4.3: TERZAGHI'S BEARING CAPACITY THEORY
4.3 TERZAGHI'S BEARING CAPACITY THEORY
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:
-
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). -
Zones acd and bcf. These zones are referred to as Prandtl's radial shear zones.
-
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...