A granulate mattress is a thick, compacted layer of granulate or crushed stone that distributes loads evenly over the subsoil. The mattress is often reinforced with one or more layers of geogrid or geotextile, creating a stiff, load-bearing layer over weak or uneven ground.
How it works
The granulate mattress acts as a spreading intermediate layer. Point loads and uneven loads are distributed within the mattress, so that the pressure on the underlying soil becomes more uniform. In combination with piles, a pile mattress is formed: the mattress carries the load to the piles through arching action, while the soft soil in between is relieved.
Application
- Pile mattress system — as load distribution over a field of piles under roads, embankments and floors
- Roads and railways on soft ground — to limit settlement and differential settlement
- Industrial floors and paving — as a load-bearing base
- Soil improvement — where piling or soil replacement is too expensive
Advantages
- Distributes loads and limits differential settlement
- Faster and sometimes cheaper than heavy foundation structures
- Uses reusable granulate
Point of attention
The thickness, grading and type of geogrid must be determined by a structural engineer based on load and ground conditions.
Related Terms
- Granulate
- Pile mattress
- Geogrid
- Soil improvement
- Foundation
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