Question

6. (a) In piling technology, explain the difference between a "displacement pile" and (2 marks) a "non-displacement pile". (b) Using graph paper, sketch 3 curves illustrating typical trends of variation of pile head resistance, shaft resistance and base resistance with increasing settlement, as expected from load testing a CFA pile in clay. Explain the differences between the three curves (6 marks) (c) A bored cast in-situ pile of 0.6 m diameter by 10 m long is installed through a 6 m thick layer of stiff clay overlying a dense sand layer as shown in Figure Q6 The sand layer extends to great depth. If the water table is located at ground level, calculate the ultimate bearing capacity of the pile using the charts in the Geotechnics Formula Booklet provided with this exam paper (Weltman and Healy, 1976, Berezantzex et. al. 1961). Take the lateral earth pressure coefficient Ks 0.7 for the sand-pile interface layer. (12 marks) Diameter 0.6 m Ground level Water table Stiff clay cu 200 kN/m2 Ysat 18 kN/m3 6m L= 10 m Dense sand Ysat 19 kN/m3 ø 360

Answer 1

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