• Bearing Capacity of Soil and its Factor of Safety

    by  • March 19, 2014 • Building Construction, Soil Mechanics • 0 Comments



    Bearing capacity of soils are reduced by a factor called factor of Safety to underestimate the bearing capacity of soils. This value of factor of safety depends on following factors:

    1.  Type of soil

    2.  Method of exploration

    3.  Level of Uncertainty in Soil Strength

    4.  Importance of structure and consequences of failure

    5.  Likelihood of design load occurrence, etc.

    Generally a factor of safety F = 3 is assumed for bearing capacity calculations,  unless otherwise specified for bearing capacity problems. Table-1 gives the details of factors of safety to be used under different circumstances.

    Fig: Effect of Bearing Capacity of Soil on Foundation

    Fig: Effect of Bearing Capacity of Soil on Foundation

    Table-1: Typical factors of safety  for bearing capacity  calculation in different situations

    Category Typicalstructures Characteristics of the category Design factor of safety
    Thorough and completesoil exploration Limited soil exploration
    A Railway bridges, warehouses, blast furnaces, hydraulic, retaining walls, silos Maximum design load likely to occur often,

    consequences of failure – disastrous

    3.0 4.0
    B Highway bridges, light industrial and public buildings Maximum design loads may occur occasionally,

    consequence of failure – serious

    2.5 3.5
    C Apartment and office buildings Maximum design load unlikely to occur 2.0 3.0