Civil and Building Engineering.

Soil and rock are descriptive terms that have different meanings, depending on their community of use. The following subsections present a few of the more common definitions.

Soil To a farmer, soil is the earthen material that supports life.
To a geologist, soil is an ambiguous term.
To an engineer, soil is a granular material plus the intergranular gas and fluids. This includes clay, silt, sand, and gravel. It may also contain anything found in a landfill: household waste, cinders, ashes, bedsprings, tin cans, old papers, and so on.

Rock To an engineer, rock is any individual material requiring blasting or another brute-force method to excavate. It is also classified as any material with a compressive strength greater than 725 psi (5.0 MPa). This definition is complicated by the presence of structures or defects that weaken the rock mass. The vagueness of the terms describing rock is due to the wide variety of materials encountered and the different information needs of those who use the descriptive terms.

Problems in geotechnical engineering involving the use of rock and many soils can seldom be solved by blind reliance on empirical data gathered from past projects or on sophisticated computerized analyses. Each situation is unique and requires

•  Careful investigation.
•  Thorough analysis.
•  Engineering judgment based on varied experience.
•  Imagination to visualize the three-dimensional interplay of forces and reactions in complex systems.
•  Intuition to sense what cannot be deduced from scientific knowledge.
•  Initiative to devise new solutions for both old and new problems.
•  Courage to carry out the work to completion despite skeptics and the risk of the unknown.