20-TON AND 1/2-TON HIGH EXPLOSIVE CRATERING EXPERIMENTS IN BASALT ROCK. Final Report, August 1962
5 7 : 7 5 ; 6 9 = 6 < ; 5 8< : < = < 8 9 : 8 6 : TNT and blocks of cast TNT stacked to resemble 40,000-pound spheres were center detonated. The 1,000-pound charges were burst, two each, at depths of 5, 10, 15, 20, and 25 feet. The 40,000-pound charges were buried at depths of 25.7, 42.75, and 59.85 feet to the charge center. One 1,000- pound charge, placed at 25 feet, was a cylinder with a length-todiameter ratio of two. It was placed with the long axis vertical. This charge was detonated to determine if there were detectable differences in crater dimensions attributable to charge shape. The basalt rock had a density greater than 2.6 gm/cm/sup 3/ and a compressive strength close to or above 20,000 pounds per square inch. The first 12 to 15 feet of basalt was usually highly vesiculated, and hence in this region density and compressive strength were less than the values listed above. The scatter in crater dimensions made it impossible to determine whether or not departures from cube-root scaling existed. Ground surface displacement as a function of time was determined from motion picture photography. Contributions of both the ground shock wave and the motion induced by pressures of the explosion gases were clearly distinguishable. Empirical relationships for peak shock-induced velocity in basalt are compared with comparable results from shots in desent alluvium and in tuff. Shock-induced ventical acceleration and gas- pressure-induced acceleration are also compared with similar results from 40,000- pound charges in alluvium. Fine particulate or dust ejected by the explosion was collected at eight distances along 12 radii. An empirical relationship was developed for giving the mass of fine particulate as a function of the volume of the apparent crater. The mass of fall-back coming from a Buckboard explosion compares within a factor of two with the mass of fall-back from comparable Stagecoach detonations. Measurements of ground motion and pressure were attempted on Shot 12. Measurements tried included acceleration, velocity, stress, and strain along a horizontal radius at the burial depth of the charge. Information was obtained from ten of twenty-two attempted measurements. In the remaining channels there were either serious system failures before signal arrival or else set ranges were much too high for the weak signals transmitted. Measured and calculated values of peak stress differ by a factor of two. If the difference can be attributed to a discrepancy in calibration constants, then the data obtained from surface velocity and from stress measurements are consistent. Vertical displacements of the dust clouds, including earth mound, smoke crown, column, and jetting material, were determined from motion picture photography. Horizontal dimensions of the base surge, cloud, column, and the jets were also determined. Vertical velocity as a function of time was obtained from the displacements. These observations were limited to the 40,000-pound charges. The two shallower shots show a definite contribution to the sustainment of the velocity by the emergence of jetting material. Venting times, compared with those in alluvium and tuff, are presented in the form of relationships for burst depth as a function of venting time. Plots of the log of scaled burst depth against scaled time of jet breakthrough show a linear relationship for both basalt and alluvium, with different slopes but with the same intercept at zero time. There was no well defined column on the deepest Buckboard shot. At corresponding times, the column heights in basalt are greater than those in alluvium. Differences in the growth of the base surge to the left and right of the camera line-of-sight on Shot 12 cannot be attributed to winds because of low velocities existing at shot time. The most rapid growth occurred on the side of the crater which was excavated in solid basalt; the other half was in cinders. Close-in air blast was measured along
- Research Organization:
- Albuquerque, N. Mex.
- DOE Contract Number:
- %AT(29-1)-789<
- NSA Number:
- NSA-17-001168
- OSTI ID:
- 4777697
- Report Number(s):
- SC-4675(RR)
- Resource Relation:
- Other Information: PROJECT BUCKBOARD. Orig. Receipt Date: 31-DEC-63
- Country of Publication:
- United States
- Language:
- English
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