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In [i, 2], the propagation of pulses and vibrations in elastic media of plecewise-homogeneous structure was considered, using one-dimenslonal wave equations to describe the motion of structural elements. A series of features which are present in nonsteady processes in composite systems of regular structure end disappear in the equivalent homogeneous models of the long-wave approximation have been discovered.One-dlmenslonal models, as used in [i, 2], are suitable for the description of the dynamic state of the medium under the action of real perturbation sources of special form, for which the direct wave can be regarded as plane.Below, the wavegulde properties of a medium of block structure is analyzed on the basis of a two-dimensional model (plane formulation): the blocks --rigid bodies of rectangular cross section --interact through intervening elastic layers. In the case of antiplane deformation, an analogous structure was considered in [3], where the steady problem of semiinfinlte-crack motion in the layer between blocks was investigated.

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