locations drain perfectly. You seldom find ideal drainage on either military or commercial lines.
The importance attached to achieving good drainage is pointed out in the rules of two
large commercial lines:
Cold is damaging only by reason of the water which it
freezes; therefore, the first and most important provision for good track is
drainage.
Drainage is of the first importance in track maintenance.
The remaining paragraphs of the section discuss why drainage is needed, how to obtain it,
how water pockets are corrected, why and how ballast is cleaned, and how side ditches and other
drains are constructed.
2.10.
NEED FOR DRAINAGE
Everyone becoming acquainted with track maintenance soon becomes aware that water is
track's greatest enemy. They learn that water splits rocks when it freezes, washes away roadbed
material when ice and snow melt, rusts track joints, rots ties, and sometimes in a spring freshet
washes away the entire track. They learn that adequate track drainage is of primary importance
in keeping a train operating. Pumping ties and water pockets result when track drainage is
adequate.
a. Pumping ties. As heavily loaded trains pass over an inadequately drained track, they
force the ties down into the ballast, pushing the ballast into the subsoil of the roadbed. After
each train passes, the resiliency of the steel rails lifts the ties up, leaving a hole under each tie.
After numerous trains have passed, this movement of the ties "pumps" water into the already
formed holes, and the water rots the ties.
If a section of track has several pumping ties, the track becomes spongy, uneven, and
unstable. The immediate remedy is to pack new ballast under the tie or ties. Although this
apparently clears up the trouble at first, it only adds to the difficulty in the long run. As the
ballast under each tie goes deeper, the subsoil is forced up between the ties, as figure 2.4 shows.
Not only is instability created but even the little drainage previously possible is prevented.
Furthermore, the holes are soon re-formed, and water pockets result.
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