Mine Throw was a series of tests conducted by the Defense Nuclear Agency using conventional charges to simulate the blast effects of nuclear weapons. This series is somewhat poorly attested.
DNA continued its pursuit for the utilization of ANFO for ground shock simulation through contractors and others better versed in underground shock phenomena than NSWC. F. Sauer, PI (Physics International Company) had a novel technique for simulating crater and direct induced ground motions from a nuclear weapon surface burst. This technique, with the acronym CHEST (Cratering High Explosive Simulation Technique), is based on the following, assumption: if the velocity field from a source of chemical energy can be made identical' to the late stage velocity field from a nuclear source, then the ensuing cratering and far field ground motions will be identical also. The velocity fields can be made identical if a chemical energy source can be made to generate the same boundary conditions on a region of space that would be generated by a nuclear surface burst. ANFO was chosen as the explosive to be used because it could meet the required boundary conditions i.e., the work stresses in the test site soil, and because it was easy to emplace and its cost was low.
In pre MINE THROW tests in 1970-1971, the technique was tried out on a small scale. In one test for instance, a hole approximately 9.6 ft in diameter and 6A ft in depth was dug. This excavation was lined with a 2 ft thickness of ANFO contained in 10 lb bags and totaling about 6 tons. The excavation size and ANFO quantity were selected on the basis of two dimensional computer (ELK) calculations which provided contours of constant peak stress; for the purpose of the experiment, the 55 kilobar stress, contour was selected as the one of interest since it was expected that ANFO would generate approximately that pressure when reflecting off the alluvium interface. The preliminary tests showed the feasibility of CHEST but it also indicated some problems. The detonation pressure was considerably higher than expected; the measured pressures were on the order of 90 to 100 kilobars.
Nine special charges of high explosive (pre-Mine Throw IV), ranging in size from 256 lb to 102 tons, were detonated under controlled conditions in the lake bed playa of the Nevada Test Site to study the yield-scaling of cratering-induced ground motion waveforms. Cratering-induced motions are surface motions, observed out of approximately four crater radii, which result from the dynamic aspects of crater formation.
One 256 lb and one 1000 lb half-buried sphere, three 1000 lb above-the-surface tangent spheres, a 7.1 ton tangent sphere and a 102 ton tangent sphere were instrumented at eight radii along three lines spaced 120 degrees apart to measure the horizontal and vertical components of particle velocity. For the 256 lb and 1000 lb charges, instrumentation having a 2000 Hz upper frequency band edge was used; for the larger charges the gage frequency response was approximately one-tenth this value.
Comparison of the cratering induced portions of the ground motion waveforms from the small and large yield events show that the lengths scale as W 1/n, time scales as W 1/nt and particle velocities scale as W 1/mv, where W is explosive yield. These results imply that the cratering motions are gravity controlled which is in agreement with recent work on hypervelocity impact crater growth in sand done at the NASA Ames Research Center. The influence of secondary airblast peaks in altering the scaling of cratering-induced is also illustrated by the Pre-Mine Throw IV results.
The successful deployment of an MX missile system would require a careful consideration of ground shock effects which were of secondary importance in previous applications. For example, with the system sited in a valley and under a multiple attack scenario, untargeted points can be expected to experience a significant ground motion environment as a result of the superposition of motions originating from attacks on a variety of surrounding aimpoints. Furthermore, reflections of outgoing energy from the valley boundaries can be expected to complicate the ground motion environment within the valley, particularly at late times. The objective of this work was to develop a better quantitative understanding of these late time, long period ground motions in order to provide a firmer basis for scaling to new geologic conditions. Particular emphasis was placed on the identification of the characteristic mode of propagation associated with these arrivals.
A theoretical model was used to compute the surface waves produced by a propagating airblast load acting on the surface of a multilayered, elastic half-space. This model was then applied to the analyses of both the observed data and finite difference simulations of the Pre-Mine Throw and Pre-Dice Throw 100 ton HE surface blasts.
One source states that the August 1974, 100-Ton event named PRE-MINE THROW IV was conducted at the Atomic Energy Commission's (AEC) Nevada Test Site, located about 90 miles north of Las Vegas. The Event was nearly identical to DIAL PACK and MIXED COMPANY. The explosive charge was different in that this time it was only 100-Tons and it was liquid Ammonium Nitrate/Fuel Oil [ANFO] explosive in a cylindrical container. However, the authoritative history of the early use of ANFO makes no mention of this test, and discusses the Pre Dice Throw series as having introduced ANFO into common use.
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