Static Loading Of Small Buried Arches
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Static Loading of Small Buried Arches
Static and dynamic tests have been performed to study the behavior of small buried arches. The objective was to gain information which will serve as a guide in developing design methods for underground structures. This report describes the static tests, the prime purposes of which were: (1) to obtain information on the behavior of a statically loaded soil-arch system, and (2) to provide data for comparison with that from a similar system subjected to blast loading. The test configuration consisted of two conterminous semicircular arches each 30 inches in diameter buried in dry sand with 6 inches of cover over the crown. The arches were identical except for differing footing widths. The entire system was contained by the NCEL atomic blast simulator pit, which is 9 feet by 10 feet in plan and 12 feet deep. Static loads up to 25 psi were applied to the surface of the sand as various measurements were being made. The test results show that the expected decrease in footing deflection with increase in footing width was accompanied by an increase of maximum moment in the arch. (Author).
Blast Loading of Small Buried Arches
It was evident that the passive pressures which developed on the sides played the dominant role in providing resistance. It has been found that in static tests some of the surface load is carried by arching through the soil. In the dynamic tests the inertial forces of the soil above the arch were found to be important. The inertial load overcame the soil shear resistance so that a load approximately equal to the surface load acted on the structure. A model analysis of the system and subsequent comparison of the deflections from the small-structure tests and the Operation Plumbbob Structure 3.3 tests indicate that modeling of deflections is possible.
Static and Blast Loading of Small Buried Cylinders
This research was performed to obtain information on the behavior of shallow-buried cylinders subjected to static and blast loads in support of the task objective of gaining knowledge to provide guidelines for developing design methods for underground protective structures. It was especially desired to obtain data on the time and space variations of deflection, thrust, and moment under the two types of loading for purposes of making a comparison. The results show that the net arching across a flexible shallow-buried cylinder is small and that the maximum moment occurs at the bottom of the cylinder. Differences in response to static and blast loading are relatively small except for the crown, which deflects about twice as much under blast loading as under corresponding static loading. An analogy with the simple spring-mass system is drawn to explain this behavior. Information obtained on the influence of placing a low- strength isolating material in the soil over a cylinder indicates that such an expedient is of questionable benefit.