Anisotropic features of geometry and permeability in fractured rock masses

Anisotropic features of geometry and permeability in fractured rock masses

264A SITE INVESTIGATIONS:GEOPHYSICS 966184 Significance of discontinuity surveying in motorway alignment selection, southern Turkey I. Yilmazer, Eng...

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966184 Significance of discontinuity surveying in motorway alignment selection, southern Turkey I. Yilmazer, Engineering Geology, 40(1-2), 1995, pp 41-48. A case study from the Tarsus-Adana-Gaziantep motorway being constructed in southern Turkey displays well the role of a discontinuity survey in engineering geological and geotechnical work. The survey, which was carried out by visual inspection and practical field tests, indicated, on the basis of the consistency of the discontinuity systems in each rock exposure, that the suspected floating blocks were outcrops of in situ rock. Misinterpretation of the actual ground condition caused loss of both time and money. (from Author)

Geophysical techniques 966185 Ground geophysical study for development and exploration of E! Missikat radioactive minerals prospect, central Eastern Desert of Egypt E. M. Elkattan, H. S. Sadek, S. I. Rabie & H. I. Hassanein, Nuclear Geophysics, 9(4), 1995, pp 363-382. The importance of the area originates from previous studies, including airborne geophysics, surface geology and mining geology which indicate that the area has features of radioactive mineralization at the northeastern periphary of G. El Missikat. The present study deals with the use of ground geophysical methods (total-count radiometric and magnetic) in the exploration of radioactive mineralization and their relation to the geology and structural pattern of the area. (from Authors) 966186 Use of geophysical surveys during the planning, construction and remediation of landfills J. M. Reynolds & D. I. Taylor, in: Engineering geology of waste disposal, ed S.P. Bentley, (Geological Society of London; Engineering Geology Special Publication, 11), 1996, pp 93-98. Concurs that with current developments in data acquisition, processing, display and interpretation of geophysical data, the scope of environmental applications where multi-method geophysical surveys can be used is increasing rapidly. The range of geophysical methods currently available provides a powerful suite of investigative tools which complement direct observations. (from Authors) 966187 Formalized tracing of faults using geophysical data O. K. Tyapkin, Geophysical Journal, 14(1), 1994, pp 83-90. One of the most important methods for detailed studies is the study of fault structures whose indicators are 'fine' linear characteristics of physical fields. Using models, accuracy in determining the azimuths of the strike of linear features of spatially discretized physical fields was estimated. The possibility was studied of false tectonics of non-geological nature in the course of formalized processing of geophysical data, i.e. tectonics that can be characterized by methodology features of data acquisition and processing. (Author) 966188 Improvements in shallow high-resolution seismic reflection through PC-based systems R. D. Miller, R. D. Markiewicz, C. Mercy, Jianghai Xia & C. G. Maples, Computers & Geoseiences, 21(8), 1995, pp 957964. Increased dynamic range of recording equipment and decreased cost of processing hardware and software have made seismic reflection a cost-effective way of imaging geologic targets significant to environmental site classification. Some applications with demonstrated success include fault mapping with less than 4 m of vertical resolution at 300 m, detecting structure and stratigraphy associated with a hydrologic basin divide, and groundwater modeling of thick

sequences of alluvial, colluvial, and glacio-fluvial material. (from Authors) 966189 Anisotropic features of geometry and permeability in fractured rock masses Xing Zhang & D. J. Sanderson, Engineering Geology, 40(12), 1995, pp 65-75. A geometric anisotropy factor (,,If) of two-dimensional, natural fracture systems has been defined according to fracture spacing and orientation in a given direction. Geometric anisotropy of fracture systems has a major effect on the percolation threshold (the critical fracture density) of fracture systems below which the overall permeability is zero. A two-dimensional distinct element code (UDEC) has been used to calculate directional flow-rate of fracture systems. Simulated and natural fracture patterns, have been tested to examine the relation between geometric anisotropy and permeability anisotropy, which is demonstrated to have a power-law form. Also, the differential anisotropy factor (,4/) results in different universal exponents which govern the relation between fracture density and flow rates. (Authors) 966190 Oberflachenwellendaten zur Lokalisierung von Altlasten: ein Feldfall (Surface wave measurements for the location of waste deposits: a field study) C. Schneider & L. Dresen, Geophysical Transactions - Eotvos Lorand Geophysical Institute of Hungary, 39(4), 1994, pp 233-253. Describes the use of Rayleigh waves to detect near-surface inhomogenenus objects, like waste deposits etc. Rayleigh wave recordings have been integrated into conventional refraction seismic surveys at insignificant cost. It is shown that the Rayleigh wave technique is suitable for locating objects in layered media. A special dispersion analysis has been developed for delineating laterally heterogeneous nearsurface media. This method does not need any a-priori information about the underground. As a result, local dispersion curves are obtained, which represent the underground for any geophone position. The lateral variation of the surface wave signals is deduced from the variation of the local dispersion curves. In areas of smooth lateral variation dispersion curves can-be used within a rigorous inversion. This inversion leads to block-representations of the medium. Rayleigh wave signals can also be recompressed to improve resolution. (from English summary) 966191 Dolt reteges foldtani szerkezetek geoelektromos kututasi lehetosegenek vizsgalata anafitikus eloremodellezessel (Geological investigation of dipping beds with analytical forward modelling) A. Gyulai, Magyar Geofizika, 36(1), 1995, pp 40-67. The paper reviews potential field equations over a dipping bed. It presents apparent resistivity equations for different geoelectrical configurations. Apparent resistivity sections are computed perpendicularly to the strike of structures conraining at least two layers. Parameter sensitivities are defined for dipping beds and geoelectric configurations are investigated on the basis of parameter sensitivities to select the optimum geoelectrical array for exploration. (from English summary) 966192 Basis for a flexible low-cost automated resistivity data acquisition and analysis system M. A. Meju & M. Montague, Computers & Geosciences, 21(8), 1995, pp 993-999. An efficient and versatile automatic resistivity data acquisition and analysis system has been developed for use with any 4-eleetrode output resistivity meter. The acquisition hardware comprises a low-cost Digital Switching Unit which can be interfaced to a portable field microcomputer and a resistivity