Mumbai got its tallest tunnel at 11 meters for which close to 50000 kgs or 50 tons of explosives were used to dig it. On Tuesday this 320 meters long tunnel was dug while another 430 meters tunnel was already ready. This tunnel is part of the Mumbai-Delhi Western Dedicated Freight Corridor that is expected to be partly ready by next year.
The location is close to the Mumbai-Ahmedabad National Highway and a few kilometres away from the Virar railway station. On Tuesday afternoon, the engineers from Dedicated Freight Corridor Corporation of India (DFCCIL) reached the final stage for opening the belly of the 45-50 meters tall hillock. A web of explosives was wired on the hillock that had to be blasted open using a controlled explosion. Unlike the underground Mumbai Metro-3 project, where tunnel boring machines are used for tunnelling; here the railways are using explosives.
“The last 3 meters odd thick wall was remaining that had to be opened up for creating this 320-meters long tunnel. We used 200 kgs of explosives for the purpose of controlled blasting. We used the conventional method of using explosives as use of TBMs would have been a costly affair. There is another 430-meters long tunnel on the south end which was dug open early this June-July,” said a senior official from DFCCIL.
Before the blast took off, the space was barricaded and people were standing 150-200 meters away from the site. As part of the countdown, sirens wailed twice as an indication of the explosion to set. Then using a remote control, the hillock was blasted open. Several litres of water got accumulated inside the tunnel after the explosion, which used to be seeped during rains, over the years.
Soon after, the light at the other end of the tunnel was visible and thus Mumbai got a new tunnel on the western part of its metropolitan region after years. The engineers said that the height of the tracks from the roof of these two tunnels would be 11 meters or so which is the tallest ever. The average height of the tunnel from ground level is around 5.3 meters. The DFC is meant to transport double freight trains at high speeds that would be powered by power cables supplying electricity of two 25000 volt lines.
Now that the tunnel has been created that is around 5 meters in height, the engineers will dig further down all the way to ensure that 12-13 meters of height are reached from the top. They will also level the entire path of both the tunnels and their approaches. This rail line runs parallel to the National Highway and then there is a perpendicular road connecting it with the Virar railway station.
The authorities will construct a road overbridge here for vehicles while the freight corridor will pass perpendicular to it towards Vaitarna. Simultaneously they will cover the sides of the hillock with wire mesh to prevent it from falling. On the JNPT-Vaitarna stretch, there will be 25 major bridges, 5 major roads under bridges, 194 minor bridges, 11 road over bridges and 9 viaducts. In the coming months, the girdering on one of the viaducts passing Ulhas River will be started. They have collected 14.50 lakh cubic meters of stones have been generated from this blasting work which will be used to strengthen the tracks.
The western DFC will separate freight and passenger traffic to increase the speed of freight movement as it will be used to transport fertilizers, food grains, salt, coal, iron & steel and cement. The Western dedicated freight corridor will cover a distance of 1483kms of double-lane electric track from JNPT to Dadri passing through Vadodara, Ahmedabad, Palanpur, Phulera and Rewari. The important stations that will come across the corridor will be Phulera and Marwar Junction in Rajasthan, Palanpur, Amli Road, Makarpura, Gothangam / Kosad in Gujarat and Vasai Road in Maharashtra.
It will have special head-hardened (HH) 250m-long rails welded using Flash Butt welding machines. The axle load of the track will be 32.5t compared to the existing 25t axle load used on Indian rail tracks. The trains running on the Western DFC will be 7.1m-high, 3,660mm-wide, and between 700m and 1,500m-long. They will have a carrying capacity of 15,000t each.
