushed over the railway tracks
“Once the entire arrangement was done, it was connected with a winch and pulley system. A winch with a capacity of 25 metric tonne and speed of 2,500 mm per minute was used to push the girders on skids. This very elaborate and precise preparation had to be done to make it safe. Since it is a suburban area, a lot of utilities needed to be relocated,” he added.
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Final step
After all the preparation was done, railway officials, in a 3.5-hour operation, pushed the girders over railway lines. Now, the girder needs to be shifted to the side and the three others will be launched in the same manner. The operation is likely to be completed in the next two-three months. Once the new lanes are ready, the central portion of the bridge will also be recreated.
Most of the girders required for the bridge have been fabricated and are at the site. While the railway is working on the bridge, the approaches are being worked on by the BMC. Two lanes will be added at the CSMT-end and two at the Thane-end in a phased manner.
‘It was challenging’
“It is a challenging task and the unique method we used to skid the girder was used for the first time on railways. It took about six months to prepare for the push. The work involves widening of the existing four-lane bridge to eight-lanes and also strengthening the existing bridge. More such girders will be placed, and the entire work is expected to complete by July 2023 if things go as per plan,” a senior rail engineer said.
He added, “Since this is a suburban area, a lot of utilities including cables, gas pipes etc had to be relocated and it was possible to get this done with the active cooperation of local MP, BMC, Mahavitaran and the police teams.”
The Nahur road overbridge is one of the crucial feeder routes as it links the proposed Goregaon-Mulund Link Road and the existing LBS Road in the west to Eastern Express Highway in the east over rail lines, and also Navi Mumbai at Airoli junction across the creek. The stretch over the rail lines at present is very narrow and a real bottleneck with immense traffic jams. The authorities are converting footpaths on both sides of the road into vehicular ones by levelling it.
With this road bridge widened to eight lanes and a new one proposed over rail lines at Bhandup, east-west connectivity in the eastern suburbs will improve significantly. The half-km bridge to be built at Bhandup at a cost of R106 crore will help motorists move from LBS Road to Eastern Express Highway via internal Veer Savarkar Road in Bhandup East.
July
Month in 2023 when the work is set to be completed
3.5
Time (in hours) it took to push the girder in place
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