UPDATING BEARING CAPACITY - SPT GRAPHS

The graphs used by the Maryland State Highway Administration (MD SHA) for determining the allowable bearing capacity of shallow foundations related the Standard Penetration Test (SPT) in blows/ft to the maximum advisable presumptive bearing value. The major drawbacks to the use of these graphs are that they do not consider the effects of the depth, shape and the size of the footing, the location of the water table, and the factor of safety. The graphs are very conservative, which suggests that they do not provide accurate, cost effective designs, and in the case of a high water table they provide unsafe values, however, their main advantage is that they are simple to use. In this study, new graphs were developed to determine the bearing capacity of shallow foundations as a function of the SPT N-value. The new graphs consider the effect of depth, size and shape of the footing, type of soil, factor of safety and the location of the water table. The new graphs are based on the American Association of State Highway and Transportation Officials (AASHTO) bearing capacity equations. Although the goal of the present study is to produce charts providing quick estimates of the bearing capacity and not the values to be used in final design, one should not forget that settlement is a controlling mechanism in foundation design and was not addressed within the scope of this project.

• Corporate Authors:

  University of Maryland, College Park

  Department of Civil and Environmental Engineering
  College Park, MD  United States  20742

  Maryland Department of Transportation

  State Highway Administration, 707 N Calvert Street
  Baltimore, MD  United States  21202
• Authors:
  • Aggour, M S
• Publication Date: 2002-3-15

Language

• English

Media Info

• Pagination: 88 p.

Subject/Index Terms

• TRT Terms: Accuracy; Bearing capacity; Cohesive soils; Cost effectiveness; Depth; Design; Footings; Granular soils; Graphs; Safety factors; Shape; Size; Soil penetration test; Water table
• Identifier Terms: American Association of State Highway and Transportation Officials
• Subject Areas: Design; Geotechnology; Highways; Hydraulics and Hydrology; Safety and Human Factors; I42: Soil Mechanics;

Filing Info

• Accession Number: 00960447
• Record Type: Publication
• Report/Paper Numbers: MD02-007B49
• Files: TRIS, STATEDOT
• Created Date: Jul 15 2003 12:00AM