Created on : December 2011 CASE STUDY CASE STUDY 17 Strengthening of Metro Track bed, Kolkata The ballast less track of Metro Railways Calcutta is basically rails laid over R.C. concrete bed by means of bearing plate and rubber pads. The track bed known as second pour or levelling pour concrete was laid on the raft of the box of the Tunnel at a later date. When track was opened for service, it was noticed that with the increase in traffic density and speed above 50 kmph, the track was sinking in certain stretches of about 500 m in length, between Kalighat and Jatin Das Park Station. Thorough investigations were made and found that there was a fine gap due to separation between the raft and second pour concreting. The underside of the track bed was being pulverised due to constant

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