Explain Measured shovel Packing
Measured shovel Packing essentially consists of accurate measurements of track defects particularly the unevenness and voids caused in the course of service and attending the same by placement of measured quantity of small sized stone chips under the sleeper to bring the track to predetermined levels. The compaction of chips is obtained by passage of traffic. The extent to which the track is required to be lifted is calculated by measuring the longitudinal unevenness in the track after applying corrections for cross levels and voids under the sleepers. The longitudinal levels are measured with the help of optical instruments called viseur and mire and the voids under the sleeper bed are assessed by a ball ended rod called canne a boule and checked with the help of a mechanical device called dansometer. The track is lifted by 40 mm by special type of non infringing jacks and a measured quantity of stone chips is then placed in the sleeper bed with the help of special type of packing shovels. The jacks are than tripped off and the alignment is finally corrected. It may be clarified here that track to be maintained by MSP needs a well settled ballast cushion bed and stable formation and such MSP should neither be used immediately after track renewal and deep screening nor after renewal of a large number of sleepers nor when the lift required is more than 80 mm.