There is an unquestionable need for using theoretically substantiated and experimentally checked methods for determining the thickness of film elements when designing watertight polymer-film cutoffs. More than I0 years ago I. E. Krichevskil proposed an empirical formula for calculating the thickness of film diaphragms [1]. This formula in a slightly modified form became a part of standard VSN 003-66 of the Ministry of Power and Electrification of the USSR (Minenergo). Subsequently, on the basis of an analysis of a large body of experimental data, Krichevskii's formula was refined by V. P. Lysenko and was included in VSN 07-74 of Minfnergo.* The formulais basedon the assumption that on a soil foundation the film behaves as a membrane of elastic material with a circular undeformable contour. The given formula did not make it possible to take into consideration a number of stressed states characteristic for the loading conditions of a film diaphragm. To some extent this consideration could be accomplished by means of the formulas proposed by A. A. Mironov for slumpprone and fractured foundations. However, Mironov's empirical relations are based on vague concepts about the behavior of the film material and do not cover many types of stressed states.