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Discussion Starter · #1 · (Edited)
Submerged (floating) tunnel concept (China/Korea/Japan/Russia)

Some time ago a project was announced to build a tunnel under the Yellow sea to connect Dalian with Penglai. The Yellow Sea has a maximum depth of 152 m and is 44 m deep on average. Even a tunnel connecting China with S Korea was proposed. See: http://pulsenews.co.kr/view.php?year=2015&no=1021787 (Although a connection with N Korea would be a bit shorter, but under the current political circumstances impossible, unless of course the peacefull North-South Korean relations really make it possible, we have to see and watch and hpe for the best)

Another interesting aspect of Yellow sea is that it has significant tide difference (4-8m), making it potential location for tidal power station.

This lead me to thinking about a radically new design for a tunnel, one that does not need boring but is submerged (at least 30m under sea surface at low tide to allow maximum ship depth based on ChinaMax - 24 m) and is combined with a tidal power station.

The connection Penglai - Dalian is 105 km (straight line), but several island exists there at about 65 km for the farthest island from Penglai. So, in principle you could connect all those island by a dam (which narrows the distance to 40 km, and instead of digging a tunnel under the remaining strait, one could build a submerged tunnel - either as a buoyant tunnel attached with cables to the sea floor, or as a submerged tunnel attached to an underwater bridge (max height of pilars would be some 120-130 m, seems doable).

At the bottom of the sea (and/or as part of a submerged bridge) tidal power generators can be attached to generate electricity.

The tunnel design would be a tubes-in-a-tube kind of design. For example 2 inner tubes for trains (with linked escape/service tunnel) and 2 inner tubes for cars (with linked escape/service tunnel) and some smaller tubes for e.g. gas/oil/electricy/data links. All these inner tunnels combined fit within a larger outer tube (hul material probably steel?), and the space between can be filled with buoyant (water resisting) material (in case of a floating design), for example expanded polystyrene (EPS) which is lightweight, cheap and water resistant. Inner tunnels can be made from steel or concrete. The whole tunnel must have a tolerance of at least 1% for movement (due to ocean movement and/or as part of the trajectory lay-out), that is for every 100m the tunnel must at least accomodate 1m deviation from a straight line in any direction.

