The article is devoted to the development of a scientific and methodological apparatus that allows during reconstruction to make verification calculations of a special fortification in non-rock soils for the impact of seismic waves of a nuclear explosion, taking into account the actual state of the load-bearing structures. In particular, in this article, the authors proposed and consecrated a method for calculating reconstructed excavation special fortifications in non-rock soils on the impact of seismic waves of a nuclear explosion, taking into account the actual state of the load-bearing structures. The theoretical significance of the described technique is to substantiate the application of the theories of continuum mechanics, elasticity and plasticity, and methods of finite elements and initial stresses in the calculation of load-bearing structures of special excavation fortifications to the effects of seismic waves of a nuclear explosion during the design of the reconstruction of the KSFS. The practical significance of the methodology developed by the authors lies in the possibility of application to assess the actual condition of the bearing structures of the excavated special fortifications after exposure to dynamic loads.