Abstract
An investigation was made on the ultimate bearing capacity of deep circular foundations in undrained saturated clay, theoretically and experimentally.
The slip-line fields around two-dimensional model foundations with various kinds of cross sections under vertical loading were observed. When there was movable space of the soil mass between the-foundation side and the ground, like foundations constructed on the bottom of a slope and cones penetrating into the ground, etc., the slip-line fields were found to be the ones in which slip-lines reached the foundation side as Meyerhof had assumed.
However, when there was no movable space of soil mass, like deep foundations and piles, the slipline fields were done to be the one in which slip-lines reached still the ground surface different from Meyerhof's assumption.
The slip-line fields around circular deep foundations in clay were analyzed three-dimensionally under the condition of axi-symmetry, using the observation results and the slip-line fields with the intermediate transient region used for calculating the earth pressure of a broken-back retaining wall by Sokolovsky. The analysis was made under the assumption that the soil was perfectly plastic-rigid and stress fields was satisfied Haar-von Karman's condition.
The results of analysis were expressed as the bearing capacity factors (Nc) in terms of the ratio of depth/width of foundations (Dp/2 R). The in-situ test results obtained earlier were found to agree well with the theoretical bearing capacity factors.
