is a branch of soil physics and engineering mechanics that describes the behavior of soils. It differs from fluid mechanics and solid mechanics in the sense that soils consist of a heterogeneous
mixture of fluids (usually air and water) and particles (usually clay, silt, sand, and gravel) but soil may also contain organic
solids and other matter. Along with rock mechanics, soil mechanics provides the theoretical basis for analysis in geotechnical engineering, a subdiscipline of civil engineering, and engineering geology, a subdiscipline of geology. Soil mechanics is used to analyze the deformations of and flow of fluids within natural and man-made structures that are supported on or made of soil, or structures that are buried in soils. Example applications are building and bridge
foundations, retaining walls, dams, and buried pipeline
systems. Principles of soil mechanics are also used in related disciplines such as engineering geology, geophysical engineering, coastal engineering, agricultural engineering, hydrology and soil physics.
This article describes the genesis and composition
of soil, the distinction between pore water pressure
and inter-granular effective stress
, capillary action of fluids in the soil pore spaces, soil classification
, time dependent change of volume due to squeezing water out of tiny pore spaces, also known as consolidation
, shear strength
and stiffness of soils. The shear strength of soils is primarily derived from friction between the particles and interlocking, which are very sensitive to the effective stress. The article concludes with some examples of applications of the principles of soil mechanics such as slope stability
, lateral earth pressure on retaining walls, and bearing
capacity of foundations.