Friday, July 12, 2013

Gable Stones, Foundation Work and Trivia

I was delighted to arrive at the site late this afternoon and see the crane operator climbing down after a long day at work.
The northwest corner of the foundation received an early pour this morning.
When I arrived 12 hours later, Jacobsen workmen were removing the forms.  Notice the gap between the vertical piers on this corner.  The engineering design allowed for the foundation to turn a corner here.  Also notice the space between the foundation level which was poured this morning, and the orange mesh which marks the ground level of the tabernacle.  This final level or lift will be poured soon.
 Forms are being built on this north side for that final lift.
The area which I call the west porch has received a thick layer of rebar.  My visiting engineer-son was with me on my visit to the site today.  He taught me that rebar is short for reinforcing bar, which of course makes complete sense.
Over the last few months, the engineering details surrounding the micropiles, shown here in the west lot, have gone right over my head.  My son, and my engineer-husband, who was also with us at the site, patiently explained it to me after we returned home.  There were 411 micropiles drilled into the foundation floor in March.  They are 25 feet deep, where the exterior piers are 90 feet deep.  The micropiles drilled along the edge of the foundation are compression piles.  Once the enormous weight of the tabernacle shell is moved from the piers to the new foundation walls, the compression piles will support the foundation walls and hold the shell up.  However, the water table left over from Lake Bonneville wants to push up the new floor of the basement.  The micropiles in the center of the slab floor hold down the floor with tension.  Together, these 411 micropiles hold up the walls with compression and hold down the floor with tension.
This view of the west lot is from the north.  This will all be underground parking.  You can see the entrance to this lot just to the right of the center of this picture.  The slump in the fenced area on the left will collect dirty water accumulating over time from the cars in the garage.  The slump allows a place where the oil and dirt can be separated out before the water enters the city storm water system.
I learned more about the membrane which I often mention.  You can see the most important part of the "system" in the lower left corner of this picture.  This is applied to the concrete slab under very high temperatures, which of course is difficult work in our 90 degree weather.  This is then covered with what looks like black tar paper which protects membrane.  This membrane is being applied to every exterior concrete surface and will keep the new temple dry.
I also learned a few details about the barrier walls which surround the site.  Two rows of tie-backs can be seen here.  The barriers are built as the lots are excavated to keep the walls in place.
Twenty-foot long soil nails are drilled into the barriers and then filled with grout.  This picture shows a puddle of grout below the tie-back.  We've been seeing this all around the lot as the barriers have been built, but I haven't completely understood what was happening until now.
The barrier walls can be easily seen here in the south lot, which is still being excavated.
I saw these stones several months ago but did not know what they were.  Tonight I learned that they came from the gables which fell during the 2010 fire.
This west gable is the only one remaining.  The stones will be reused when the new gables are restored.
This is the south face without its gable. 
The flowable fill has been poured on three sides of the tabernacle.  This picture shows the east side, with a nice glimpse into the basement.  
This picture shows the foundation at the southeast corner.  It is very different than the foundation corners on the west side.
 I am learning how to recognize the difference between the north and south faces.  The only opening in the north foundation face at the first basement level is in the center which will connect to the annex.
The north foundation has an entrance into the lowest level of the basement, see here on the left side of the picture.  Ultimately, this will be an elevator  leading from the annex to the lowest basement level.
This will be the north annex.  The plans filed with the City of Provo show that this area will have dressing rooms.  While I have now seen the plans, they are proprietary, so I was not allowed to copy them in any way.  I have to go from memory.
This view of the north lot from the east shows the space between the north annex wall and the barrier wall.  Ultimately, the concrete will be covered with the membrane system and then this space will be back-filled.  Farther west in this photo you can see the Nu Skin campus.
It's easy to envision how the annex will connect to the lowest level of the basement from this view.
When the temple is completed, the annex will be completely underground.
The south lot will be underground parking.  The depth on the right is close to the final excavation level.
This foundation on the south has several openings along its face.  The red ladder marks the doorway where patrons will enter from underground parking.  The opening on the left is a doorway to underground office space outside the footprint of the original tabernacle. 
You can easily see the last level, or lift, of the foundation which will be poured.  This concrete will be a special mixture poured under pressure.
Notice again that the foundation walls are built out on the west side.
There are two things to observe in this photo.  The first is the glimpse I got into the interior.  The top of the pier you can see through the doorway marks the lowest level of the tabernacle shell.  The second thing to see is the horizontal opening in the concrete face in the center of the photo.  This is where the slab from the underground garage will meet the temple.
That horizontal opening can be seen along the bottom of this foundation wall.  Remember that just a week or two ago, there was another level of foundation wall showing, but it has been covered with the flowable fill.
I'm going to try to be at the site when this last lift is poured.  The next big step, and it seems like everything is a big step, is to transfer the weight of the tabernacle shell from the 90-foot piers to the foundation walls.  The piers will then be cut away, inside and out.
So much work is going into this building, not just to preserve history, but to create it.


dSquared said...

It seems you had several pictures today from inside the fence. My guess is that you had help.

The piles tension / compression thing was great but I think I need a few more arrows.

So when the pylons are finally cut away, what keeps them from being a water conduit?

Julie Markham said...

You are observant. I did get a lovely and unexpected invitation which I could not refuse. I will work on explaining the tension and compression a little more, but you might have to find your own personal engineer to draw you some pictures, which is what finally helped me turn the corner. I happen to have asked about the pylons being cut away, and although it was a different question, the answer will help you. The piers will be cut off, and then another layer of slab will be added, plugging the holes. If it helps, once the piers are gone, they will obviously no longer be giving any support. The foundation walls, supported by the compression micropiles underneath them, will take over the weight of the massive tabernacle shell. The tension micropiles in the center of the slab will keep the slab floor from being pushed up by the water table. I hope that helps.

David said...

What does it mean when you say, "poured under pressure?" What is the process of doing so, exactly?

Julie Markham said...

I don't know how this is done, but I overheard the engineers talking. They said if the forms aren't tight during the pour, the concrete actually sprays out. What's important is that there is pressure involved so there are no gaps in the cement and the tabernacle shell will sit firmly on the new foundation.

Esperanza said...

Did you also say in an earlier post that there will be an additive added to the concrete for those final lifts?

Julie Markham said...

Yes, I did say that. The word I heard on Friday was "stabilizer." I think the additive is to keep the concrete from shrinking.

Anonymous said...

Julie, I talked to a concrete worker the other day about the process of the third lift being poured under pressure. He explained to me that a valve system is set up on the cement forms and the cement is then injected into the space with pressure. Once it has filled the area or space and a certain pressure is reached the injection process stops and the valve then closes keeping the pressure inside. The worker said it is actually one of the easier pours. In addition I wanted to make note regarding the question of what happens when the piers are cut off and if water will come up from below. Well, these piers are already filled with re-bar and concrete--all 90 feet of it. Water will would have a very difficult time getting any headway in that. Plus, I am sure a protective membrane will be placed over it when it is cut off and before a cement pour covers over them as well. One day one of the engineers really had a good way of explaining it to me (in layman' terms) when I asked about how all the water is going to be kept out. He said that with the multiple layers of concrete and barriers they are creating, just imagine this all as giant bathtub. That was great!

Julie Markham said...

Thank you for this very helpful information!