Hello battal4468, Are you sure about the change in the Shelter Regulation?
b) Thickness of building exterior wall surrounding the shelter : The thickness of the walls and ceiling covering the outside of the shelter should be at least 60cm concrete, 75cm brick or stone or 90cm compacted soil. It can be used alone or together by considering the ratio of these measures to each other in terms of radiation transmittance.In addition, different building materials can be used together or alone by calculating their measurements by taking into account the permeability and protection coefficients against radioactive fallout.The shelter is completely under the ground. The thickness of the remaining outer walls, which have at least 60 cm soil filling between the outside and the open environment, is determined according to static calculations. The same practice is applied in the shelters to be built. Link:
What is the basis of the control mechanism that asks you to lay 60 cm in the building? I would appreciate it if you share it... good work, regards...