Effect of Local Loss of Support on Foundation Design

The development of small sinkholes, excavation for temporary repairs, erosion by ground water, or compaction resulting from vibrations may cause a local subsidence beneath foundation structures. This subsidence eliminates the soil support beneath a portion of the foundation. By the use of the theory of elastic subgrade reaction, a study was made for beams and slabs that span gaps in the elastic subgrade. In order to simplify the computations, curves have been prepared that may be used for design. The use of these curves is illustrated by examples of a footing spanning a void and of a slab spanning a circular void corresponding to a small sinkhole.