The lowest part of a structure which transmits its weight to the underlying soil or rock is the foundation. Foundations can be classified into two major categories: that is, shallow foundations and deep foundations. Individual footings (Fig.  1.1) square or rectangular in plan which support columns, and strip footings which support walls and other similar structures are generally referred to as shallow foundations.  Mat foundations, also considered shallow foundations, are reinforced concrete slabs of considerable structural rigidity which support a number of columns and wall loads. When the soil located immediately below a given structure is weak, the load of the structure may be transmitted to a greater depth by  piles and  drilled shafts, which are considered  deep foundations. This book is a compilation of the theoretical and experimental evaluations presently available in literature as they relate to the load-bearing capacity and settlement of shallow foundations.

The shallow foundation shown in Fig. 1.1 has a width  B and a length L.

The depth of embedment below the ground surface is equal to Df  Theoretically, when B/L is equal to zero (that is, L = ), a plane strain case will exist in the soil mass supporting the foundation. For most practical cases when B/L <=1/5 to 1/6, the plane strain theories will yield fairly good results. Terzaghi [1] defined a shallow foundation as one in which the depth, Df , is less than or equal to the width B (Df /B " 1). However, research studies conducted since then have shown that, for shallow foundations, Df /B can be as large as 3 to 4.

FIGURE 1.1   Individual footing


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