Experimental Study of Buckling of Buried Domes

Experimental study of restraint provided by the sand to burled domes is discussed. Under hydrostatic pressure unsupported (free) domes undergo premature bucking at loads below the theoretical level, as a result of local disturbances. With improving production, the buckling load approaches the theoretical one. When the local buckling is arrested, the corresponding state of equilibrium is skipped, and the dome progresses towards the theoretical buckling as the load increases. Tests on buried domes showed that the sand plays a role only insofar as it serves as the load-transmitting medium. While the domes underwent ordinary premature buckling under water head, they proved capable of bearing higher loads when transmitted through the sand. When the whole load is transmitted through the sand, three ranges of failure were observed: premature buckling under a thin cover, near-theoretical buckling under a medium cover, and yielding under a thick cover. Transition between the ranges was abrupt, and produced arching over a site of local buckling, thereby equilibrating the membrane forces and tiding the dome over to a higher buckling mode.