Re: Cleaning Ballast - Why do they need to do this?

["Ben Staples" <98711576@feline.hawkesbury.uws.EDU.AU>]

C. Dewick <craigd@lios.apana.org.au> wrote in message

**SNIP**

> >The requirement for Ballast is to keep the track bed dry and the sleepers
dry.
> >For concrete sleepers this donsn't realy matter, but you still need to
keep the
> >track bed dry and free of water.  Ballast is a good way of doind this,
but if
> >the ballast is dirty then the water will not drain away.

You might find ballast is also used to distribute the load of passing trains
more evenly then laying the sleeper directly on the sub base. Clean ballast
will also allow you to maintain good top and line.

> >Same thing applies to roads you need to keep the sub base dry or the road
will
> >crack and stuff up.
>
> >Having a wet track base will result in movement of the track base and you
will
> >get "speed hump" tracks and do more damage to the trains and tracks.
>
> Track laid with concrete instead of timber tends to 'pump' more on soft
> sub-roadbed because the concrete is *much* heavier than timber, and so any
> seepage of fluid from below the track is accelerated more than where
timber
> has been used.

I've been led to believe that the more exasperated pumping caused by the
concrete sleepers is due to their increased rigidity as complared to timber
sleepers, not purely their weight, though I admit they're quite heavy.

Ben Staples