Geologic effects of the high-explosive tests in the USGS Tunnel area, Nevada Test Site

Abstract

During the winter and spring of 1956-57 the U.S. Geological Survey ran a series of underground high-explosive tests at the Nevada Test Site. The purpose of these experiments, and of the subsequent relatively low yield Rainier nuclear blast, was to determine the feasibility of underground detonation as a method of testing atomic devices. In developing parameters for the effectiveness of various-sized explosions in rock, the following formula relating to depth of containment was used : where D= depth of cover, in feet Jc= constant W= weight of explosive in pounds. Although this formula has limitations, its use provides a good empirical basis for estimating the probable behavior of a given underground explosion. The USGS Tunnel consists of a main access-way 308 feet long and two lateral tunnels oriented at right angles to the main tunnel and terminated in explosion chambers, rooms A and B (10-ton and 50-ton explosion chambers, respectively). The workings were dug in tuffaceous pyroclastic rock of the Oak Spring formation of Tertiary age. This rock, which is rhyolitic to quartz latitic, consists chiefly of altered ash shards and pumice fragments but contains various phenocrysts of quartz, feldspar, and mafic minerals, and lithic inclusions. The rock is tunneled easily and generally stands well underground without support. Several small explosive charges of various sizes were fired in drill holes at various depths in the Oak Spring formation. These charges gave values for fr in the formula that ranged from 2.45 to 3.33. The 10-ton explosion was fired in room A on February 21, 1957, under 92 feet of minimum cover. A roughly oval area covering about 3.700 square feet was permanently raised 1 foot or more above its former position, and a subcircular area of nearly 12,000 square feet was lifted half a foot or more. Numerous fractures that were opened at the ground surface coincided chiefly with preexisting natural fractures. An instant after the shot was detonated, a horizontally directed blast of gas, dust, and rock emerged at high velocity from the portal of the tunnel. Underground, part of the wall of the explosion chamber had failed, permitting the gas generated by the explosion to bypass the stemming. The explosion chamber itself was greatly enlarged by the blast. The 50-ton explosion was fired in room B on April 5, 1957, under a minimum of 165 feet of cover. This explosion temporarily upclomed the ground surface above the chamber about 26 feet and permanently lifted it locally as much as 6 feet. The area strongly disturbed by the blast covers about 12,000 square yards and is roughly triangular in shape. Most of the strongest surface displacements were along preexisting fractures, but many surface fractures were formed within previously sound rock. Within 200 feet of ground zero the fracture pattern in previously sound rock was radial. Underground, the rock was severely fractured around the explosion chamber and the tunnel was closed by debris. Subsequently, entry to the chamber was reestablished, but most of the deb...

Detecting Surface Changes from an Underground Explosion in Granite Using Unmanned Aerial System Photogrammetry

“…While databases exist describing surface features associated with underground nuclear explosions (e.g., Garcia 1997;Grasso 2001;Cong et al 2007), details of the mapped features were constrained by the data capture method and the target of the mapping program. Previous studies have described morphological changes, such as fracturing and shifting of underground infrastructure, resulting from underground conventional explosions (e.g., Cattermole and Hansen 1962;Phang et al 1983;Yu et al 2014;Chowdhury and Wilt 2015), but have not described detailed changes at the ground surface or explored changes at the cm-to sub-cm scale. Similarly, while airborne and satellite remotely sensed methods have been employed to detect morphological changes and dynamic geological processes such as landslides, flooding, and coastal change (e.g., Gutierrez et al 2001;Glenn et al 2006;LePrince et al 2008;Niethammer et al 2010;Scaioni et al 2014;Pelletier and Orem 2014;Warrick et al 2016), the meter-scale data resolution range may overlook important, but smaller features.…”

Perched ground water in zeolitized-bedded tuff, Rainier Mesa and vicinity, Nevada test site, Nevada

“…Selected references are Cattermole and Hansen (1962), Hansen and others (1963), Diment andothers (1958a and1958b), McKeown and Dickey (1961), Dickey and Emerick (1961), , Emerick and Dickey (1962), and Laraway and Houser (1962).…”