BEARING CAPACITY OF EXPANDED-BASE PILES IN SAND

The results of loading tests are used to develop empirical correlations between the point‐bearing resistance of expanded‐base piles and the results of standard penetration tests. The resistance is shown to be proportional to depth for piles having shaft lengths not exceeding 10 base diameters. The results also show that there is no significant difference between the point resistance of piles in relatively homogeneous soils and piles founded in a bearing stratum overlain by soft, compressible soil at the same overall depth/base diameter ratio measured from ground surface. Values of the bearing capacity factor Nq were calculated by dividing the point resistance at failure by the effective overburden pressure at the level of the maximum cross section of the base. Nq was found to decrease dramatically with increasing effective overburden pressure, indicating that ambient stress level must be considered in bearing capacity analysis. The results show no evidence of a critical depth below which point resistance ...