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This report will discuss the distinct element method (DEM) with particular emphasis on techniques for achieving improved computational efficiency, including the handling of contact detection and approaches to parallelization. Some...
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This report will discuss the distinct element method (DEM) with particular emphasis on techniques for achieving improved computational efficiency, including the handling of contact detection and approaches to parallelization. Some continuum approaches to the simulation of underground facilities are discussed along with results from underground explosions. Finally, our DEM code is used to simulate dynamic loading of several generic subterranean facilities in hard rock for a range of joint properties and sources, demonstrating the suitability of the DEM for this application.
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Underground space is a great, unspoiled frontier whose orderly development is essential to the well-being of our nation. The need for planned,coordinated development of underground space is immediate. The key element in exploitati...
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Underground space is a great, unspoiled frontier whose orderly development is essential to the well-being of our nation. The need for planned,coordinated development of underground space is immediate. The key element in exploitation of the subsurface lies in substantially reducing the cost and in improving the methods for underground work. For this purpose the Interagency Committee on Excavation Technology (ICET) was established to coordinate and optimize Federal investment in excavation research and technology. This report provides a summary of the activities and progress made by the committee since publication of an initial report in April 1972.
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The characteristics of fractures in unit 2 of the Tshirege Member of the Bandelier Tuff were documented in Pit 39, a newly excavated 13.7 m deep disposal pit at Material Disposal Area G on Mesita del Buey. The average spacing betw...
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The characteristics of fractures in unit 2 of the Tshirege Member of the Bandelier Tuff were documented in Pit 39, a newly excavated 13.7 m deep disposal pit at Material Disposal Area G on Mesita del Buey. The average spacing between fractures is about 1.0 to 1.3 m, the average fracture aperture is about 3 to 5 mm, and the average fracture dip is about 76o to 77o. Fracture spacing and dip in Pit 39 are generally consistent with that reported from other fracture studies on the Pajarito Plateau, although the fracture apertures in Pit 39 are less than reported elsewhere. Measured fracture orientations are strongly affected by biases imparted by the orientations of the pit walls, which, combined with a small data set, make identification of potential preferred orientations dlfflcult. The most prominent fracture orientations observed in Pit 39, about E-W and N20E, are often not well represented elsewhere on the Pajarito Plateau. Fracture fills contain smectite to about 3 m depth, and calcite and opal may occur at all depths, principally associated with roots or root fossils (rhizoliths). Roots of pifion pine extend in fractures to the bottom of the pit along the north side, perhaps indicating a zone of preferred infiltration of water. Finely powdered tuff with clay-sized particles occurs within a number of fractures and may record abrasive disaggregation associated with small amounts of displacement on minor local faults.
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The objective of this program was to evaluate a number of roof support systems that have some physical similarity to the truss introduced by the Birmingham Bolt Co. in 1966. The report is in two parts: Part I is a state-of-the-art...
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The objective of this program was to evaluate a number of roof support systems that have some physical similarity to the truss introduced by the Birmingham Bolt Co. in 1966. The report is in two parts: Part I is a state-of-the-art study of roof truss technology as of January 1979. Included are a history of the truss concept, a review of analysis techniques, a record of hardware available and equipment used in its installation, and examples of user experience. Part II is concerned with a study of the role of friction in the behavior of a roof truss.
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There exists a need to develop a method to locate underground voids, or caches. In the past, ground penetrating radar (GPR) operating in the time domain mode has been used. In this paper, we turn our attention to stepped frequency...
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There exists a need to develop a method to locate underground voids, or caches. In the past, ground penetrating radar (GPR) operating in the time domain mode has been used. In this paper, we turn our attention to stepped frequency radar, capable of making frequency domain reflection coefficient measurements. We then apply the inverse Chirp-Z transform (ICZT) to this data, generating a time domain response. The scenario under consideration is that of an airborne radar passing over the surface of the earth. The radar is directed toward the surface and is capable of measuring the reflection coefficient, seen looking toward the earth, as a function of frequency. The frequency domain -data in this work is simulated and is generated from a transmission line model of the problem. Using the ICZT we convert this frequency domain data to the time domain. Once in the time domain, reflections due to discontinuities appear at times indicating their relative distance from the source. The discontinuities occurring beyond the surface of the earth could be indicative of underground structures. The ICZT allows a person to zoom in on the time span of interest by specifying the starting time, the time resolution, and the number of time steps.
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摘要 :
There exists a need to develop a method to locate underground voids, or caches. In the past, ground penetrating radar (GPR) operating in the time domain mode has been used. In this paper, we turn our attention to stepped frequency...
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There exists a need to develop a method to locate underground voids, or caches. In the past, ground penetrating radar (GPR) operating in the time domain mode has been used. In this paper, we turn our attention to stepped frequency radar, capable of making frequency domain reflection coefficient measurements. We then apply the inverse Chirp-Z transform (ICZT) to this data, generating a time domain response. The scenario under consideration is that of an airborne radar passing over the surface of the earth. The radar is directed toward the surface and is capable of measuring the reflection coefficient, seen looking toward the earth, as a function of frequency. The frequency domain -data in this work is simulated and is generated from a transmission line model of the problem. Using the ICZT we convert this frequency domain data to the time domain. Once in the time domain, reflections due to discontinuities appear at times indicating their relative distance from the source. The discontinuities occurring beyond the surface of the earth could be indicative of underground structures. The ICZT allows a person to zoom in on the time span of interest by specifying the starting time, the time resolution, and the number of time steps.
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Environmentally compatible disposal sites must be found despite all efforts to avoid and reduce the generation of dangerous waste. Deep geologic disposal provides the logical solution as ever more categories of waste are barred fr...
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Environmentally compatible disposal sites must be found despite all efforts to avoid and reduce the generation of dangerous waste. Deep geologic disposal provides the logical solution as ever more categories of waste are barred from long-term disposal in near-surface sites through regulation and litigation. Past mining in the US has left in its wake large volumes of suitable underground space. EPA studies and foreign practice have demonstrated deep geologic disposal in mines to be rational and viable. In the US, where much of the mined underground space is located on public lands, disposal in mines would also serve the goal of multiple use. It is only logical to return the residues of materials mined from the underground to their origin. Therefore, disposal of dangerous wastes in mined underground openings constitutes a perfect match between mining and the protection and enhancement of the environment.
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