Assessment of Ballast Requirements
The requirements of the ballast should be assessed separately
the deficiencies existing in the track as well as those arising out of
overhauling, through packing and deep screening,
adequate cushion for mechanical tamping, and
extra cushion while converting into LWR.
The ballast required for
maintenance purposes is estimated by assessing the quantity approximately, if
necessary by a survey, over every 1 km of rail length. Care should be taken to
ensure that the cores under the sleepers are not disturbed.
In the case of deep screening,
the ballast required for recoupment and providing a standard section should be
assessed by deep screening the ballast on a trial basis. For this, full depth
screening is done for a length of 2-3 sleepers at every 0.5 to 1 km interval.
In this case, the screening is done under the sleepers as well. The quantity of
ballast required for deep screening is roughly taken as 1.5% of the existing
quantity of ballast based on field trials.
The quantities assessed above
will be the net quantities of ballast required to recoup the deficiencies or to
provide required profiles/sections. These net quantities of ballast may be
enhanced suitably (say by 8%) to arrive at the gross quantities of ballast
needed for the purpose of procurement in case the measurements are proposed to
be taken in stacks or wagons at the originating station.