Bridges and tunnels

[alan_fincher]

11 hours ago, Captain Pegg said:

Tunnels are a subset of bridges. They are long bridges.

Not sure if it has had a mention, but something like Dunsley Tunnel on the Staffs and Worcs shows as only 25 yards.

In my head it is clearly a tunnel, but hardly a long bridge, as huge numbers of bridges are far longer than that but would never be classed as a tunnel.

So I can't agree with your definition, I think!

[Derek R.]

Long bridges. Let's see; Severn, Humber, Orwell, QEII, Forth, Syney Harbour, Golden Gate . . .

[Captain Pegg]

3 hours ago, Derek R. said:

Long bridges. Let's see; Severn, Humber, Orwell, QEII, Forth, Syney Harbour, Golden Gate . . .

If you want to be pedantic then try a long overbridge.

JP

[Captain Pegg]

10 hours ago, alan_fincher said:

Not sure if it has had a mention, but something like Dunsley Tunnel on the Staffs and Worcs shows as only 25 yards.

In my head it is clearly a tunnel, but hardly a long bridge, as huge numbers of bridges are far longer than that but would never be classed as a tunnel.

So I can't agree with your definition, I think!

What I said was that you can't define the difference but that CRT as an infrastructure owner will have a criteria - probably based on length - by which they distinguish which are tunnels. There will be exceptions and Dunsley may be one.

JP

[alan_fincher]

2 hours ago, Captain Pegg said:

What I said was that you can't define the difference but that CRT as an infrastructure owner will have a criteria - probably based on length - by which they distinguish which are tunnels. There will be exceptions and Dunsley may be one.

JP

I doubt this, because most will have  been badged as a bridge or tunnel long before CRT existed, or indeed in the majority of cases long even before the waterways were nationalised, (with the obvious exception of any built since).

I would argue that most are badged as a "bridge" or a "tunnel" simply because they always have been probably, in most cases, from the day they were first built, and in many cases centuries ago.

I doubt the original criteria for naming was based solely on length of "bridge" or "tunnel", (but I can't prove it!)

Edited August 26, 2017 by alan_fincher

[Captain Pegg]

26 minutes ago, alan_fincher said:

I doubt this, because most will have  been badged as a bridge or tunnel long before CRT existed, or indeed in the majority of cases long even before the waterways were nationalised, (with the obvious exception of any built since).

I would argue that most are badged as a "bridge" or a "tunnel" simply because they always have been probably, in most cases, from the day they were first built, and in many cases centuries ago.

I doubt the original criteria for naming was based solely on length of "bridge" or "tunnel", (but I can't prove it!)

I think the issues are different from the navigational and engineering perspective. I gave the probable technical distinction based upon having been repsonsible for a tunnel or two in a comparable environment.

The key point from an engineering perspective is that a tunnel has a different management regime. So it is important for CRT to have a set of criteria to determine what is technically a tunnel. From their perspective a structure could change from being a bridge to a tunnel or vice versa.

Historical descriptions won't make any difference to CRTs engineering  classification.

From a navigational perspective that doesn't matter. Ventilation is probably the key criteria.

JP

Edited August 26, 2017 by Captain Pegg

[Peter-Bullfinch]

Most of the long stretches of canal covered by bridges would appear to be the more modern wider ones taking motorways and dual carriageways. I wonder if the Trust puts the lengths down on any of their published maps of the system. 

I suppose to answer Ditchcrawler's note about the HS2 proposed bridges, the length of canal to be covered must be in the published plans somewhere or other.

[Derek R.]

13 hours ago, Captain Pegg said:

If you want to be pedantic then try a long overbridge.

JP

Then there's a bridge over troubled waters. Hardly pedantic . . . but clearly we're in the silly season.

[magpie patrick]

On 25/08/2017 at 22:07, David Mack said:

So what are Galton and Summit tunnels on that basis? Both were built to carry a road over the canal. But the canals had originally been built in deep cuttings to go through high ground.

If i were to be pedantic i would argue that they are navigable culverts. They are certainly not bridges.

I guess from a navigation perspective it becomes a tunnel when the experience is akin to navigating a pipe, si it would be a combination of constricted gauge and length 

[Heartland]

A bridge is a bridge, a tunnel is a tunnel. So what IS the difference?

A bridge spans a space, whether it is a waterway, road, railway or a geographical feature such as a valley or ravine. Width is variable, height is variable and the components of which ii is made is also variable.

Motorways have created wide spans of navigable waterways. For example the M65 that runnels parallel to the Leeds & Liverpool in the Blackburn and Burnley area with spans over the canal bridge no 114AA Enfield Green Bridge, 124A Molly Wood Bridge, 124B Halstead Bridge, 127C Gannow Green South Bridge and 143 Barrowford Bridge.

