The necessity of optimising the foundation design encourages the use of methods based on in situ test results in the design of pile foundations. For this purpose, a cone penetration test (CPT) is commonly used. Design methods developed over the last few decades may differ not only in factors used for correlating the cone resistance with bearing capacity of a given type of pile foundation, but also in adoption of the representative cone resistance value for the calculations. Contrary to the design of pile foundation in relatively homogeneous ground conditions, in the case of heterogeneous stratification, the influence of the quality of test itself and the adoption of the average cone resistance for the calculation may have significant impact on the result. This is especially important issue when weaker strata, which may affect the end-bearing capacity, is present just below the pile, in its area of influence. The article presents some of the methods of averaging the measured cone resistance, how they may affect the obtained results and other factors affecting mainly end-bearing capacity of a single compressed pile.

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