Applications of reflection seismics to mapping coal seam structure and discontinuities

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~rilling a ~ evaluation l~oblems are easily solved f ~ d e e p Tuscaloosa wells, using resistIvlty logs. Log reslstivitles in soft shales are linked to impem~Ing Ix~e p r e s ~ e reversals in deep samds, hlgh-resistivity hard shales are linked to lost circulation intervals, amd resistivlty invasion profiles a r e linked to freshwater anumalAes in boreholes with oll mud.

8312b,6 DOUBLE GAg~A-RAY PROBE AND THE AssOCIATED D R ~ U ~ APPARATUS (ZN ~E~C~) Valeux, J C Bull Liaison Lab Fonts Chausees, NI20, July-

Aug 1982, P33-39 The double gasmm-ray probe is an instrument for measuring, by gam~a-r%y transmission, the density at different depths of most materials used in civil emgineering. It is possible to determine the wet demsities of one or more layers of material %hrough a vertical axis. This instrument is particularly UsefUl for assessing Or testing the efficacity of laying procedures area compactors: it can also de~ect the presence of voids or segregation in materials, control the thickuess of different courses after laying, follow up the evolution of densities in an embankment over a period of time, and track the movements of water in soils. This article reviews the principle of operation of the double probe, and describes t h e instrument and its associated drilling apparatus.

Geophysical techniques

831249 TUNNEL RESOLUTION INVESTIGATION USING AN AL'I~OMATED R E S I S T M T Y TAI~ ANALOG Kar~atowski, J; HabberJam, G M Geophys Prospect, V29, N6, Dec 1981, i~91-905 Describes the development of a tank a n a l o ~ and gives a practical example of its use in the ~ o blem of resolving and discriminating between 2 horizontal cylimdrical tunnels. 831250 MAPPING OF CRACK EDGES BY SEISMIC METHODS Achenbach, J D; Norris, A; Vlswanathan, K Bull Seismol Soc Am, V72, N3, June 1982, P779-

792 The inverse problem of elastic wave diffraction by the edge of a large crack is investigated on the basis of elastodynamic ray theory and the geometrical theory of diffraction. Two methods are discussed for the mappir~ of the edge of a crack-like flaw in a homogeneous, isotropic, linearly elastic solid: a global triamgulation method and a local mapping technique. 831251 MULTICHANNEL ROCK NOISE MONITORING SYSTEM Go~d, T N; Rao, M V M S J Mine, Met Fuel, V?9, Ng-10, Sept-Oct 1981,

P288-2~0 831252 APPLICATIONS OF REFLECTION SEI~ICS TO MAPPING COAL SEAM STRUCTURE AND DISCONTINUITIES Dobecki, T L; Bartel, L C Proc 1st Conference on Ground Control in ~ning, Morganto~n, 27-29 July 1981, P160166. Publ Morganto~n: West Virginia University, 1981

8312~7 SUBSURFACE GRAVITY M E A S U R ~ N T S

AND DENSITY MAPPING IN THE ~AILAR~4 C O P s ~ MINES, ANDKIR.~. PRADESH, INDIA Satyam~ray~na Murty, B V; Ghy~suddin, M; Venkat Reddy, P Geophys Prospect, V30, N~, Aug 1982, Ph/~4-~53

Reports gravity measurements in 3 levels up to 100m depth and compares density maps produced with the distribution of the copper orebodles. 831258 USE OF ELECTRIC.~L RESISTIVITY ~ f H O D S FOR STUDY OF COAL SFJNS IN P~/TrS OF THE P C ~ G A N J

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Verma, R K; Bardopadhyay, T K; Bhuin, N C Geophys Prospect, V30, N!, Feb 1982, PI15-126 Different electrode conflgurat~ions, viz., Wenmer, two-electrode and half-Schlumberger, have been used with different electrode spacings in horizontal profiling. The vertical distribution of resistivity has been studied using Schlmmberger configuration at different locations along the profile. Laboratary studies of resistivity indicated the presenae of a good r~sistivity contrast between ÷~he coal seams ani the surroumding formations. The field results did not bear this out: the resistivity responses of the coal formations on the profiles a~i sourzling curves are not as clear as one would expect for such high contents. The Wenme~ profiles show a broad resistivity ~ a l y over the coal seams. Two-electrode profiles are less noisy than Wenuer profiles. Sharp peaks have been observed over the coal seams. The half-Schl~m~erger configuration seems the best: all the coal seams and their edges can be accurately outlined on the resistivity curves.

Three project case histories are used to illustrate the application of reflection seismology in determining continuity of coal seams. Each project uses different techniques and energy sources •

831253 MICROSEISMIC SYSTEM FOR MONITORING SLOPE STABILITY Lepper, C M; Polard, A P; Mullls, C T US Bureau of Mines report RI 8641, 1982, 64P Microselamic energy is generated when stresses acc~ated in rock formtions are released in the form of fracturing. The acoustic emissions resulting from these rock fractures amd movements are detectable as velocity sigmals in the earth near the energy source. A Bureau of Mines microseismic system that is capable of detecting the acoustic emissions from pit slope movements is described. The digital circuitry imc~l~'ated in the system allows a mlcrol~ocessc~ Irc~ram to immediately calculate and l~esent the location coomdinates for the seismic energy source in the mime pit wall. Avail: US~M, 4800 Forbes Avenue, Pittsburgh, Pa,

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Subjects Peripheral to Geomechanics Snow and ice mechanics 831254 MECHANICAL P R O P ~ I E S OF S N ~ Salm, B Revs Geophys Space Phys, V20, NI, Feb 1962, PI-19