Yarra Glen Trestle

K-Class · Posted: Tue Oct 14, 2008 9:37 am

Recently I was out at the Yarra Glen trestle to take photos and measurements for the model I plan to build and noticed that the majority of the bridge(s) is built with 4 piles per cross head but mixed in with this are a few 2 piles per crosshead and a couple that have 3 piles.

Does anyone know why there is a mix of construction types within the same structure for no apparent reason.

wongm · Posted: Tue Oct 14, 2008 9:46 am

Could you see any relationship between number of piles and other attributes? Height from the ground? Some of the piles more rotten than others? Were they in groups or alone? Maybe they added more piles after the originals rotted, or perhaps the ground was softer in certain spots.

Marcus Wong

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perks · Posted: Tue Oct 14, 2008 12:26 pm

Reason is fairly simple, and is common to many early (pre 1900) trestle bridges in victoria.

YG trestle was originally built as a 502 x 15ft span bridge, with 2 pile piers and satellite outers on the bracing. As the line was upgraded to take heavier locos in the early 1900's, extra piles were added as required. This was initially outer piles on corners, but was progresivly added to up to the 1950's.

In the 1930's, with the first round of pile replacements becoming due, the maintainance on the bridge was too large to justify and the decision to fill in a large portion of the bridge was made. The bridge was split into 6 segments and backfilled with the assistance of a mechanical steam shovel. Extra land was purchased so that sufficient soil could be piled up to for the embankment. The soil was packed under the existing bridge until just below the deck. The crossheads and beams were then lifted, and track layed back onto the new soil. The new abutments were made with crossheads and beams recovered from the old bridge. Google Earths view of the bridge shows the bits which the steam shovel dragged the soil from, you can even see the staggered breaks in the pit, where it changed sides.

Works were almost finished when major flooding occurred in the valley in the mid 1930's this washed out another portion of the biggest segment, closing the line for 3 weeks. This segment was again filled with earth, and is the short join between the two biggest segments, 5 and 6.

As per VR practice, its still considered one bridge and keeps its old span numbers. Final numbers for Bridge 10 is 7 segments, segment one is spans 25-29(5), two is 120-124(5), three 203-213 (11 ), four 275-292(18 ), five 331-368 (38 ), six 378-434 (57) and seven 457-461(5).

This shows segment 7, still with 2 pile piers, modified to current drawings

This shows the end of segment 6, with both post 1936 4 pile piers and older satellite 2 pile piers. The closest pier (pier 430) shows the right hand side with original satellite and bracing, with the left having an outer pile.

This shows some of the varied spans that exist along segment 6

This shows a span on segment 5 not far from the yarra, with 2 piles in a raked formation. Not sure if this was a bridge gang "just because" change, but is certainly rare for the bridge, and the line as a whole.

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K-Class · Posted: Tue Oct 14, 2008 2:32 pm

Thanks for that info Perks. That does make sence now.

yarra1949 · Posted: Tue Oct 14, 2008 3:50 pm

If you would like to learn more about the trestle bridges of the yarra valley why not come up to the YVR and give perks and the others a hand to repair the bridges. Also learn the skills and knowledge in the art of timber bridge building and repair.

Ray Williams.

Mel · Posted: Fri Nov 07, 2008 6:12 pm

Bit of new wood and concrete foundations and off you go....