Help me solve an Indy puzzle!

[Bruce Bergman]

Hey, work construction long enough and you spot the "How the heck did they do THAT?!?" stuff - then you find out how they did it. Comes in handy later, when you can modify the idea and recycle it. (Usually scaled way down, or for a totally different field but the same problem.)

Sheet piling is great stuff - watched them rebuild a gas station near me, they needed a new concrete "bathtub" for the tanks to sit in, in the only sandy soil in the area. (It was the creek-bed a few millenia ago.)

They drove in a square box of sheet piling, excavated the middle, built a rebar box, poured the slab, formed and poured the walls, then pulled out the piling sheets. All done, real fast, real clean and neat.

Next time they need to change a tank it will be easy, remove the driveway slab and they are sitting in the concrete bathtub filled with pea gravel. And if it managed to leak /and/ get past the secondary containment tank, the gasoline should stay in the bathtub.

Originally Posted by Mojave

With the old way, the trench would be dug down to the bottom, correct? Considering that JC berm looks to be about 15' tall, you're talking about a big wall of dirt! How did they keep that from crumbling? Is it a matter of wetting and compacting before digging the trench? I can understand "nobody went down in there"!

From the Indy construction photos, it looks like they had left the timber planks in place rather than removed them. Is that normal? You seem to suggest normally they would remove them after building the permanent wall.

There's a dozen ways to do it... They can easily leave the planks there forever, eventually the dirt will subside a bit as they rot away over the next ~50 - ~100 years, but would be like natural settling. Or they can fish them out when done, as long as they don't have to go down there.

The 'trench and drop in on the backside' method has a practical limit of how far down the can reach with an excavator bucket. Past that, there are other solutions...

I've also seen it done where they drive the I beams, then they cut railroad tie sized timbers and slide them between the beams, let the I-beam flanges hold them. Excavate the backside and in between the I-beams, and let the timbers slide down to fill the gap as they dig down - add more timbers at the top as needed.

(They are using this one to widen I-405 through Culver City. And there are apartment buildings 10' back from the new wall, and a good 30' above the freeway. Don't make any big mistakes, or their living room will be in the slow lane...)

And they can take out every third or fourth I-beam and two sections of timbers, then form and pour a slab of concrete wall. Then take out another third of the temporary wall and form/pour that... As long as it's well compacted soil and they don't remove too much support at once.

--<< Bruce >>--