Aspects of this design are:
1. The submerged tunnel should be able to withstand the forces due to earthquake/tsunami (as well as the normal forces due to tidal sea flow, but that is presumably a lot less then the forces caused by earthquake or tsunami) as well as the forces in case of collision with a vessel (submarine or a sinking ship).
2. The tunnel could be built in compartments that can be closed down water tight in case of emergency (tunnel collapse/break or fire), with added escape shafts for each compartment to the sea surface (evacuation shaft to be attached to the compartments after the tunnel is finished for easier construction). Which begs the question: what if a train or car blocks compartment seperation so that closing it is not possible and how to avoid collision with the seperation that closes the compartment, if traffic still moving in the compartment to be closed down...
3. Tunnel construction could be completely on land, building section by section (sections can be prefabricated) and assembled into a compartment of some specified length (approx. 1 - 5 km length) and then pushing (and/or dragging) the new compartment into sea towards the other end/shore. Front part is water sealed (which get removed once the tunnel reaches the other end).
4. At build site and on other land side first a guiding tunnel is constructed (connecting land level to the appropriate underwater level with at most 1% gradient). On both land ends a trench is digged and a guiding tunnel is built in which the tunnel can be shoved (using gliders or sets of wheels to decrease resistance).
5. Building is done at one end only, as connecting the two halves midway and underwater would seem difficult (but perhaps not impossible, and it would halve the built time).
6. During the built the floating tunnel is kept at the appropriate water depth (some 30 m below low tide sea level) by anchoring it with temporary anchors to the sea shore - these temporary anchors have rollers at the tube that allow the tube/tunnel to be shoved further towards the other end while keeping their position and when tunnel build is finished, can be permanently attached to the tunnel/tube.
7. The layout of a tunnel consists of:
a) sections that make up a compartment. The number of sections that make up a compartment depend on section length and compartment length. E.g. section lengt: 100 m, comparment length 5k, around 50 sections make up a compartment.
b) compartment connectors that connect two compartments and has at both side water tight seals that can be closed in emergency for every inner tunnel. Both parts can be closed in order that a damaged compartment can be taken out as a whole for repair or replacement without causing the rest of the tunnel to flood. A spare compartment is standbye so that replacement can be done quickly.
c) each compartment has in the middle a connector part to which a vertical escape shaft can be connected, which connects the tunnel to some sea level platform (due to tide difference some part of the escape shaft will extend beyond sea level - the platform floats around the escape shaft at just above sea level - just high enough that normal occuring ocean waves are below it).
Both for the compartment connector (or inner and outer tubes) and the escape shaft connector, some kind of underwater docking mechanism must be developed.
d) Escape shaft will also accomodate ventilation shaft.
e) Inner tubes accomodate the needed traffic links, one for each direction and one escape & service tunnel. Ignoring other service links (like eletricity cables, oil/gas pipelines, data cables) thus a layout can be made of consisting of 3 inner tubes (either car or train) or 6 inner tunnels/tubes (for both car and train).
8. Dimensions of tunnel/tube. The outer tube has dimensions (height/width) that are like 2-3 times the size of each inner tube/tunnel (some 8m diameter), depending on inner tunnel layout (car lanes only? train lanes only? Both cars and trains?) and buoyance requirements. Assuming a perfect round design is best, height and width dimensions are the same.
9. Buoyance of a compartment will be significantly high so that even a maximally densily packed tunnel with vehicles and trains and fully flooded will still float.
10. It is of course possible that a floating tunnel design and non-floating design (resting on pillars or in trench or as part of a dam) can be combined, and only use the floating design for portions of the route for which pillars would extend too far. Given an average depth of 44 m for the Yellow sea, some larger portion should be able to be built inside a dam, some portion on pilars and submerged tunnel design. Assuming a total height of tunnel assembly of 10m (or 20-25 m for both car and train tunnels stacked on top of each other) and depth below low tide seawater surface of 30 m, it would mean an important part would be laid in a trench, another portion on small-medium size pillars, and only small portion would need some buoyant part. At the parts that have a fixed connection to the ocean floor, tidal stream power generating turbines can be attached.
11. Environemental studies and analysis should be done on changing tidal motions for each design proposal to avoid detrimental effects on the environment and for calculating the strength of tidal motions (both generally and under specific conditions of earth quakes and tsunami) for both the necessary strength of the construction and for the anticipated tidal power production.

Other locations for a similar type connection are:
a. China (Penglai) - China (Changju) - Bohai sea. Length: 98 km (shore to shore).
Current proposal is an under sea floor tunnel that need to be digged, which makes it expensive and the length is unprecedented (at least 2 times longer then british-french channel tunnel)

b. China (Cangdao) - N Korea (Changyon/DPRK). Yellow sea. Length: 192 km (shore to shore)
Connecting both Pyonyang and Seoul to China through Yellow Sea. (shorter route as China - S Korea, and might become possible as N Korea - S Korea relations finally seem to thaw and improve in the direction of permanent peace. Definately an option in the not so far future, more cost effective and benefit for both Koreas!
Current proposal is to connect it to Incheon (S Korea) as an undersea floor tunnel design. That tunnel would be over 322 km long (shore to shore), 6 times longer as the British-French channel tunnel! Due to the huge costs, it is not yet considered an option.

c. S Korea (Geoje) - Japan (Karatsu). Sea of Japan. Length: 172 km (shore to shore).
Using 2 intermediate islands, the distance can be broken down in shorter stretches.

d. Russia mainland to Sakhalin (Lazarev to Pogibi). Length: 7,34 km
Could be built best as partial tidal barage/dam and other part as submerged tunnel or bridge.

