Unsaturated Problem Soils: Expansive and Collapsing - Assignment Example

A change in the moisture content causes clay minerals to swell or lose cohesion and collapse. This expansion and contraction have tremendously adverse effects on the landscape, namely roads and buildings, causing cracking of walls and foundations, and, thus, devaluing of the property in a remarkably short time. It also costs millions of money on repairs. Studies also show that expansive soils, when on slopes, can cause landslides. Care and treatment, therefore, has to be taken before construction of buildings on this soil.

Engineers have to carry out soil tests, in order to determine the nature of the soil, before commencing construction, due to the adverse effects of expansive soil. Expansive soil can also be detected just by direct observation. If the soil is found to be expansive, various treatments could be applied so as to avoid the effects of the expansive soil:1) Proper compactionThis involves compacting the subgrade at the appropriate moisture content. This will “produce a subgrade that absorbs less water, provides slightly higher strength, and will not expand or swell as much..”.

( ACPA, 2008).2) Selective Grading.Selective grading may be the most cost-effective method of treatment if expansive soils are not the predominant soil type along the roadway alignment. This will include blending and cross hauling. If the profile grade can be designed to keep expansive soils out of the top of the subgrade, (ACPA, 2008), selective grading may also be sufficient in controlling the shrink and swell potential.3) Chemical modification.This is used when the subgrade soils consist of primarily expansive soils, and it is not economical to import non-expansive soil.

This provides an effective means to control the shrink-swell potential of a soil. This method can also be economical on some projects, compared to selective grading.