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  • Articles  (11)
  • strata control  (6)
  • Fault  (5)
  • Springer  (11)
  • American Meteorological Society
  • American Physical Society (APS)
  • De Gruyter
  • International Union of Crystallography
  • Wiley
  • 2000-2004
  • 1995-1999
  • 1980-1984  (11)
  • 1935-1939
  • 1930-1934
  • 1984  (11)
  • 1959
  • 1937
  • Geosciences  (11)
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  • Articles  (11)
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  • Springer  (11)
  • American Meteorological Society
  • American Physical Society (APS)
  • De Gruyter
  • International Union of Crystallography
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Years
  • 2000-2004
  • 1995-1999
  • 1980-1984  (11)
  • 1935-1939
  • 1930-1934
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  • 1
    Electronic Resource
    Electronic Resource
    Pore-fluid pressures and frictional heating on a fault surface (1984)
    Springer
    Pure and applied geophysics 122 (1984), S. 583-607 
    Details
    ISSN: 1420-9136
    Keywords: Fault ; Pore-fluid pressure ; Frictional heating ; Numerical modeling ; Stress
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract This study considers the effects of heat transfer and fluid flow on the thernal, hydrologic, and mechanical response of a fault surface during seismic failure. Numerical modeling techniques are used to account for the coupling of the thermal, fluid-pressure, and stress fields. Results indicate that during an earthquake the failure surface is heated to a tempeature required for the thermal expansion of pore fluids to balance the rate of fluid loss due to flow and the fluid-volume changes due to pore dilatation. Once this condition is established, the pore fluids pressurize and the shear strength decreases rapidly to a value sufficient to maintain the thermal pressurization of pore fluids at near-lithostatic values. If the initial fluid pressure is hydrostatic, the final temperature attained on the failure surface will increase with depth, because a greater pressure increase can occur before a near-lithostatic pressure is reached. The rate at which thermal pressurization proceeds depends primarily on the hydraulic characteristics of the surrounding porous medium, the coefficient of friction on the fault surface, and the slip velocity. If either the permeability exceeds 10−15 m2 or the porous medium compressibility exceeds 10−8 Pa−1, then frictional melting may occur on the fault surface before thermal pressurization becomes significant. If the coefficient of friction is less than 10−1 and if the slip velocity is less than 10−2 msec−1, then it is doubtful that either thermal pressurization or frictional melting on the fault surface could cause a reduction in the dynamic shear strength of a fault during an earthquake event.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00874618
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  • 2
    Electronic Resource
    Electronic Resource
    Discharge of H2 from the Atotsugawa and Ushikubi Faults, Japan, and its relation to earthquakes (1984)
    Springer
    Pure and applied geophysics 122 (1984), S. 185-193 
    Details
    ISSN: 1420-9136
    Keywords: Hydrogen ; Soil gas ; Fault ; Earthquake
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The concentration of H2 in soil gases has been measured weekly at five stations on the Atotsugawa and Ushikubi faults in northern central Main Island, Japan, since 1981 in search of possible relationship with earthquakes. The observed H2 concentration varies from lower than 1 ppm to 7.8% in time and place. When a large earthquake (M: 7.7, epicenter distance: 486 km) occurred on 26 May 1983, an outstanding discharge of H2 was observed at all five stations, preseismically at three of them, and coseismically at the other two. Simultaneous H2 emission was also observed at some stations in seven other occasions. These periods of unusual H2 discharge nearly coincided with occurrences of major earthquakes in Japan, but not of local minor earthquakes along the Atotsugawa fault. This fault, being a deep fracture zone, may be sensitive to large-scale crustal stress changes which incidentally cause the major earthquakes. Increased H2 may be produced by rock fracture caused by the increased stresses on the fault and by the earthquakes themselves. Local minor earthquakes along Atotsugawa fault with magnitude lower than 3 may be unable to cause sufficient rock fracture to produce significant H2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00874592
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  • 3
    Electronic Resource
    Electronic Resource
    Instability on a weakening fault (1984)
    Springer
    Pure and applied geophysics 122 (1984), S. 478-491 
    Details
    ISSN: 1420-9136
    Keywords: Instability ; Fault ; Stick-slip ; Stress ; Friction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Weakening of a prestressed sawcut in Westerly granite under laboratory condition is accomplished by injecting pressurized fluid into the sawcut. After injection a sequence of stick-slips is observed while the deviatoric stress decreases successively with each stick-slip. On the basis of the experimental observation we develop a model of fault instability due to inhomogeneous and progressive weakening of the fault. According to this model, the fault surface is divided into the ‘slipped’ and the ‘locked’ regions, depending on whether or not the local state of stress satisfies the friction criterion. The average shear stress in the slipped region decreases with time and, in order to maintain a quasi-static equilibrium, shear stress in the remaining ‘locked’ region on the fault surface increases. This situation may last until a critical state of stress on the fault is met, at which a sudden instability (stick0slip) may occur. We suggest that this mechanism of stress transfer may be a viable mechanism of induced seismicity and aftershocks, in addition to the well-known mechanism of a local increase of pore pressure. By comparing the experimental data with model predictions we show that the critical condition for slip instability is when the average shear stress over the ‘locked’ region becomes equal to the value given by the friction criterion. Thus the friction criterion established for slip on fractures on which the state of stress is macroscopically uniform may also be applicable to fractures on which the stress state is macroscopically heterogeneous.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00874613
