Bearing Capacity of Concrete Blocks or Rock

The limit theorems of the generalized theory of perfect plasticity are applied to obtain bearing capacity in two dimensions (strip loading or rigid punch) and in three dimensions (circular and square punches). With the safe assumption that concrete or rock is unable to take any tension, the bearing capacity is shown to be just the unconfined compressive strength of the column of material directly under the load. When a small but significant tensile strength is assumed, along with the Mohr-Coulomb surface for failure in compression taken to represent a perfectly plastic yield surface, the predicted capacity is found to be in good agreement with published test results. The influence of friction in this class of problems is also analyzed as is the limited applicability of so drastic an idealization of the real behavior of a material as brittle as concrete or rock.