Resistance of piles to compressive loads 223Mean (KN/m^2 ) Mean of values (KN/m^2 ) Characteristic all values (KN/m^2 )
BH1 BH2 BH3cushaft 85 115 130 110 95
cubase 75 80 90 95 754.58LORD, J. A., HAYWARD, T., and CLAYTON, C. R. I. Shaft friction of CFA piles in chalk, Construction
Industry Research and Information Association, Report No. PR86, 2003.
4.59NG, C. W. W., SIMONS, N., and MENZIES, B. A Short Course in Soil-Structure Engineering of Deep
Foundations, Excavations, and Tunnels, Thomas Telford, London, 2004, p. 86.
4.60PELLS, P. J. N. and TURNER, R. M. Elastic solutions for design and analysis of rock socketted piles,
Canadian Geotechnical Journal, 1979, Vol. 16, pp. 481–7.
4.61FELLENIUS, B. H. Down drag on piles in clay due to negative skin friction, Canadian Geotechnical
Journal, Vol. 9, No. 4, 1972, pp. 323–37.
4.62JOHANNESSEN, I. J. AND BJERRUM, L. Measurement of the compression of a steel pile to rock due
to settlement of the surrounding clay, Proceedings of the 6th International Conference, ISSMFE,
Montreal, Vol. 2, 1965, pp. 261–4.
4.63CLAESSEN, A. I. M. and HORVAT, E. Reducing negative skin friction with bitumen slip layers,
Journal of the Geotechnical Engineering Division, American Society of Civil Engineers, Vol.
100, No. GT8, August 1974, pp. 925–44.
4.10 Worked examples
Example 4.1
A precast concrete pile for a jetty structure is required to carry a dead load of 240 kN and
an imposed load of 110 kN both in compression, together with an uplift load of 200 kN.
The pile is driven through 7 m of very soft clay into a stiff boulder clay. Determine the
required penetration of the 350 350 mm pile into the stiff clay to carry the specified
loading. Undrained shear strength tests were made on samples from three boreholes with
the following results:
Settlements are not critical to the structural design of the jetty, therefore the penetration
can be calculated by permissible stress methods by applying a safety factor of 2.5 to the
calculated ultimate bearing resistance. The shaft resistance within the soft clay will be
ignored because of possible sea-bed erosion and lateral pile movements.
Required total pile resistance in stiff clay (240 110) 2.5 875 kN.To allow for possible lower than mean cuvalues at pile base level take cu 0.75
110 kN/m^2.
Ultimate base resistance 9 0.75 110 0.35^2 91 kN.
Load to be carried by shaft resistance in stiff clay 875 – 91 784 kN.Take a trial penetration of 10 m into the stiff day:
Average effective overburden pressure in layer (0.65 9.81 7) (1.1 9.81 5)
98 kN/m^2.