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  • 4
    Electronic Resource
    Electronic Resource
    The detection and interpretation of hydrogen in fault gases (1984)
    Springer
    Pure and applied geophysics 122 (1984), S. 392-402 
    Details
    ISSN: 1420-9136
    Keywords: Hydrogen ; Fault ; Soil gas ; Earthquake ; CH4
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Hydrogen gas can be released by chemical and mechanical changes in crustal rocks. Once released, it is highly mobile, buoyant, and almost insoluble in groundwater. A fault system may act as a conduit, allowing hydrogen to accumulate in soil gases near a surface expression. Since hydrogen is scarce in ambient air, its presence at elevated levels in soil gases may be a tool for fault mapping. In order to evaluate this tool, we surveyed eleven different faults by measuring the concentration of hydrogen and methane in 2 to 21 soil-gas samples that were collected near each of them. The sense of motion at four of those faults is normal (western United States, Greece), at five it is strike-slip or dip-slip (California, Colorado, Japan), and at two it is thrusting (California). At four of these faults (Hebgen Lake, Yellowstone, Yamasaki, Burro Mountain) maximum concentrations of hydrogen ranged from 80 ppm to 70% and methane from 300 ppm to 5%. All other sites showed ambient levels of both gases, except for one sample taken at Mt. Borah, Idaho, that was 2% methane. From this preliminary study it is not clear whether the presence of hydrogen is correlated uniquely to the location of faults or whether it occurs randomly. The conditions required to produced and accumulate hydrogen are also not clear. Excess hydrogen may well be produced by different mechanisms in different geological regimes. For example, if ferrous hydroxide is present in local rocks, it may react to produce hydrogen. Detailed and extensive studies are needed to clarify the connection between hydrogen and tectonic faulting.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00874607
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  • 5
    Electronic Resource
    Electronic Resource
    Can injection tests reveal the potential for fault movements? (1984)
    Springer
    Pure and applied geophysics 122 (1984), S. 608-618 
    Details
    ISSN: 1420-9136
    Keywords: Fault ; Fracture ; Hydrochemical ; Flud injection ; Permeability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The role of fluids in faulting mechanism and triggering earthquakes is widely accepted. The effective-stress law is the basis for the postulated theories. Using a generalized version of this law, applicable to both continuum and discontinuities, hydromechanical behaviour of a horizontal fracture in a hypothetical fluid-injection problem is investigated. In this problem the increasing intake flow rates, unpredictable by the traditional fluid-flow solutions, brings out another significant aspect of the role of the fluid pressure in rocks. By reducing the magnitude of the compressive effective stresses the fluid pressure causes elastic recovery in fractures. Simple rheologic models are used to demonstrate this fact. Such effects may lead to permeability increases in the rock mass, depending on the magnitude of the fluid pressure. Such variations in permeability, however, are governed by the path dependency of the fracture-deformation response. Therefore, a significant increase in permeability is an indication of comparability of the state of stress and the applied fluid pressure. This index may reveal the potential of hydroactivation of faults, as may arise in the regions of dam reservoirs, underground waste injections, and known faults, for certain ranges of working pressures relevant to each of the above-cited situations. Fluid-injection tests under constant working pressures are suggested as a means revealing the likelihood of movement on the faults.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00874619
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  • 6
    Electronic Resource
    Electronic Resource
    Computer aided design and strata control (1984)
    Springer
    Geotechnical and geological engineering 2 (1984), S. 43-49 
    Details
    ISSN: 1573-1529
    Keywords: Coal mining ; strata control ; computer-aided design ; mine planning: steep seam working
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Summary Research into strata control has been pursued at Cerchar for the last 20 years, and has led to the definition of rules for the siting of new mine workings. These rules are drawn up as a function of the ‘volume of influence’ which is exerted by existing workings. To facilitate their application by the coal producer, a computer-aided design system for steep-seam faces has been developed on a minicomputer. The main features of the interactions which occur within the volume of influence of such faces are restated and the system which has been developed for design is described, with particular emphasis on the design stages which involved graphic systems and data base management.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00880856
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  • 7
    Electronic Resource
    Electronic Resource
