From Theoretical Foundation Engineering


Terzaghi (1943) proposed a well-conceived theory for determination of the ultimate bearing capacity of shallow rough rigid continuous (strip) foundations supported by a homogeneous soil layer extending to a great depth. Terzaghi defined a shallow foundation as a foundation for which the width of the foundation, B, is equal to or less than its depth, D f (Fig. 4.1a). The failure surface in soil at ultimate load, q u, per unit area of the foundation, as assumed by Terzaghi is shown in Fig. 4.6. Referring to Fig. 4.6, the failure area in the soil under the foundation can be divided into three major zones. They are:

  1. Zone abc. This is a triangular elastic zone located immediately below the bottom of the foundation. The inclination of of the sides ac and bc of the wedge with the horizontal is ? = ? (soil friction angle).

    Figure 4.5: Settlement at ultimate load for surface foundation on sand (after Vesic, 1963).

  2. Zones acd and bcf. These zones are referred to as Prandtl's radial shear zones.

  3. Zones ade and bfg. These zones are the Rankine passive pressure zones. The slip lines in these zones intersect the ground surface at {45- ?/2) with the horizontal.

Figure 4.6: Failure surface in soil at ultimate load for a continuous rough rigid foundation as assumed by Terzaghi (1943).

The lines cd and cf are...

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Topics of Interest

4.4 SOME OBSERVATIONS ON TERZAGHI'S BEARING CAPACITY THEORY It is obvious from Section 4.3 that Terzaghi's bearing capacity theory has been obtained by assuming general shear failure in soil. However...

4.11 FOUNDATIONS SUPPORTED BY A SOIL WITH A RIGID ROUGH BASE AT A LIMITED DEPTH The problem of bearing capacity of shallow rough foundations discussed in the preceding sections assume that the soil...

4.7 OTHER SOLUTIONS FOR BEARING CAPACITY FACTORS At this time, the general trend among geotechnical engineers is to accept the method of supposition as a proper means to estimate the ultimate bearing...

4.5 MEYERHOF'S BEARING CAPACITY THEORY In 1951, Meyerhof published a bearing capacity theory which can be applied to rough shallow and deep foundations. The failure surface at ultimate load under a...

4.9 BEARING CAPACITY OF FOUNDATIONS ON ANISOTROPIC SOIL EXTENDING TO A GREAT DEPTH Foundations on Sand ( c=0) Most natural deposits of cohesionless soil have an inherent anisotropic structure due to...