COMPARISON OF COARSE-GRAINED AND FINE-GRAINED SOILS
Coarse-grained soils have good load-bearing capacities and good drainage qualities, and their strength and volume change characteristics are not signifi cantly affected by change in moisture conditions under static loading. They are practically incompressible when dense, but signifi cant volume changes can occur when they are loose.
Vibrations accentuate volume changes in loose, coarse-grained soils by rearranging the soil fabric into a dense confi guration.Fine-grained soils have poor load-bearing capacities compared with coarse-grained soils. Finegrained soils are practically impermeable, change volume and strength with variations in moisture conditions, and are susceptible to frost. The engineering properties of coarse-grained soils are controlled mainly by the grain size of the particles and their structural arrangement.
The engineering properties of fi ne-grained soils are controlled by mineralogical factors rather than grain size. Thin layers of fi ne-grained soils, even within thick deposits of coarse-grained soils, have been responsible for many geotechnical failures, and therefore you need to pay special attention to fi ne-grained soils. In this book, we will deal with soil as a construction and a foundation material.
We will not consider soils containing organic material or the parent material of soils, rock. We will label our soils as engineering soils to distinguish our consideration of soils from that of geologists, agronomists, and soil scientists, who have additional interests in soils not related to construction activities.
THE ESSENTIAL POINTS ARE:
1. Fine-grained soils have much larger surface areas than coarse-grained soils and are responsible for the major physical and mechanical differences between coarse-grained and fi ne-grained soils.
2. The engineering properties of fi ne-grained soils depend mainly on mineralogical factors.
3. Coarse-grained soils have good load-bearing capacities and good drainage qualities, and their strength and volume-change characteristics are not signifi cantly affected by changes in moisture conditions.
4. Fine-grained soils have poor load-bearing capacities and poor drainage qualities, and their strength and volume-change characteristics are signifi cantly affected by changes in moisture conditions.