What are Expansive Soils?

Expansive Soils

Expansive soils, which are also known as swelling soils, are soils that assume a general volume increase when subjected to moisture. Basically, when water reaches these soils the soil soaks it up and expands.

Now the reason for this is that these swelling soils always contain clay minerals that attract and absorb water, so it’s these clay minerals that cause these soils to be expansive. Now, in many cases these expansive soils are buried under a layer of topsoil or dense vegetation.

Many times, geotechnical engineering firms, civil engineering firms, or sometimes construction companies will drill holes to collect samples. Then, these samples can be taken or sent to a lab where swelling potential is determined.

Now some places have a really high concentration of swelling soils, and there there’s a possibility that it could be required by law to have this laboratory analysis go on, it may be required by law for swelling potential to be determined.

A way to deal with the problems that expansive soils can bring about is by dewatering foundations of structures. Now another type of swelling material is known as swelling bedrock, so it’s similar to expansive soils, and swelling bedrock contains a rock called claystone.

When water is absorbed these clays or bedrock experience a large increase in internal pressure or an expansion of volume. That’s a look at expansive soils.

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by Mometrix Test Preparation | Last Updated: August 15, 2019