The Effect of the Grain-Size Distribution on Expansion and Collapse Behavior of Expansive Soils and Their Implications

Expansive soils are some of the most widely distributed and costly of geologic and building hazards. Expansive soils are fine-grained soils subject to changes in volume in response to wetting and drying. This work reports the effect of grain-size distribution of expansive soils on its volumetric behavior. This study is based on the experimental grain-size distribution of expansive fine-grained (EX) and coarse-grained (C) soils. It is concluded that there is a direct relationship, on one hand, between expansion and the content of fine-grained soils and, on the other hand, between collapse and the content of coarse-grained soils. Collapse occurs almost immediately and depends on the amount of coarse particles of soils. Natural soils that have been classified as showing high to very high expansive potential based exclusively on their gradation and plasticity should be considered as possible collapsing soils. All tested soils showed a predominant behavior (expansion or collapse) dependent on their grain-size distribution. The mixtures of expansive (fine-grained particles) and collapsing soils (coarse-grained particles) showed that expansion and collapse almost nullified each other at certain dosage. Therefore, this procedure could be used as an alternative technique for volumetric stabilization of expansive and collapsing soils. The experimental results indicate that a mixture 30% C–70% EX shows the lowest volumetric deformation for the tested soils. To apply this technique in construction sites, it is suggested to mix the soils at the dosage recommended by the laboratory, then homogenize and finally compact the material in the site. This proposal is ecological and sustainable since it uses problematic natural soils that are generally discarded in construction.