Soil Dilatation

Soil dilation is a change in volume when soil is subjected to shear deformations. In the honor of the person who described it for the first time it is also called Reynolds dilatancy. In simple words, granular material which are densely compacted naturally tends to dilate.

Quite the opposite, loose granular material continuously get denser under shear. If the volume decreases with increasing shear, is recognized as a dilative material.

All of us has experienced walking through a wet sandy soil. when we step on muddy soil we apply a compressive and a shear force on it. As a result sand beneath the shoes and its pore water moves to fill the new space between the soil particles.

The importance of soil dilatancy is that the growth of confining pressure, increases the friction angle of soil to a certain level and then abruptly reduce it. As a result, geotechnical structures such as soil slopes are in danger of collapse or instability if they are not designed based on dilatancy effect.