Which soil type is preferred for foundation design?

For foundation design, predominantly coarse-grained soils are preferred due to their superior drainage characteristics and stability. Coarse-grained soils, which include gravel and sand, typically have larger particle sizes that allow water to drain quickly through them. This drainage reduces the risk of hydrostatic pressure building up beneath the foundation, which can lead to settlement or structural issues over time.

Coarse-grained soils also provide better load-bearing capacity compared to finer soils because their larger particles interlock more effectively, distributing loads more evenly. This property is crucial for the stability and integrity of foundations, especially in environments with fluctuating moisture levels and varying loads from structures above.

In contrast, predominantly clayey and silty soils can be problematic for foundations. Clay soils often expand and contract significantly with moisture changes, which can cause movement and deformation in a foundation. Silty soils can retain water and lead to increased pore pressure, which may weaken the soil's ability to support loads. Predominantly sandy soils, while better than clay and silt in terms of drainage and load-bearing capacity, can be too loose and prone to shifting under heavier loads, particularly when saturated.

Thus, the preference for predominantly coarse-grained soils ensures a stable foundation that mitigates potential problems associated with moisture and