Domes provide many bulk-storage advantages, and customers also have multiple foundation options. The most common are detailed below:
- For sites with preferable or acceptable soil conditions, a ringbeam provides a shallow foundation alternative. Where applicable, the frost depth will determine the ringbeam’s depth, but usually the ringbeam is placed two to four feet in the ground.
- For sites where the top six to eight feet of ground is of less-than-ideal material, crews excavate the material, replacing it with controlled structural fill. This model allows for some settlement, but the amount will be within tolerable parameters for a dome.
- When the top 15 to 50 feet of soil is questionable, stone columns are often a workable option. First, crews use an auger to remove earth in about a 30-inch diameter hole until a more stable, soil-bearing layer is reached. Rock then fills the hole and is compacted, increasing the stiffness of the soil below the DomeSilo.
For areas where deeper foundations are required, other systems are available:
- In a piled-raft system, steel or precast concrete piles are driven into the ground. A layer of crushed rock three feet thick is layered on top, along with a fabric geogrid, which stiffens the rock mat and adequately strengthens the soil for the structure to be built on top.
- Piles are driven and are topped with a heavily reinforced concrete pile cap; in this model, the system is designed to bear on those piles, so the structure is essentially supported by stilts although built at ground level.
- Soil mixing is an option when soil is questionable for as much as 30 feet of depth. An auger is used to mix the soil with cement and lime; the mixture is then compacted.
- In sites with high water tables, a six-inch-wide piece of plastic called a wick drain provides a way for water to escape in areas of low permeability. A wick drain is driven vertically into the ground to the desired depth, and water flows to this strip, which acts as a channel that helps remove excess water. Consolidation of this soil is achieved over time with a surcharge loading.
- Dynamic compaction requires the use of a crane; a heavy weight is lifted and dropped repeatedly to densify soil.
Each of these methods requires different installation times and associated costs. Based on soil conditions, Dome Technology’s engineering team can identify the solutions most likely to work for a project. For a dome that doesn’t require deep foundations, customers can expect substantial savings. Contact our team for more information and to discuss your upcoming project.