EFFECTS OF BOUNDARY FRICTION ON TRANSMISSION OF STATIC STRESS THROUGH AND IN CYLINDRICAL TANKS.
Technical rept. for Sep 63-Feb 64,
NEW MEXICO UNIV ALBUQUERQUE AIR FORCE SHOCK TUBE FACILITY
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Experiments to determine the effects of boundary friction on the transmission of static vertical stress through standard 20-30 Ottawa sand in 8-inch I. D. tanks are discussed. In these experiments the tank type, tank height, applied overpressure, sand density, and boundary treatment were varied. Theory and derived values for the coefficient of wall friction are included. Tests showed that the transmission did not vary significantly with overpressure between 12 and 6 kgsq cm 7.11 and 85.32 psi, but decreased as the height of the tank increased. The decrease in transmission with increase in tank height could be approximated by the theoretical equation up to some maximum height. It is concluded that a greased membrane is perhaps the simplest and certainly an adequate means of reducing wall friction to such levels that no correction in the free-field average vertical stress over small areas in the center of the tank should be required. This could be said of a tank with a height even as great as three times its diameter. Author