Slope Analysis 18 Hay St

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Where footings found into very stiff natural clays, they may be dimensioned for a maximum allowable bearing
pressure of 100 kPa. Based on the bore logs, the above material is encountered at approximately 0.7 m to 2 m depth.
The ultimate geotechnical end bearing and shaft adhesion parameter are presented in Table 3. The values given will
need to reduced by applying a suitable geotechnical strength reduction factor (Φg) for limit state or divided by a
suitable factor of safety for working stress methods. The Φg should be selected by the designer.


TABLE 3: DEEP LEVEL FOOTING – ULTIMATE GEOTECHNICAL PARAMETERS (LONG PILE)

                              Material                                  Fb (kPa)                     Fs (kPa)
                           Very Stiff CLAY                                 450                           30
 Notes: Fb = Base Bearing (Ultimate); Fs = Shaft Adhesion (Ultimate)


The upper 1 m of soil profile should be ignored in shaft calculations to allow for shrinkage cracks. The values
presented in Table 3 assume that the material equal to four pile diameters below the base of any footings is as strong
or stronger.
Settlement values are subjected to a variety of factors; however, a properly designed and constructed pile should
have a serviceability settlement between 1% and 2% of its’ diameter.




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