Measurements and visual observations made during the Hardtack II series of underground shots provide basis for conclusions regarding shock-resistant design of protection for cavities in rock and qualitative prediction of permanent displacements in rock due to nuclear detonations. Vibration measurements on blast-resistant construction in soil provided non-nuclear test results which apply to shock resistant design. With varying soil cover, the compressive mode predominated in arch structures and a mass of soil apparently acted with the structure that varied in magnitude in inverse fashion with two depths of cover. Underground structural harmonic response theories were in part verified, for some structures, though the absence of an appreciable flexural mode in buried arch structures was significant.