Mechanical Properties of Soils

Soil has a surprisingly diverse set of mechanical properties. The empirical and theoretical study of soil mechanics has progressed to the point where soil engineers are able to consider a wide variety of mechanical properties when they design structures that involve large quantities of soil. Soil mechanics has applications in everything from major civil engineering projects to backyard landscaping.

Shear strength refers to the level of shear stresses a material can resist without fracture. Shear strength is measured in Newtons per meter squared. Shear stresses are forces that are applied tangentially along a face of the soil. Shear strength is difficult to measure as it depends on a wide variety of factors, including the nature of the soil, the history of the particular soil sample to be measured, and the rate at which the shear forces are applied.

Lateral earth pressure is the pressure that earth exerts horizontally. If you have a cubic mass of soil held in a cubic container, then lateral earth pressure is the pressure exerted on the walls of the container. Lateral earth pressure is measured in Pascals, or Newtons per meter squared.

Consolidation is the process whereby soil volume decreases under the application of a load. Consolidation is caused by loads being applied to soil and the grains of soil being packed together more closely as a result.

Bearing capacity is the capacity of the earth around a structure to support applied loads. Bearing capacity is measured in Pascals or Newtons per meter squared.

Permeability refers to the ease with which fluid can flow through the pores in soil. Permeability is measured in meters squared or Darcys. Seepage refers to the rate at which fluid moves through a mass of soil. Seepage is measured in meters per second.

Slope stability refers to the resistance of a slope to failure or collapse. The stability of a slope encompasses a wide variety of considerations and does not have a single, universal unit of measurement.