A tunnel is cut through the landscape and the key element is that it passes underground. Length again is variable, construction materials also vary. In the past it was stone, brick and sometimes the unlined rock was left to form the roof, sides and base. In modern times tunnels are made of concrete sections. The current Northern Line extension in London is using two Tunnel Boring Machines to cut two parallel bores that will be lined with concrete sections. The spoil from the cutting is taken back by conveyor to the Thames for loading onto barges. A similar practice happened with the making of Crossrail 1, now known as the Elizabeth Line.

With canal tunnels the bore is also circular or eliptical. There may be a towpath, height may be variable (eg Gorsty Hill) but again there are sides a roof and mostly importantly an INVERT. Lengths vary. Normally canal tunnels are named. During the canal building period construction involved the sinking of shafts and digging out the canal from the base, in a similar fashion to the practice of mining. Though not always. Telford used a cut and cover technique for Chirk. In the case of Ellesmere Tunnel 87 yards long it is numbered (57).

Whether modern LOCK TUNNELS should be considered as a separate entity is something to debate. Take for example Sellars Tunnel (355 yards) and Bates Tunnel (100yards) which were constructed on the Huddersfield to enable the navigation to Huddersfield to be boater accessible again. Another example is Tuel Lane Tunnel (114 yards) at Sowerby Bridge on the Rochdale.

Staying with the Rochdale there is Edinburgh Way Tunnel (121 yards) near Rochdale where the canal passes under the road system, roundabout ans A627(M) and made as a diversion to the original route.

Further into Manchester the M60 crosses at Bridge 76B which is also called M60 Tunnel, whether it should be is another matter of debate- but because it may be more enclosed might swing the naming towards a tunnel naming.

Can enclosure be a defining point and what ever is a agreed there will be exceptions. Such is the case of Little Tunnel Bridge on the Basingstoke!  

 

[Richard10002]

I'd say that bridges are built over things, and tunnels are bored through stuff. Where a deep ravine is covered for a large part of its length, such that it looks like a tunnel, but is built over, there will be some flexibility in naming and definition - it looks like a tunnel, but was actually something built over the ravine.

we tend to tunnel through stuff, and bridge over gaps.

[1st ade]

5 hours ago, magpie patrick said:

If i were to be pedantic i would argue that they are navigable culverts.

Round two - when is it a culvert (the watertight part of the navigation is cast in a single piece of concrete??) and when is it a cut - cut and covered or otherwise?

[magpie patrick]

15 minutes ago, 1st ade said:

Round two - when is it a culvert (the watertight part of the navigation is cast in a single piece of concrete??) and when is it a cut - cut and covered or otherwise?

From the online dictionary

culvert

ˈkʌlvət/

noun

 

1. 1.

   a tunnel carrying a stream or open drain under a road or railway.

    

   Which is not entirely helpful I'll grant you!

    

   However, in my experience of projects culverting something is the act of burying it in a tube - the channel pre-dates the tube it is put in, hence Galton and Summit Tunnels are very big culverts. To add to the confusion, some structures that most people would call bridges are actually known as box culverts by engineers.

    

    

[David Mack]

5 hours ago, magpie patrick said:

From the online dictionary

culvert

ˈkʌlvət/

noun

 

1. 1.

   a tunnel carrying a stream or open drain under a road or railway.

    

   Which is not entirely helpful I'll grant you!

    

   However, in my experience of projects culverting something is the act of burying it in a tube - the channel pre-dates the tube it is put in, hence Galton and Summit Tunnels are very big culverts. To add to the confusion, some structures that most people would call bridges are actually known as box culverts by engineers.

    

    

I still don't regard Galton and Summit as culverts. But that probably is a reasonable description of the structure that carries the Droitwich Junction Canal under the M5 - it was originally built for a watercourse and only much later used for the diverted canal.

But what about the corrugated steel tube that takes the Droitwich Barge Canal under the railway? That and the embankment above it replace an earlier railway bridge over the old canal line. So is it a bridge, tunnel or culvert?

 

[Derek R.]

Maybe it's an adit, and canals are gutters . . . When is a cut not a cut?

These precise definitions of what is either a canal, bridge or tunnel is really quite irrelevant when commonsense tells us all we need to know.

[Pluto]

6 hours ago, Derek R. said:

Maybe it's an adit, and canals are gutters . . . When is a cut not a cut?

Not when it is an adit, which are at an angle. The only canals approaching being an adit are the inclines at Montech and Beziers, with the scheme to have an inclined canal tunnel under the Alps, where the boats were pushed up and down on a wedge of water, probably falling into this category.