Skip to comments.Finding, filling old mines a major part of Southern Beltway construction
Posted on 11/28/2017 8:03:42 AM PST by Tolerance Sucks Rocks
Almost no matter what you build in Western Pennsylvania, you have to consider the possibility that in previous generations the site had been mined for coal.
Thats especially true for the next leg of the Southern Expressway, a 13-mile, $700 million section being built along part of the Pittsburgh coal seam between Route 22 and Interstate 79 in western Allegheny and northern Washington counties. In the area around McDonald alone, where the highway will pass over Route 980 just outside the borough, at least 10 mines operated within two square miles between the mid-1860s and mid-1930s.
Particularly in Western Pennsylvania, its important for highway designers to know whats hidden hundreds of feet below the surface so they can determine whether the ground is stable before they build bridge piers and other structures on top of them that could weigh millions of pounds.
Whether the mine walls have remained intact or have collapsed, land that has a history of mining often isnt a solid surface on which to build. Regardless of their condition, old mines leave openings, known as voids, that could cause shifting under the heavy weight of construction.
To fill those openings, crews can pour as much as thousands of cubic yards of grout into the ground to create a buildable surface.
We dont know the extent of mining, said Steve Hrvoich, construction engineering manager for the Pennsylvania Turnpike who is overseeing the toll road extension. We have no idea how much of that is void underneath there.
Identifying and filling voids is one of the most time-consuming processes of road construction. For the bridge over Route 980, crews began drilling holes last spring and didnt finish until the end of October.
(Excerpt) Read more at post-gazette.com ...
How to build a highway: Finding, filling old mines a major part of Southern Beltway construction
Sounds a lot like trying to fill the coffers in Washington DC. You pour thousands and thousands and more thousands of cubic yards of dollars into the void and it never, ever gets filled up.
And it might collapse under load, at any time.
And it won’t be just a bridge, BUT THE ENTIRE ECONOMY!!!
>>And it wont be just a bridge, BUT THE ENTIRE ECONOMY!!!
[Massive Sinkhole Documentary - World’s Most Terrifying Sinkhole - Documentary HD]
Seems like dynamite would work?
Few places in this part of the world are NOT undermined.