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. |
Forms are being built on this north side for that final lift. |
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. |
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. |
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. |
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. |
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. |
So much work is going into this building, not just to preserve history, but to create it. |
8 comments:
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?
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.
What does it mean when you say, "poured under pressure?" What is the process of doing so, exactly?
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.
Did you also say in an earlier post that there will be an additive added to the concrete for those final lifts?
Yes, I did say that. The word I heard on Friday was "stabilizer." I think the additive is to keep the concrete from shrinking.
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!
Thank you for this very helpful information!
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