From a professional analysis of our bolted time capsule containers:
A time capsule buried in dry soil will not experience an even pressure distribution, as it would if it were suspended in a liquid or a gas. With the capsule oriented vertically, the primary loads would be exerted on the top and bottom. Side loads would be insignificant, unless the soil were to become saturated with water and unstable. I assume you are not putting it in that kind of an environment. The 14x14x24" bolted time capsule can withstand loads in excess of 200 lbs distributed over each of the 14" x 24" sides without significant deflection. In addition, it can sustain a vertical load well in excess of 10,000 lbs distributed over the top surface.