Foundation, Concrete and Earthquake Engineering

Black Cotton Soils in United States

In the previous post different aspects of black cotton soil and its distribution in India and Africa are discussed. Do you know the status of united states? This is not good one. Expansive soil mostly black cotton soils are present throughout the world and are known in every US state. Even though united states is motherland of different standards and development of enriched codes (ASTM, ASCE,ACI, AASHTO,FEMA,NISC, ANSI and many other) every year expansive soil cause billions of dollars in damage to infrastructure. The American Society of Civil Engineers estimates that 1/4 of all homes in the United States have some damage caused by expansive soils. In a typical year in the United States they cause a greater financial loss to property owners than earthquakes, floods, hurricanes and tornadoes combined.

Even though expansive soils cause enormous amounts of damage most people have never heard of them. This is because their damage is done slowly and cannot be attributed to a specific event. The damage done by expansive soils is then attributed to poor construction practices or a misconception that all buildings experience this type of damage as they age.

Expansive soils are soils that expand when water is added, and shrink when they dry out. This continuous change in soil volume can cause homes built on this soil to move unevenly and crack. Often, damage from expansive soils can be seen within the first few months or years after a home is constructed. Each year in the United States, expansive soils cause $2.3 billion in damage to houses, other buildings, roads, pipelines, and other structures. This is more than twice the damage from floods, hurricanes, tornadoes, and earthquakes combined.
Distribution of Black Cotton ( Vertisols )Soil in North America
Distribution of Black Cotton ( Vertisols )Soil in North America
Although expansive soils can be found in almost every state and in Canada, the problems related to expansive soils are the most severe and widespread in California, Nevada, Arizona, Colorado, and other western and southern states.

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