Saturday, November 17, 2012

Ultimate Bearing Capacity of Soil: Strip Footings.

Strip Footings
Terzaghi developed his bearing capacity equation for strip footings by analyzing the forces acting on the wedge abc in Fig. 12.6. The equation for the ultimate bearing capacity qu is

where Qult = ultimate load per unit length of footing, c = unit cohesion, γ the effective unit weight  soil, B = width of footing, D,= depth of foundation, Nc, Nq and Nγ are the bearing capacity factor

They are functions of the angle of friction, Ø.

The bearing capacity factors are expressed by the following equations

where Kpy = passive earth pressure coefficient

Table 12.1 gives the values of Nc, Nq and Nγ for various values of Ø and Fig. 12.7 gives the same in a graphical form.

Table 12.1 Bearing capacity factors of Terzaghi

Figure 12.7 Terzaghi's bearing capacity factors for general shear failure

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