The term expansive soil indicates to soils, which ahs the tendency to swell when their moisture

800 WordsApr 23, 20194 Pages
The term expansive soil indicates to soils, which ahs the tendency to swell when their moisture content is allowed to increase. The moisture may come from rain, flooding, leaking water or sewer lines, or from a reduction in surface evapotranspiration when an area is covered by a building or pavement. The term cracking soils is also used for these soils as they have the tendency to shrink and crack when the moisture is allowed to decrease. Soils containing the clay mineral montmorillonite generally show these properties (Komine and Ogata, 1996; Rao and Triphaty, 2003; Sivapullaiah et al. 1996; Wayne et al. 1984). There are many correlations that are useful in identifying potentially expansive soils. It may also be possible to identify them…show more content…
The higher the amount of monovalent cations absorbed to the clay mineral (e.g. sodium), the more severe the expansive soil problem (Fredlund and Rahardjo, 1993). The problems with foundations on expansive soils have included heaving, cracking and break-up of pavements, roadways, building foundations, slab-on-grade members, channel and reservoir linings, irrigation systems, water lines, and sewer lines (Cokca, 2001). Expansive soils have been reported from many parts of the world, mainly in the arid or semi-arid regions of the tropical and temperate zones like Africa, Australia, India, South America, United States, and some regions in Canada. This never means that expansive soils do not exist elsewhere, because they can be found almost everywhere. However, in the humid regions water tables are generally at shallow depth and moisture changes, which are responsible for volume changes in soils, are minimal excepting under extended drought conditions (Arnold, 1984; Shuai and Fredlund, 1998; Wayne et al. 1984). It is reported that damage to the structures due to expansive soils has been the most costly natural hazard in some countries (in United States more than the cost of damage from floods, hurricanes, tornadoes, and earthquakes on an average annual basis) for years (Kehew, 1995; Shuai and Fredlund, 1998). The particles of clays have highly negative-charged surfaces that attract free cations (i.e., positive-charged ions) and water dipoles. As a result, a highly
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