Centrifuge Crater Scaling Experiment II. Material Strength Effects
Interim rept. 31 Jan 78-31 Jan 79
BOEING AEROSPACE CO SEATTLE WA
Pagination or Media Count:
Direct simulation of large-scale explosive events can be performed at subscale using the elevated gravity field of a centrifuge. This technique allows prediction of different soil-media effects in a well-controlled manner over many orders of magnitude in explosive energy. Cratering experiments were conducted in desert alluvium, dry Ottawa sand, saturated sand, and an oil-base clay. Both lead-azide and pentaerythritol-tetra-nitrate PETN explosives were used. These various experiments incorporated large differences in explosive specific energy, soil cohension, soil angle of internal friction, charge weight and gravitational acceleration. Experimental results show substantial differences in cratering phenomena. At small actual yields soil cohesion dominates the cratering process. At larger yields, the cohension has little effect, but the angle of internal friction becomes an important variable because of the large overburden. The behavoir of a material such as alluvium, having nonzero values for both cohension and internal friction, shows cube-root scaling at low yields but becomes asymptotic to dry sand behavior at large yields. Neither behaves as a zero-strength material, and neither shows quarter-root scaling for scaled yields approaching megatons of TNT.
- Soil Mechanics
- Test Facilities, Equipment and Methods