The characteristics of expansive and collapsible soils, and considerations for foundation design and construction.
Expansive Soils Definition Expansive soils refer to soils or unconsolidated mudstones containning a significant amount of montmorillonite caly materials, These soils experience expansion when water is absorbed, or develop swelling pressure when constrained. Identification Method Expansive Potential (EP) = 0.003 x Z x Sw > 0.5 (Expansive soils) Z : Depth of the expansive layer Sw = (Height of expansion due to water absorption (∆H)) / (Height of the sample(H)) x 100% Characteristics The Soil exhibits significant expansion upon moisture absorption. When constrained, the soil develops swelling pressure. The soil is highly compressible when dry. High plasticity soil Liquid Limit (LL) ≥ 40 Plasticity Index (PI) ≥ 15 These soils are geotechnically very unstable Consideration for Foundation Design and Construction Magnitude of swelling pressure: Place the sample in a consolidation apparatus and supply water. The maximum load at which no sample expansion occurs i...