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An analytical calculation is presented for the forced oscillations of bench foundations; results of comparison between experimental and computed data are described for Series K-lOOO foundations of IO00-MW turbinedriven sets, which suggest the possibility of practical use of the proposed method.The vibrational state of a turbine-driven-set/foundation/bed system is one of the basic factors determining the reliability of thermal and nuclear power plants. As the unit power of generating units increases, solution of the problem requires the development of methods for prediction of dynamic phenomena, especially for bench foundations. In that case, numerical methods encounter difficulties due to the large number of components and sudden changes in the parameters sought; analytical methods may, however, be found more preferable.Let us examine the forced oscillations of bench foundations in the vertical direction (Fig. 1). For the calculation, these foundations can, in first approximation, be represented in the form of a rectangular slab with walls-stiffeners (hereinafter called stiffeners), which are arranged at equal distances apart (Fig. 2). The stiffeners are calculated within the framework of the plane problem of the theory of elasticity, since their thickness is small in comparison to the length of the slab, which is sufficient for the stiffener to retain its stability. The effect of stiffener eccentricity relative to the median surface of the slab can be neglected, since this is essential only for a more precise definition of stresses in the plane of the slab. The slab is isotropic, and lies on a viscoelastic bed. The boundary conditions consist of a fixity, which permits vertical displacement, i.e., r-Ox=Wxxx =0 for x = +0,5LI; Wy=r~yyy=O for y = -+0,5L2.(1) A vertical concentrated dynamic load is applied at the center of the stiffeners along the longitudinal axis of the slab. Imagine the stiffeners to be separated from the slab, and the effect of the i-th stiffener on the slab replaced by the contact force u(x, z, t). The simplified homogeneous differential equation of the plane theory of elasticity [1] ~u a~u . ~u s--Z+o-AT-; = 0,

The paper provides a quantitative assessment of the deflected mode of foundation stratum of finite width foundation, in the compressible thickness of which there is a slack clay soil layer. A number of criteria for assessing the possibility or impossibility of extruding a slack layer depending on its strength and rheological properties, as well as the relative thickness of the layer to its length (h/l) and the relative depth of the layer (h/d) have been given. Closed analytical solutions are given to determine the rate of Foundation precipitation depending on the rate of extrusion of the weak layer, including taking into account the damped and undamped creep.

The paper provides a quantitative assessment of the deflected mode of foundation stratum of finite width foundation, in the compressible thickness of which there is a slack clay soil layer. A number of criteria for assessing the possibility or impossibility of extruding a slack layer depending on its strength and rheological properties, as well as the relative thickness of the layer to its length (h/l) and the relative depth of the layer (h/d) have been given. Closed analytical solutions are given to determine the rate of Foundation precipitation depending on the rate of extrusion of the weak layer, including taking into account the damped and undamped creep. The analytical solutions in the article are supported by the graphical part made with the help of the Mathcad program. Plots of changes in shear stresses in the layer along the x axis at different distances from the axis and at different values 0, contours of horizontal displacement velocities in the weak layer at different distances from the x axis, plots of horizontal displacement velocities in the middle of the weak layer and plots of horizontal displacement velocities in the weak layer at different distances from the x axis are given. As a calculation model for describing the creep of a slack layer, rheological ones of the soil using power and hyperbolic functions and their modifications have been considered. In addition, most modern rheological models that take into account soil hardening during creep have been considered. Based on these models, the problem is solved by means analytical and numerical methods using the Mathcad PC and the PLAXIS PC according to the Soft Soil Creep model. The graphical part shows the isofields of horizontal displacements for 300 days and 600 days and the corresponding contours of horizontal displacements.