The block element method is used to investigate the behavior of the coated material under the assumption that the surface is exposed to an active liquid medium capable of destroying the coating, including in the process of subduction, tsunami preparation, landslide processes. It is assumed that the destruction begins with the formation of vertical local cracks in the coating, which then grow and lead to the exposure of the unprotected surface. Assuming the possibility of modeling a liquid layer by shallow water equations, we investigate a block structure that includes a body in the form of a deformable layer, a defective coating modeled by Kirchhoff plates and a heavy liquid layer. The distribution of the stress concentration in such a block structure is studied and the conditions both allowing the further use of such an object and excluding this possibility are revealed.