e. Russia Sakhalin southernmost point - Japan Hokaido northernmost point. Length: 64 km

f. Russia / Kamtsjaska. 3 possible locations at Penzhin bay Kamtsjaska, most northern part of sea of Ochotsk (the "armpit" of Kamtsjaska). Lenghts: 182 km (widest). 71 km. (middle/south). 27,5 km (shortest/north). See: Penzhin Tidal Power Plant Project
Here the world largest tidal difference is measured and thus an ideal location for a tidal power station. Building a tidal power station here was already studied in soviet era, but as there is nothing there that could need such a large electricity power station, the plan was mothballed. A tidal power station could however be usefull for powering the future Siberia-Alaska railway passing the Beringstrait. An extention to the railway (current furthest most point is Nizhny-Bestiak near Jakoetsl) to Magadan is foresee to be built between 2020-2030. The last part to the Beringstrait somewhere near 2050.
Meanwhile the electric power could be delivered to Japan and/or Korea...

Note: A submerged tunnel design is a radical new type of construction, not yet built anywhere. However Norway has made a proposal/design for such a submerged tunnel to connect the shores of fjords. See: Norway Floating Tunnel concept
NB. What seems strange in the design - as pictured - is that the buoyant part of the tunnel is placed at the sea surface, which would be an engineering challenge as the water level is dependent on tides yet the tunnel itself should be at fixed height above the sea floor as it has a fixed land connection, so they have to lower/raise the connection between the tunnel and floaters to compensate for the tides. A buoyant tunnel design would eliminate that problem since then the tunnel would support itself, just that it needs to be kept in place using cables attached to anchors at the seafloor. Perhaps the Norwegian designed tunnels are anchored to the sea floor too?

Other floating tunnel location possibilities in Asia include:
1. Malaysia/SIngapore-Indonesia/Sumatra:
a. Pulau Karimunsbesar (indonesia/Sumatra) - Kukup (Malaysia). Strait of Malacca. Length: 19 km. Other shorter parts are necessary to connect to Sumatra mainland.
b. Singapore-Batam (Indonesia). Strait of Singapore. Length: 7 km. Many addiational parts (of shorter or similar length) are necessary to connect to Sumatra mainland.
2. Indonesia Sumatra-Java. Java sea. Length: 25 km. Can be split in two tunnels when connection made via Sangjang.
3. Indonesia Java-Bali. Bali sea. Length: 3,87 km. Bridge would most likely be best option. Java-Madura bridge already built connecting Surabaja with Madura.
4. Philipines. Many possible locations.
5. India-Sri Lanka. Gulf of mannar. Length: 30 km. Since this is a former landbridge a normal bridge design could fit here.
6. China mainland - Hainan. Length: 20,5 km
7. Iran Suza - Oman Khasab. Strait of Hormuz. Length: 58,6 km.
8. Yemen Perim island - Djibouti Moulhoulé. Strait of Bab al-Mandab. Length: 21,91 km. Plus additional shorter stretch (bridge/tunnel) from Perim island to mainland Yemen.
Question:
The tough question is though - can anything like this be built, is such a submerged tunnel able to withstand the forces of the ocean, even earthquakes and tsunami? Would it be safer then an underground (under seafloor) tunnel or normal bridge? Would it be cheaper to built then an underground (under seafloor) tunnel (this design saves the cost of tunnelboring, but adds cost for an outer tube and anchoring/underwater bridge,and the design concept is novel wich adds to development costs).
Likely though it would be much faster to built as the primary construction work could be done on land (compartments added and shoved into sea, built from sections already prefabricated, including road and railway tracks, with only minor post assembling work).
 

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Discussion Starter · #3 ·
Norway is long planning one in Stavanger or Bergen too....it ain't all Asian
That is what is stated in my post. None are proposed in Asia at all, it has in fact nothing to do with Asia at all. Apart from the fact that Asia has a lot of straits and islands that are not connected, and could use a cheap and safe technology for connecting such straits.

I just wanted to discuss the technical opportunity for such an alternative and how it would compare in terms of safety, building costs and time to built.
 
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