Rebuilt domain interchange bound 4 tracks not long after renewal ashfalt
showed signs of breaking up only breakdown R10 and line officer vehicle's
travel through this stop. certainly not as strong as concrete!!!!!!!
On Wed, 11 May 2022, 2:34 pm Hal Cain, hegcain@...> wrote:
> I took a look (by Google Streetview) at the surface in Keilor Road,
> Essendon, There, too, there are signs of cracking of the bitumen surface
> along the rails, though not as bad as in Bridge Road.
> I looked also at the track in Swanston St, between Grattan St and Victoria
> St, the first instance (as far as I'm aware, after 1920s/1930s cable track
> relay) of bitumen over crushed-rock over concrete-to-sleepers). Here the
> surface looks pretty stable, though it has not been subject to the heavy
> road traffic loads of Bridge Rd.
> For interest (partly because I watched it being laid, these many years
> past) I also looked at the bitumen-surfaced section in Cotham Rd, Kew,
> around Belmont Avenue, which was a trial section to establish whether a
> bitumen finish over mass concrete would make mass-concrete tracks less
> noisy -- the conclusion was that it didn't (and surely that could have been
> known by observing the track in Royal Parade and in North Melbourne and
> South Melbourne, where the same technique was employed? But they weren't in
> Kew or Camberwell...). Nor has the surface proved immune to cracking and
> damage, though I notice work has been done to seal over the surface cracks
> and keep water from penetrating.
> From my own observation, and (unsystematic) reading of manuals about road
> construction and surfaces, it looks to me as if bitumen road surfaces on a
> uniform base wear well, but when the base material is not uniform (as when
> part of it is slightly compressible (crushed rock, if not very heavily
> compressed by rollers and/or vibrating consolidation) and part of it is
> inherently inflexible (steel rails or reinforced concrete) then the areas
> where the traffic loads occur will wear much faster than elsewhere, because
> they move differently under load); this allows cracks to form, and these
> cracks allow water to enter, and that water helps to break up the
> bituminous load-bearing layer.
> It looks to me as if the bitumen-over crushed rock/aggregate over
> concrete-embedded sleepers is OK for light or moderate traffic, but for
> heavy traffic (such as Bridge Rd and, probably, Keilor Rd, and no doubt
> others that I haven't inspected, with a high proportion of heavier
> vehicles) it may not be adequate. By "heavy traffic" I mean heavy goods
> vehicles, not dense car traffic).
> Hal Cain
> in Hobart, Tasmania
> out of reach of personal observation of Melbourne tracks
> On Wed, May 11, 2022 at 11:14 AM Mal Rowe mal.rowe@...> wrote:
>> On 08/05/2022 13:10, Mal Rowe wrote:
>> > The strength and finished surface are starting to show some problems.
>> As promised, I went out to get some pics of some problems with some of
>> Melbourne's tramways renewed using the current technique.
>> The technique involves concrete to sleeper height, then crushed
>> rock/concrete fill to just below rail height and topping off with bitumen.
>> It mostly works well, but there are at least a couple of places where
>> problems with the road surface have emerged.
>> The two attached pics show Bridge Rd Richmond where there is very heavy
>> road traffic. The use of "Vienna stops" in this location concentrates
>> the motor traffic on the tramway section of the road. Most motorists
>> avoid going up and over the kerbside lane. It looks like the crushed
>> rock has not been stable enough and the bitumen surface is breaking up.
>> The tramway is fine - just the road surface is failing.
>> The other location I have noticed problems is in Dawson St Brunswick.
>> The section of roadway outside the tram rails is quite uneven - driving
>> along it in a car one notices 'long period corrugations' that give a
>> bumpy ride.
>> Getting the crushed fill to pack down is tricky - the small roller that
>> is used (see: https://tdu.to/i/80550 ) is probably not able to do the
>> job properly.
>> Mal Rowe - grateful to Warren Doubleday for the 'heads up' on Bridge Rd.
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