In determining the bearing capacity of shallow strip footings under earthquake loading conditions, most seismic codes neglect the effect of the inertia of the soil mass underneath a footing. Seismic acceleration is considered to be acting on the structure only. In this Paper, the seismic bearing capacity factors (Nq, Nc and Ngamma) are determined by using the limit equilibrium technique of slope stability analysis with inclined slices. The analysis shows that the factor Nq is dependent on the inertia of the surcharge load; the relationship between Nc and Nq given in the literature is found to be incorrect for inclined loads and the inertia of the soil mass certainly has an effect on Ngamma. Results of the analysis are shown in graphical forms as functions of the horizontal acceleration factor and of the angle of internal friction of the soil. The analysis does not include the effect of the excess pore water pressure generated by the earthquake. For small accelerations, smaller than O.1g, the effect of the inertia of the soil mass is small and is accommodated within the factor of safety. For large accelerations, larger than the critical acceleration (i.e. the acceleration needed for incipient failure for a given vertical load), the deformation of the footing may be estimated by the sliding block technique. However, the use of the sliding block technique is restricted to soils which do not lose strength with deformation. (A)

  • Availability:
  • Corporate Authors:

    Thomas Telford Limited

    London,   United Kingdom 
  • Authors:
    • Sarma, S K
    • Iossifelis, I S
  • Publication Date: 1990-6


  • Undetermined

Media Info

  • Pagination: p. 265-273
  • Serial:
    • Volume: 40
    • Issue Number: 2
    • Publisher: Thomas Telford Limited
    • ISSN: 0016-8505

Subject/Index Terms

Filing Info

  • Accession Number: 00606883
  • Record Type: Publication
  • Source Agency: Transport and Road Research Laboratory (TRRL)
  • Files: ITRD, TRIS
  • Created Date: Mar 31 1991 12:00AM