SHALLOW FOUNDATIONS
This Geotechnical Engineering Circular (GEC) coalesces more than four decades of research, development and practical experience in the application of shallow foundations for support of ransportation structures. The document is intended to be a definitive desk reference for the transportation professional responsible for esign, procurement and construction of shallow foundations for bridges and other transportation-related structures.
This GEC draws heavily from previous published work by the Federal Highway Administration (FHWA), State (and Local) Highway Agencies (SHAs) and other authors of practical guidance
related to shallow foundations. As such, this document generally does not represent “new” research but is intended to provide a single reference source for state-of-the-practice information
on the design and construction of shallow foundations.
The one exception to the foregoing statement is in the area of bridge support on shallow foundations bearing on compacted structural fills. Special attention has been given to case
histories and design examples on the use of shallow foundations to support abutments in compacted approach embankments.
Shallow foundations represent the simplest form of load transfer from a structure to the ground beneath. They are typically constructed with generally small excavations into the ground, do not require specialized construction equipment or tools, and are relatively inexpensive. In most cases, shallow foundations are the most cost-effective choice for support of a structure. Your house is most likely supported on shallow spread footings, and you probably supported that deck you constructed last year on pre-cast concrete pier blocks because they were inexpensive and easy to place. Bridges, however, are frequently supported on deep foundations such as driven piling.
This may be as much a result of the continued use of past practice than for any other reason and has its roots not in highway construction, but railroads. The need to maintain constant and reliable grades over vastly differing ground conditions and topography made the choice to support virtually all railroad bridges on piles rather obvious. At the time of rapid rail expansion in North America, and all over the world, the concepts of soil mechanics and geotechnical engineering had not even been conceived. Railroad engineers needed a reliable way to support bridges and trestles, and the available technology directed them to driven piles.