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Tunneling With Multiple Water Jets

08/26/2019 8:00 AM

firstly one I don't think tunneling machines work very well considering the breakdowns and slow cut speed aside there own mass is a problem and the varying density of what it's cutting seems to be the major issues surely 100 water jets working on multiple axises and cut angles would yield a faster cut speed and lower the required weight of the machine

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#1

Re: Tunneling With Multiple Water Jets

08/26/2019 8:22 AM

I'm not a mining engineer in any aspect but dealing with the water and slurry run off from 100 high pressure water jets sounds like a bad idea when under ground. I think one of the reasons a tunneling machine moves so slowly is the problem of supporting the earth above the tunnel. Those tunnel walls must be ready to support before the machine moves.

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#2
In reply to #1

Re: Tunneling With Multiple Water Jets

08/26/2019 8:36 AM

water jets use a lot more air then they do water a little triangle of dirt would be way easier to move as the size would very little to not at all as for the support I was thinking collapsable piping

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#3
In reply to #2

Re: Tunneling With Multiple Water Jets

08/26/2019 9:48 AM

A tunneling machine bores through materials of different hardness. This might be why a water jet will be used to mine at one place but not the varied substrates needed to make a tunnel.

Then again I am making guesses outside of my field. For all, I know there may be water jet based tunneling machines out there but neither you nor I know it.

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#6
In reply to #2

Re: Tunneling With Multiple Water Jets

08/26/2019 10:41 PM

Water jets also use an abrasive, which must be harder than the material being cut. The amount of abrasive required for tunneling through bedrock would hardly be trivial...

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#16
In reply to #2

Re: Tunneling With Multiple Water Jets

08/28/2019 8:54 AM

Eh? The amount of spoil to be removed from a tunnel will be a constant regardless of the method of cutting!
Unless of course you vaporise the material with a sci-fi laser tunnelling device...
Del

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#4

Re: Tunneling With Multiple Water Jets

08/26/2019 12:53 PM

Relatively large-diameter horizontal boring machines, with out much water-jetting, seem to have worked well enough during the construction of the 31 mile long ''Chunnel'', from 1988 to 1994, at some 790 feet below sea level of the English Channel, and some 250 feet below the sea bottom thereof...

Which averages out to be about .0535 feet-per-minute, through bedrock...

If they had relied more heavily on a water-jetting technique, they would have supplied an additional source of vibration, and an additional water supply to carry away losened rock, thereby promoting additional risk of rock-slides and cave-ins.

Any mining speed that risks more cave-ins is too much speed...

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#7
In reply to #4

Re: Tunneling With Multiple Water Jets

08/27/2019 12:53 AM

you cannot tell me that cutting a few millimeters of rock precisely will increase the risk of cave-ins more than ripping it apart with what amounts to a giant drill

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#9
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Re: Tunneling With Multiple Water Jets

08/27/2019 3:57 AM

Yes the use of TBM’s , road headers or drilling from a jumbo do produce fractures in rock , the deeper you go underground the higher the pressures are that will be encountered , rock will often “stress relieve” when its cut so some fracturing is natural.

waterjet cutting won’t require 100 nozzles , 6 to 8 nozzles controlled by CNC sequenced cutting patterns could give the best efficiency and in sandstone we calculate that cutting depths of 300 mm are achievable , this also suits the maximum size limit for removal by conveyor.

ps. We have cut through 800 mm thick reinforced concrete columns using waterjet with abrasive media , and 2000 mm cutting depth should be achievable with a low cutting travel speed.

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#5

Re: Tunneling With Multiple Water Jets

08/26/2019 5:29 PM

The completion of the new downtown tunnel in Seattle was a chore. Bertha was a beast...the largest of her kind at the time.

Adding any amount of water there was not possible. There was enough of a problem there already.

