High-speed Photography Studies of Laboratory Cratering in Tennessee Marble Plates.
Condon JL; D'andrea DV
NTIS: PB 209 010 :18 pages
High-speed movies were taken of crater experiments in two- dimensional plates of Tennessee marble to study craters being formed primarily by stress-wave action. The contribution of gas action to the cratering process was minimized because the two-dimensional models did not contain the expanding gases from the explosive. Four burdens were studied for solid plates and one burden for a segmented plate. After cratering, the plates were reassembled for dye penetrant studies of the fracturing. Flyrock velocities were calculated and related to the degree of fracturing, and compared with those from quarry shots. In general, the smallest burdens produced the highest flyrock velocities and the least amount of fracturing. Flyrock velocities compared favorably with initial flyrock velocities in quarry blasts, but did not show step accelerations owing to gas effects as did the quarry blasts. The test with a segmented plate was used to simulate cratering in a jointed material and showed that stress-wave effects can be important for crater formation in jointed rocks.
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