e In this case rigid medels could be used, If models are to be omploycd as a measure ofstructural behavior certain factors such as gravitietional leacs do not sealo and means must be established for componsating for these variations from scaled behavior, The results of the tests emphasised the fret that aoduels at Less than one-quarter sealo arc impractical and aiso tnat models of very smell size are of doubtful use because of the eficct of irregularitics of the sround on the blast wave, ~lp3 “eS tits AT DALE ® aS Toe . eae cl Fas Bids eiidi of it wh et a, aha* J. fof EY