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The purpose of the study of engineering properties of nuclear craters is to identify and describe the physical properties that will control the use of a nuclear crater for engineering purposes. One of the prime considerations in the engineering use of a nuclear crater is the stability of the crater slopes. The late time mechanism of explosion crater formation is a deposition phenomenon. The inclination of a slope formed by deposition of cohesionless material is termed the angle of deposition, and the maximum possible inclination of the slope is termed the angle of repose. This definition differs from some common definitions of angle of repose. The factor of safety of a slope formed by deposition is defined as the ratio of the tangent of the angle of repose to the tangent of the angle of deposition. Variations are recognized in the angle of deposition with the manner of deposition, and in the angle of repose with varying relative density and particle orientation. Such factors as particle size, shape, and angularity, structure of particle aggregations, manner of deposition, and geometry of slopes are discussed with regard to their relative influence on each of the aforementioned angles. A few simple analytical relations are given to aid in understanding the behavior of particles during deposition and their stability on an inclined surface. Empirical data from laboratory tests, stockpiles, rock-fill dams, natural slopes, explosion-produced craters, etc., are presented and compared. (Author).
Analogies between nuclear and conventional excavations are developed from a tabulation of data from 153 mine, quarry, roadway, and dam excavations. The following factors were used as the basis for tabulation of conventional excavation data: purpose, location, precipitation, temperature, ground water level, lithology, mass strength, structural pattern, slope plan, slope profile, depth of excavation, slope height, average inclination, and stability. It was found that average slope inclination tends to be greatest for hard material and for material lacking a well-developed structure, and that inclination tends to decrease with increasing slope height for excavated slopes reported to be stable. The authors conclude that good analogies are to be found in shape, slope height, depth of excavation, and slope inclination. (Author).
Investigations were conducted to select a site suitable for producing craters in a saturated cohesive medium by small-scale high-energy detonations. According to prescribed criteria, the ideal site would be a large (200 acres or more), cleared, moderately flat tract of Federally owned land characterized by soft, homogeneous clays to a minimum depth of 40 feet. An evaluation of the U.S. by physical divisions revealed that suitable sites might occur in four general areas, i.e. (1) the Lake Bonneville area, (2) the Lake Agassiz area, (3) the Great Lakes area, and (4) the Lower Mississippi Valley area. Acquisition and analyses of pertinent data on these areas indicated a need for field reconnaissances except in the case of the Great Lakes area which was eliminated from further consideration because of heterogeneous soil deposits. A reconnaissance of the Lake Bonneville area indicated the presence of apparently favorable test site conditions in a portion of the Dugway Proving Ground, Utah. The Dugway site was concluded to be the most suitable for the project. (Author).
The third phase of the overall project is devoted to study of cratering phenomena in three specific situations that are of particular interest in engineering practice, namely: (1) the situation where the cratered medium is submerged under the water table; (2) the situation where the surface of the cratered medium is sloped; (3) the situation where several explosive charges are set off simultaneously in a medium. Thus, Chapter I is devoted to the experimental study of cratering phenomena in saturated or submerged media. Chapter II describes the experiments in which pore-fluid stress waves caused by an explosion in a mass of submerged, dense sand were measured and discussed, with particular emphasis on possible residual pore-fluid stresses. Chapter III is devoted to the problem of craters formed by explosions close to the sloped surface of a semi-infinite medium. Chapter IV deals with cratering phenomena caused by multiple charges, where coalescence of cavities may occur following detonation. (Author).