Uplift Resistance of Cohesive Soils

Effects of vertical uplift forces on circular anchors in purely cohesive soils are considered. Model tests indicate a general type of ultimate uplift failure in shallow anchors, occurring by yielding above and below the anchor due to shear and tensile stresses and cracking in the soil. Existing shallow anchor theories, although in substantial agreement with one another, overestimate actual ultimate uplift resistance since they do not take into account tensile stresses and cracking. Model tests indicate a local type of failure in deep anchors and confirm existing deep anchor theories that take account of soil compressibility. Dimensional analysis indicates that caution must be exercised when interpreting model uplift test results in terms of the prototype, particularly when the prototype soil has low shear strength. A finite element program has been developed to estimate, within limitations, the magnitude and direction of stresses occurring in each element of the mesh at any stage of uplift resistance.