The results of a number of laboratory model tests for the short-term u
ltimate uplift capacity of a circular plate anchor embedded in saturat
ed soft kaolinite and montmorillonite are presented. The tests were co
nducted with and without venting the bottom of the plate anchor in ord
er to determine the variation of the suction force with embedment rati
o. The variation of the suction force is presented in terms of the und
rained shear strength of the clay and also the net ultimate uplift cap
acity.