It has been ascertained from experimental investigations conducted in recent years that the use of computational schemes --the traditional model of the soil medium --does not reflect the characteristics of the limiting behavior of a soil in engineering computations of the foundations of earth structures.For example, the "loading history," i.e., the duration of the loads applied to the soil, assumes an extremely critical significance, which affects the development of soil deformations.It is precisely this fact, however, that is completely ignored by applied theories --deformation-type theories.The need to construct those schemes (models) that can account more fully for known behavioral characteristics of soils and, e.g., the loading history, has arisen in this connection.A model, within the framework of which this can be done --the theory of plastic consolidation, which is employed to describe the limiting behavior of a soil --was proposed and developed in [1][2][3][4][5]. The latest advancement in this type of theory is cited below.The following assumptions are made in the theory of plastic consolidation.i. The total-strain tensor is represented as the sum of the plastic and reversible components ~,~=~,j+~,~,where EPij is the plastic component of the strain tensor and eeij is its elastic component.2. The existence of a loading surface [4][5][6][7], i.e., a surface li, which separates the region of irreversible strains Dee from the region of elastoplastic strains D C by a strip in the space occupied by the principal stresses, is assumed.3. The vector of the plastic-deformation increase is directed normal to the loading surface, i.e., the effect of Drukker's postulate under conditions of a quasiequilibrium process is observed [6, 7]. The convexity of the loading surface ~i in the direction of the elastoplastic region D C follows from Drukker's postulate.Moreover, the theory assumes the hypothesis that under conditions of a quasiequilibrium loading process, the surface E i is regular in the limiting region, i.e., the normal for any point on the loading surface is determined by a single method.Let us assume that the loading function is dependent on the following arguments:where aij is a stress tensor, W is the moisture content of the soil, and T is the absolute temperature.The loading surface is given by the expression f-~ (=zi, ~%, ~r T)=0.(2)*The results described are based on systematic studies of the mechanical behavior of certain soils, which were conducted in the soil mechanics, beds, and foundations department of the V. V. Kuibyshev