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#8

Re: Tunneling With Multiple Water Jets

08/27/2019 3:39 AM

Well done you.

i have that idea and 2 other variations of it in my design books from 2010 when working on a tunnel project in Australia.

i discussed it with the client but they were already committed to the TBM they had on order but we did use waterjet for cutting concrete columns on the same project where hydraulic hammers couldn’t be used.

It will be feasible in some environments where the tunnel floor allows rubber air filled bellows as a movable dam to allow suction pickups for water recycling.

Less than 30,000 PSI is required with no abrasive media .

It will be done eventually.

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#10

Re: Tunneling With Multiple Water Jets

08/27/2019 6:03 AM

No matter how you cut the material there is still the volume and tonnage of the material to be moved out of the way as the boring machine progresses. There would need to be many more jets as the typical boring machine has a large number cutting edges to remove the material. Imagine how many water jets would be needed to cut a 20meter diameter hole?

Add water and you are dealing with a slurry which has an increased volume because of the increased moisture content and if you have ever tried to move slurry then you will know it doesn't want to stay on conveyor belts unless they are almost horizontal or you dewater it first and this requires vibrating screens, cyclones and even centrifuges so there goes any weight saving. Slurry can be pumped but a certain velocity has to be maintained else it settles out and a pipe full of solidified slurry is not a nice thing to clean out. How do you recycle the water for reuse or will this valuable commodity just be discarded with the spoil?

Best stick with what works after all these boring, tunneling or mining machines have been refined over years of use until they are currently the best solution for cutting through multiple layers of various hardness of rock.

I watched NBN installers using water jets but only to clean out conduits underground and then the vacuum truck was needed to remove the spoil. What did they use to make new passages for conduits, directional boring machines of course.

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#11
In reply to #10

Re: Tunneling With Multiple Water Jets

08/27/2019 7:59 AM

Dewatering equipment would weigh no more than a cutting head which is now not required.

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#12

Re: Tunneling With Multiple Water Jets

08/28/2019 7:39 AM

I'm thinking optimizes the cutting format to create stable structures you guys are thinking of it as a circle and I'm thinking shape that will be optimal for the support you could make mini structures it would lead to decreased load

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#13

Re: Tunneling With Multiple Water Jets

08/28/2019 7:57 AM

How do you get the cut material to drop? All of the water jet cutters I've seen work on a clamped piece of material. The cutter cuts in two dimensions but nothing holds the material in the third dimension. Bedrock is firmly held in all three dimensions. Will the water jets not be orthogonal?

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#14
In reply to #13

Re: Tunneling With Multiple Water Jets

08/28/2019 8:37 AM

first, a small hole is made to relieve the pressure then the jets themselves would intersect at a point allowing a cut point

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#15
In reply to #14

Re: Tunneling With Multiple Water Jets

08/28/2019 8:44 AM

think of it like cutting small cones that amount to shapes and the negative pressure should remove it

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#17
In reply to #15

Re: Tunneling With Multiple Water Jets

08/28/2019 9:41 AM

Half the cuts could be parallel to the tunnel floor (perpendicular to the tunnel face)

the other Half would be angled to intersect them at 45 - 60 degrees so the cut segments would drop out to the floor and be swept up by the same collection arms as used on road headers and long wall coal headers.

the volume of cut material would be less than what’s produced by a header or TBM , as density is in your favour.

the people shooting down the idea are doing so because they know how good the concept is.

As I mentioned above , I put work in to this very idea back in 2010 but I also have a better one which wont get posted here :D

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#18
In reply to #17

Re: Tunneling With Multiple Water Jets

08/28/2019 10:06 AM

I just want to be clear here. I'm not trying to shoot down this idea. I'm helping to make sure all complications are mitigated.

At the same time, I still suspect that the cutting process is not what slows tunneling down. These monster machines are concurrently performing multiple tasks. It can only move faster if the slowest concurrent process is sped up. There may still be additional advantages to a waterjet instead of a cutting wheel.

