关键词: 单桩承载力, 特征值, 极限值, 浮重度, 有效长度, 抗拔系数

Abstract: 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.

Key words: bearing capacity of pile, characteristic value, ultimate value, buoyant unit weight, effective length, tension coefficient