Gas Pains

Tom grew up in Milwaukee, bartended in Wauwatosa in the '70s and moved here in 1984.

Commentary, observations and musings about the outdoors, life in general and maybe Tosa politics and personalities will be the order of the day. He savors a lively debate as much as terrific cooking.

Tunneling Under Tosa

Technology, Impressive Construction Projects, Just For Fun

Here I am - underground - west of Highway 45 and somewhere below Wisconsin Lutheran College's practice field.  This tunnel is as big as a subway tube.  It is soaking wet with sucking goo everywhere and noisy.  It stinks a bit of diesel too.  But I'm used to that.

What a way to spend a sunny Monday afternoon.  I love being underground.

And I had a blast.

There was blasting?

No.  There was boring.  But it was not boring.

I got wet, covered in muck, got to clamber over all sorts of dangerous machinery, squirted with grout, and was reaffirmed in my belief that you should never venture forth on a slippery adventure with a digital camera worth more the $100.

When I returned home I had to disrobe on the porch.  And I learned that cheap Kodak cameras are resistant to flying grout.

This all began when I hitched a ride with the man operating a 35 ton locomotive hauling a grout car, empty muck boxes and enough precast tunnel segments to complete one ring of tunnel segment.

I wrote about the MMSD's tunneling operation last December so it was about time to check-out the progress of the operation.

But before I could even set foot into the tunnel I was made to sit through a grueling safety lecture, lace-up my steel toed boots, put on a hard hat, safety goggles, hi-vis vest and ear plugs.  There was also a giant waiver the lawyers made me sign.

Mining operations are difficult and dangerous work.  Safety is right up there next to Godliness.  I learned that when underground - communication is largely by hand signals, different colored lights or very loud horns.  It is just about impossible to carry on a conversation short of shouting into someone else's ear.

I learned even more about the the lovely Luminita on this visit.  And got to see it in action - up close and personal.

Luminita is the quirky name given to the machine that is mining the tunnel.  In the vernacular of mining engineers this is what is known as an Earth Pressure Balance Machine (EPBM).  Or Tunnel Boring Machine - TBM - for short.  It is manufactured in Canada by Lovat.  It weighs-in at a cool 700,000 pounds and is driven by hydraulic pumps powered by 13,200 volts of juice.

Here is the man driving it.  He's got more levers, buttons and switches than the Wizard of Oz had behind the curtain.  If you look very carefully you can see part of the laser guidance system located at 11 o'clock above his head.

The operator signaled to me to not block the laser with my big noggin.  I'm thinking - Oh man, Tom, if you block the secret laser guidance thing the machine might go off-course.

You know me - I don't want any trouble - so I kept my head down.

It was shortly after this that the power went out and the entire tunnel was plunged into darkness.  The machinery groaned to a halt.  Everything stopped.  Headlamps were switched-on and everyone was giving me the hairy eyeball.

Hey!  Don't look at me fellas.  I didn't touch a thing.  Honest.

Power was restored. 

The tunnel boring machine uses sixteen hydraulic jacks (12" bore by 88" stroke) located in the rear to push against the last precast tunnel segment.  Four 400 HP motors drive the cutting head at the front of the machine which chews-up the earth and boulders in its path.  As it advances the spoils are delivered by auger out the back end for removal.  Water is added for lubrication so the stuff exiting the auger looked remarkably like soft-serve ice cream - in an unappetizing hue of gray.

When sufficient forward progress has been made then the six tunnel segment pieces that arrived on the train are erected at the back-end of the machine.  This section is called the Tail Can and it provides protection for the miners.

As the assembled section of tunnel leaves the tail can - grout is forced under pressure into the exterior voids to seal the tunnel segments and provide additional support. 

Visualize a large horizontal well casing. 

The hydraulic jacks are repositioned against the completed segment - each one capable of 250 metric tons of force - and the process is repeated.  On Monday afternoon - 10 segments had already been assembled for a total of 471 to-date.

Without complications that's about the average rate of daily advance. 

As of five days ago the project was two-thirds complete.

Hey Tom - there must've been an army of workers down there in the hole wasn't there? 

Actually not so many. 

I was thinking about how this might have been accomplished if it was taking place more than a century ago.  I kept conjuring-up an image of a vast workforce of immigrant laborers wielding picks and shovels.  Hauling stuff out in horse-drawn carts.  Rickety timbers supporting the laying of bricks.  Poor lighting, the constant threat of cave-in and collapse.  String instead of lasers to point the correct direction.

This is a highly mechanized operation.  Including the electricians there are twenty individuals working a single shift per day.  Funny - they all seemed to be rather close in age to me.  No kids on the crew.

For a small group on a big project they get a lot accomplished.  35 to 40 truck loads of spoils are removed during an average workday.

By the time the job is complete the train will have made more than 680 round trips.

If you are traveling down Highway 100 you can see the construction work proceeding on the west end of the tunnel just east of the post office. 

The machine will exit here.  I am told it probably won't be off course by more than a half-inch.  Give or take.

I sure hope someone over at the MMSD shoots some video of the exit.

Because if they do - I'll post it.

The following animation is for a much larger hard rock mining machine - but the process is basically the same.


This site uses Facebook comments to make it easier for you to contribute. If you see a comment you would like to flag for spam or abuse, click the "x" in the upper right of it. By posting, you agree to our Terms of Use.

Page Tools