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#19
In reply to #17

Re: Tunneling With Multiple Water Jets

08/28/2019 10:10 AM

I don't think the cut speed would be slower based on energy input if you input the same energy that you would input into a tunneling machine

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#20
In reply to #19

Re: Tunneling With Multiple Water Jets

08/28/2019 10:21 AM

these machines are automated or control by people remotely so as far as I am concerned energy input and work time are bigger factors for me

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#21
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Re: Tunneling With Multiple Water Jets

08/28/2019 11:11 AM

Saving power is a good attribute for a change in design. Reducing downtime to make a net increase in tunneling speed is also a good attribute. Both of these attributes can rarely be achieved without sacrificing something else, particularly with a complicated machine. Increasing the cutting speed without addressing the time of any other concurrent task (i.e. removing spoil, shoring walls) might not make for an improvement.

I wish alex12 and Nothing is Impossible good luck in improving these impressive machines.

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#22

Re: Tunneling With Multiple Water Jets

08/28/2019 3:25 PM

How about a subterranean LASER to just vaporize the offending rocks, of course those vapors might be a little problematic (wink,wink).

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#23

Re: Tunneling With Multiple Water Jets

08/30/2019 6:51 AM

A large boring machine produces 2600TPH of spoil which being mostly dry can be conveyored away to be collected and dumped. Can the envisioned water jet machine cut at the rate of 2600 TPH and provide suitably dry material to transport away on a conveyor? I know from working in a washplant that to dewater even 1000TPH of wet spoil takes a lot of energy and equipment to provide semi dry spoil.

So how big would the pumps need to be to provide water at 30000PSI at the volume needed? Having worked on oil drilling rigs doing fracking the size of the pumps needed to supply the pressure through 4 inch drill steel was in the order of 3000HP. One even used a turbo jet engine to drive the pump delivering liquid nitrogen and that was many thousand more horsepower and the scream was horrendous.

Seems like an idea which would need more development to prove the concept at full size.

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#24

Re: Tunneling With Multiple Water Jets

09/01/2019 6:32 PM

The range of the NLB 605 Series has been expanded to include eight operating pressures from 4,000 psi to 40,000 psi (275 bar to 2,800 bar), with engines of up to 600 hp (447 kW). Diesel and electric models are available. Offering flows as low as 20 gallons per minute (83 liters per minute), the units can be converted from one pressure to another in about 20 minutes and are easy to maintain.

How will you put 100 of these pumps inside your tunnel?

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#25
In reply to #24

Re: Tunneling With Multiple Water Jets

09/01/2019 9:36 PM

6 to 8 jets are required IMO

look at your photo . At least half the space is occupied by a 6 cylinder Diesel engine and its fuel tank.

Remove that and replace with an electric driver motor , now stack 6 of them in one segment of TBM and they only take up the TBM diameter by a length of 3 metres

that unit is also big enough to comfortably run 2 - 3 cutting jets.

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#26
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Re: Tunneling With Multiple Water Jets

09/03/2019 3:15 PM

To ''Stef'' and ''Nothing is Impossible'', I particularly appreciate a pair of engineers with actual tunneling-engineering-related experience taking time to ''weigh-in'' on this topic. Thank you and Thank you.

And a GA to you each.

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#27
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Re: Tunneling With Multiple Water Jets

09/03/2019 5:09 PM

No problem .

It will be patented and manufactured within 3 months by an Israeli engineer operating out of an address in Moldavia who sells it to an equities trader’s cousin whose mistress is on the board of a fund manager in New York which will buy shares in the company , strip out its assets then run it into the ground.

or something like that.

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#28
In reply to #27

Re: Tunneling With Multiple Water Jets

09/05/2019 12:17 PM

Add some car chases, explosions, luxurious settings, etc., and it sounds like a good plot for a historical documentary action movie...

(...as long as all the names are changed to ''protect the innocent'', as Dragnets' Sgt. Joe Friday used to say...)

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