Deserves to be reposted in this thread.
zeezrom wrote:Hello Porter,
I have taken the liberty of designing this stone box. Please refer to the figure below. I need to explain a couple of things. This is an extremely challenging design! I have designed many buried vault structures in my career and this one takes the cake. Typical design life requirements are around 50 years. I have never before designed any structure that must be guaranteed to survive more than 90 years. A structure like this would need to be stout indeed to be guaranteed for 1400 years, Good God!
Here are the issues at hand:
1. Groundwater: Every time it rains, water will percolate through the ground in a downward and downhill direction until it hits the shallow groundwater aquifer. Hopefully, this box is not sitting in the shallow aquifer or we are in deep crap. Let's assume the aquifer is deeper than the box - okay since this is a hill. Without some sort of drain rock around the structure, water will make it's way into the box. This is absolutely unacceptable! Water inside the box will kill everything in the box due to corrosion and freeze-thaw cycles. We need some sort of conduits to convey groundwater away from below the box. How will he have built these? With hollowed timbers? Sealed with sheepskin oil? Oh brother. I have no idea how to keep all moisture out of this box. We are screwed! But let me continue.
2. Seismic movement: In case of earthquakes and tremors, we need to design a structure that can withstand lateral and vertical movement. Bricks are just about the worst thing you can use for such a scenario. Reinforcement with a ductile material (steel) is preferred but I can't think of how in the hell Moroni is going to get that so I'm thinking we should just make the walls beefier. Currently, I'm showing blocks that are 24 inches thick and 10 inches high. In reality, we should double up the bricks because this box would likely fail in a 7+ seismic event. This means we should make the walls 48 inches thick - just to make sure. Hey, if I'm stamping this drawing, I need to make sure it's done right.
3. Lateral movement due to erosion: Over the long period of 1400 years, a large amount of sediment will likely be transported down the hill. I'm assuming the box was built about half way up the hill so sediments from the top of the hill would work their way down over the years. This is a very iffy assumption. I really have no idea whether we are gaining sediment or losing sediment due to erosion. But since the top of the box was buried with dirt in order to hide it from the world, I'll assume sediments accumulated above the box. This lateral movement of water and sediments will present a constant force on the uphill wall of the box. We need beefy walls to support this. Not only that, but without reinforcement in the walls, we must rely on the weight of the bricks to keep the wall together. I'm not comfortable relying on that!
4. Lateral earth pressure: the in-situ horizontal pressure exerted on the 4 walls is taken care of by installing structural backfill around the walls and ensuring that the groundwater is drained away from the structure. A larger foundation below the box will help support the walls under this lateral pressure. Without obtaining soil samples, I cannot design this but we will assume a design for now.
5. Box lid: I'm very concerned about this lid. Where am I going to find a stone that is only 12 inches thick but that can span nearly 4 feet in two directions for 1400 years! I wish the lid could be thicker but I don't know how Joseph Smith could move it if we made it thicker. Maybe Moroni helped him move it? How would Moroni get this lid up the hill? Poor guy...
BCSpace. You're an engineer. Do you have a response to this?
