Responses of four rock mediums to contained nuclear explosions

Abstract

Underground nuclear tests in tuff, alluvium, rock salt, and granite have yielded data essential to the evaluation of the effects of contained nuclear detonations. The data indicate that for these mediums the cavity radius is predictable within ñ20 per cent without regard to the physical or chemical properties of the rock in the immediate shot environment. Properties of the chimney of broken rock resulting from collapse of the cavity, on the other hand, are found to be related to the physical properties of the rock and to preshot structural weaknesses within the rock. Introduction. Recent underground nuclear tests conducted by the U.S. Atomic Energy Commission have yielded data on the effects of contained nuclear explosions in four rock mediums: tuff, alluvium, rock salt, and granite. This report presents and compares data. obtained primarily through exploratory mining and drilling into the postshot environments of 35 such events.With one exception, these events were either weapons development or military effects tests. Only five were explored in detail for the purpose of defining the environment after the shot; the remainder were usually explored after the shot with two or three drilled holes. As a result, the data are not as complete as would be desirable. However, comparison of the available data does provide a measure of the sensitivity of explosion-produc'ed effects to the properties and structures of the containing rock medium.The phenomena considered in this report are (1) the cavity created by the expansion of the explosion-produced gases, (2) the chimney of broken rock resulting from collapse of the cavity, and (3) the zone of fractured rock immediately beyond the chimney.Cavities. The sizes and shapes of cavities produced by contained nuclear explosions were inferred primarily from drilling data obta.ined in the region below the shot point. It was impossible to measure the roof of the cavity above the shot point because in all cases the original cavity produced by the explosion collapsed within seconds to hours after detonation of the device.

The apparent explosion moment: Inferences of volumetric moment due to source medium damage by underground nuclear explosions

“…Furthermore, it was too much to ask the data set of ∼80 Pahute Mesa shots to resolve the effects of material strength, measured by shear velocity β , from the effects of overburden P 0 ( ρgh , where g is gravitational acceleration). Thus we adopted quarter‐root scaling on P 0 , as Boardman et al [1964] did, which is not very different from the scaling exponent (0.2625) determined by DJ91 from a much larger data set. The parameterization used in our study is where C and x are unknown constants to be determined by the observations.…”

Seismic radiation from explosions in prestressed media and the measurement of tectonic stress in the Earth

“…Use of this model entails the specification of another source parameter Re. We can, however, obtain an independent estimate of Rc from the results given by Boardman et al [1964]. of the estimate on Re, and the only significant differences in the possible curves occur at high stress and low Ro values.…”

The Potential of Plowshare for Resource Development

“…Assuming that the cavity is formed by adiabatic expansion of high-pressure gas to overburden pressure, cavity radii can be calculated by using the approximate relation (Boardman et al, 1964): Assuming that the cavity is formed by adiabatic expansion of high-pressure gas to overburden pressure, cavity radii can be calculated by using the approximate relation (Boardman et al, 1964):…”