Driving Big I beams into the ground....

So it has been in the news that much of the Ford Campus here in Dearborn is getting a major facelift.

The first job they are doing is putting in a new parking structure.

And the first of that job is driving what appears to be 100 ft I beams into the ground.

So for the construction and civil engineers out there- what is the mechanism that they are relying on to rest the building on it? Is it that the beam is sitting on bedrock or that the friction in the soil is doing the work?

It's interesting to see them run into stuff as it's driven in- the sound of the pile driving changes a lot when it reaches a solid object- the beam rings even when it's mostly in the ground. Sometimes they pause and try driving it farther, but sometimes it looks like they stop- the height above the ground is different on the beams they've driven so far.

Should be an fascinating few years while all this goes on.

around here, any and all big buildings are supported by beams driven into the ground. Most of the houses near the ocean are too. It's a system that works well and has worked well for decades

I know that part- but are they resting on bedrock or just the friction?

I know this doesn't help answer your question, but you brought up some memories for me. About 20 years ago I lived downtown and was the only person for quite a ways to live there. They were redoing the area completely and couldn't drive piles during the day for fear of interrupting all the business going on. Instead they fired that thing up at 6pm and worked all..night..long. I was literally just a few hundred feet from that thing, in a 100 year old building, trying to sleep. I'll never forget what that sounds like.

It could be both, but probably friction.

I would guess they have a target depth they need to drive them to, depending on the amount of support needed and soil conditions, unless they hit an obstruction. Then they will just cut off the top of pile later. for now wood planks will hold back the adjacent dirt but eventually the final concrete foundation walls will be poured in front of and around those beams.

As part of our surveying services we provide pile monitoring for many projects in the DC metro area. Basically we stick reflective targets on the piles, locate them at the beginning of the project, and go back on a weekly basis (or more) and locate the same targets and monitor them for movement. If we see increasing movement trends it can provide advance notice that there is about to be a bigger problem, so to speak.

Friction. The content of the soil will determine the linear length needed to reach the targeted suspension.

Friction, they have to withstand a certain pressure on them without moving downward anymore.

They are doing earth anchors near me, thats interesting, drill a 12" ish hole with a special drill that has a hopper on top and is hollow, they fill the hopper with gravel that backfills as they pull the bit back out. It also compacts as it places. Nuts.

Down here in the land of mud, they are looking for the Cooper Marl layer that is about 300' down. There is nothing of substance above it. Smaller structures float on the surface, but the big one have 100s of piling driven under them.

I never see them use i-beam though. It's always 12X12 piling or steel caissons that are then filled with rebar and concrete. That might be due to the salt we get into some of the deeper aquifers.

In reply to Appleseed, java230:

Thanks.

If the written numbers on the beams mean anything, they are starting at #60 and working down. This for a multi story parking structure.

numbers would just be pile numbers. So when the surveyor tells them piles 16-18 are caving in they know where to bring in some additional support.

They built a subway barn next to the depot I drove out of in Flushing. Everything there is on top of landfill. Sometimes the pile driver would hit one and it would pretty much disappear into the ground.

Pilings can be friction or end bearing.

I had a building project near HHI, SC with driven wood piles. During driving operations, they found out the property contained a LOT of buried automobiles.

I was driving pilings in Bristol TN. once. I was about 60' deep with the first piling and broke through the top of a cave, the ten feet I had sticking out of the ground disappeared in an instant. Craziest thing I've seen. That area was a nightmare though, we would average 120' on a project and a half mile away we would average 10'. Made predicting how much material to bring with us a challenge.

In reply to Nick (picaso) Comstock:

They did some test drilling here a few months ago- so I hope they have a good idea. The other interesting thing- this is on a parking lot- and they just drive them through the surface. The base of this structure will be a former parking lot.

Similar situation, MUCH smaller scale: a guy I worked with wanted to extend his house (that was formerly his cottage, prior to Marital Events.) This was in the Kawartha Lakes. Local code said footings had to be X feet deep if possible. He dug down as far as he could, which wasn't that far, and called the building inspector. The inspector came by, took out the Official Hammer, whacked the bottom of the hole a couple of times, said, "Yup, that's Canada," and signed the form.

