In geotechnical engineering, we are concerned with the ground. The ground is composed of rock, soil, and fill. Rock, soil, and fill are all accumulations of particles. The differences are:
- Rock and soil was put there by earth’s processes
- Fill was put there by human activity
Rock is generally stronger than soil and fill. While soil and fill can be “disaggregated”, that is broken down into individual particles, by hand under water, rock cannot be broken down into individual particles by hand underwater. This is a key difference. One other way to distinguish soil and fill from rock is the strength of a specimen in an Unconfined Compression Test:
Rock behaves differently from soil and fill and so there are two separate areas of study, but with some overlap, dedicated to each:
- Soil mechanics: study of soil and fill, treating soil and fill as particles.
- Rock mechanics: study of rock behaviour.
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