The designing and calculating methods for compressive bearing capacity of a single pile can be divided into two types

i.e. characteristic value method and ultimate value method

in the Chinese codes related to pile foundations. The bearing capacity of a single pile is obtained by directly summarizing the skin friction and the tip resistance. These methods have some conceptual and theoretical disadvantages

since the skin friction and tip resistance cannot be simultaneously mobilized due to different mechanical responses and deformation requirements at the pile skin and the pile tip. The ultimate value method is more direct

reliable

accurate and clear in concept

and is more ready to be used in parallel to international standards. Hence it is suggested here that this method is preferred in the standards. A contradiction may occur in determining the uplift bearing capacity of a single pile according to the results of pull-out tests using the different standards. Because of this

the natural unit weight of pile should be used in calculation

instead of the buoyant unit weight of pile. Further research should be conducted to explore the following two phenomena in revising the relevant codes: one is that the unit skin friction decreases when exceeding the effective length of the pile

and the other is that tension coefficients for pull-out pile in some engineering is far less than the recommended values in the relevant codes

especially when pile length is longer.