Research For Cave Overlay Thickness Base On Underground Explosion Similarity Law

At present,the overlay thickness design of countries underground arsenals relies too much on experience,so it's difficult to obtain reasonable overlay thickness.The overlay thickness determined by full size model test is too costly and it is uneasy to success.There are no clear answer about the problem of whether we can determine the overlay thickness through low-cost small model tests.Based on the underground explosion cave damage model test,the question was researched in this paper by means of similarity theory and numerical simulation and research achievements have been obtained in the following.(1)Established and verificated the similarity law about underground explosion cave cover vibration and defined the similarity law as follow:the explosion in caves,when keep the same explosive type,rock material,boundary conditions and the ratio among explosives,cavern and overlay unchanged,then the peak vibration velocity of the same position in overlay remains the same,the product of the peak vibration acceleration value and the explosive weight cube root unchanged.(2)Corrected the Sadauskas empiric formula in allusion to its deviation to get a modified formula and make it more suitable for ascertaining underground explosion cave overlay damage.(3)Based on the test results,to obtain the critical overlay thickness of the cave model by the modified Sadauskas empiric formula and acquire the cave model damage range according to the Sadauskas empiric formula.The modified formula was verificated more reliable by mean of comparing with the results of ultrasonic detection test.(4)Based on the underground explosion cave cover vibration similarity law and the modified Sadauskas empiric formula to determine the prototype cave overlay thickness on the basis of the caves safety coefficient at 2 in combination with the physical model test results.Comparing with the overlay thickness determined by the current specification at the same conditions and the comparison result showed that the cave layer thickness determined by the paper was more reasonable and then validated it is feasible to determine underground arsenals cave cover thickness through small model test.