    Use of rock classification to estimate roof caving span in oblong workings (1984)
    Springer
    Geotechnical and geological engineering 2 (1984), S. 133-140 
    Details
    ISSN: 1573-1529
    Keywords: Rock classification ; longwall mining ; strata control ; mine openings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Summary Indian coal measures have widely varying caving characteristics. The maximum roof span of a longwall or depillaring panel at the time of nether roof collapse is shown to have a direct relation withRQD from a study of 12 case histories. A similar relation between maximum unsupported span of openings and rock mass quality as defined by theQ-system was also demonstrated. A simple nomogram is presented to predict the face advance required to cause roof collapse when theRQD or rock mass quality is known.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00880878
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  • 8
    Electronic Resource
    Electronic Resource
    Validation and error analysis of a strata modelling technique (1984)
    Springer
    Geotechnical and geological engineering 2 (1984), S. 305-321 
    Details
    ISSN: 1573-1529
    Keywords: Coal mining ; finite difference analysis ; error analysis ; strata control
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Summary Sources of error are investigated for a two-dimensional finite difference computer program designed to model strata deformation. The program calculates the displacements of a mesh of ‘mass points’, by the iterative solution of equations of equilibrium for the stresses acting on each mass point. The effect of errors on both displacement estimates and stress estimates is considered. Round-off errors are discussed analytically, while the effect of choosing too coarse a mesh density is demonstrated by comparison of two runs of the program with identical material properties, but different mesh densities. The influence of boundary conditions and the result of incomplete relaxation of the finite difference equations is estimated by comparison with Kirsch's analytical solution for a thin plate of finite width with a circular hole under unidimensional load. As a result of the analysis, estimators for stresses and displacements are derived, which make allowance for some of the sources of error; suitable boundary conditions for first and subsequent runs of the program are proposed; and a convergence criterion for the iterative process is suggested. These results are then applied to simulations of mining situations, together with various refinements of the basic model, such as separation and ‘slip’ between adjacent strata, and an allowance for failure of material.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00881119
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  • 9
    Electronic Resource
    Electronic Resource
    Stochastic methods for the prediction of strata behaviour (1984)
    Springer
    Geotechnical and geological engineering 2 (1984), S. 291-304 
    Details
    ISSN: 1573-1529
    Keywords: Coal mining ; strata control ; finite difference analysis ; stochastic methods
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Summary A two-dimensional finite difference computer program, with the facility to represent stratified material by means of a mesh of ‘mass points’ with different material properties in each square of the mesh, is adapted to run on a mesh whose material properties are selected stochastically from a specified distribution. The program uses an iterative method to solve the equations of equilibrium, giving estimates of displacements and stresses. Lattices of normally distributed (zero mean, unit variance) random values are produced: lattices of statistically independent values and lattices whose values are spatially correlated, to give the effect of gradual variations resulting in regions of positive values and regions of negative values. These lattices are used to generate the material properties: Young's modulus, Poisson's ratio and density. Each property has a specified mean and standard deviation for each material in the model, and the precise values for each mass point are calculated from the relevant lattices. A simple model with a square opening is used to investigate the effect of this stochastic generation of material properties, by comparison of stresses and displacements near the opening for runs of the program with (1) deterministic and (2) stochastic properties. Similar lattices of random values are used to introduce a stochastic element in the criterion for failure of materials. This is applied to a more realistic simulation of a mining situation, where Mohr's Criterion is used, with a stochastic component, to determine whether failure has occurred at each point of the mesh.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00881118
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  • 10
    Electronic Resource
    Electronic Resource
    Astrata control system and its application in West German coal mining (1984)
    Springer
    Geotechnical and geological engineering 2 (1984), S. 119-132 
    Details
    ISSN: 1573-1529
    Keywords: Coal mining ; strata control ; rock pressure ; mine planning ; longwall mining
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Summary Astrata control system has been developed to improve mine planning and design in deep coal mines in West Germany, where redistributed stresses from longwall workings in weak strata create difficult support problems. The system involves theoretical, laboratory and underground observations and studies of strata and support performance. Examples of the system covered in detail include planning the position and support of a cross-cut; improving a face layout; planning a gateroad; planning strata bolting and planning longwall face layouts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00880877
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