Depends on the site, but either end bearing on rock or other suitably dense layer, friction along the length of the pile, or a combination of the two. HP piles (shaped like an "I" or a typical steel beam) don't displace a lot of soil so they are commonly used in clay or silty soils where friction between the soil and the surface of the pile is high. They have a large surface area due to the shape so the friction is maximized. They are also commonly used where there is limited friction between the soil and the pile but rock (or other suitable material) is relatively close to the surface so you develop all of the resistance in the end of the pile bearing directly on rock.

In sandy soils where rock is very deep, solid square or octagonal piles are commonly used because they displace a large volume of soil when they are driven. This displacement causes the soil to become more dense and increases both the friction along the side of the pile and the bearing capacity of the soil beneath the pile.

Another phenomena of driven piles is "pile setup" or "pile freeze" where the piles develop additional resistance over 24-96 hours after they have been driven. In the case that Toyman was talking about where they drive to the Marl, the overlying soil is very soft and provides very little resistance to driving. When they hit the stiffer Marl layer the driving becomes more difficult but still doesn't provide sufficient capacity. But, the Marl is a strange material that doesn't instantaneously provide full resistance. Stopping and waiting a day or three allows the Marl to establish "setup" on the pile and when you come back and try to drive the pile again, it takes much more effort so in effect it now has greater resistance. There is an identified mechanism that is fairly well understood as to how/why this occurs, but it is somewhat complex to try and describe here.

Stealthtercel wrote: Similar situation, MUCH smaller scale: a guy I worked with wanted to extend his house (that was formerly his cottage, prior to Marital Events.) This was in the Kawartha Lakes. Local code said footings had to be X feet deep if possible. He dug down as far as he could, which wasn't that far, and called the building inspector. The inspector came by, took out the Official Hammer, whacked the bottom of the hole a couple of times, said, "Yup, that's Canada," and signed the form.

I figured that Detroit probably had the big ol' Canadian Shield not too far down to build on. But looking at maps, it doesn't go there.

My old house in Ottawa was built on the Shield, to the point where part of the basement was only about 2' deep and had a sloping rock floor. Never had to worry about that puppy settling.

In reply to Keith Tanner:

There were places like that in East TN. as well. Unfortunately the "builders" would stop short of the solid rock, sometimes by a foot or so, and sometimes by a couple inches. So what happens when the water wants to run along the surface of that rock and washes that layer of soil form in between the footing and the rock? Big giant cracks in the foundation and walls is what happens. Ah, East TN, the land of zero codes and zero code enforcement and my uncle built a barn once, I'll get him to build my house. "Yeah, sure we can do a two story. No, no, no 2X6 joists on 24" centers will be more than enough"

I do not miss it, not at all.

Height wise, we are only a few feet above the Detroit River- as the local river flows into that- so we are roughly not much higher than the average of Lake Huron and Lake Erie.

The piles are longer than our distance above the water line, I would say.

But this area is mostly deposit areas of the glaciers, and not really the scraping area. Gravel, sand, clay, sure- but not solid rock anywhere near by (as far as I know).

So the friction explanation now makes a lot of sense- especially when put into context of other pilings and how they work.

Geology wise Detroit is on the edge of an ancient ocean basin. That's why you get the massive evaporative salt deposits that underlie the Detroit area.

Alfadriver - This is completely unrelated. Have you ever eaten at Giovanni's just south from you? It is easily the best Italian restaurant I have ever been to. The lady that owns it is probably 75 years old and has a million stories.

In reply to secretariata:

You had me at marl.

mazdeuce wrote: Geology wise Detroit is on the edge of an ancient ocean basin. That's why you get the massive evaporative salt deposits that underlie the Detroit area.

The salt mine is under Dearborn,too. 1200 feet down, so Alfa needs to monitor how far they're driving those piles.

alfadriver wrote: I know that part- but are they resting on bedrock or just the friction?

Could be either or both. Typically, when bearing is poor, they drive piles into the ground until they either hit rock (if it's not too far down) or until "refusal", which basically means it's not going any farther no matter how many times they nail it with the driver.

Usually, on top of the piles they pour what are called grade beams - basically a reinforced concrete horizontal beam designed to span from pile to pile. Then they build the building on top of that, just like a big fat footing that's under your house. They will have pile caps under each column and most likely there will be a pile or group of piles under each column to take the axial load. Then there will be other piles distributed between to carry the grade beam.