30A

8312b,6

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

DOUBLE GAg~A-RAY PROBE AND THE AssOCIATED DR~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 den- sity at different depths of most materials used in civil emgineering. It is possible to deter- mine the wet demsities of one or more layers of material %hrough a vertical axis. This instru- ment is particularly UsefUl for assessing Or test- ing the efficacity of laying procedures area com- pactors: it can also de~ect the presence of voids or segregation in materials, control the thick- uess 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 prin- ciple of operation of the double probe, and describes the instrument and its associated drilling apparatus.

Geophysical techniques

8312~7 SUBSURFACE GRAVITY MEASUR~NTS AND DENSITY MAPPING IN THE ~AILAR~4 COPs~ 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 ~fHODS FOR STUDY OF COAL SFJNS IN P~/TrS OF THE PC~GANJ co.~ (~)

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 hori- zontal profiling. The vertical distribution of resistivity has been studied using Schlmmberger configuration at different locations along the profile. Laboratary studies of resistivity in- dicated the presenae of a good r~sistivity con- trast between ÷~he coal seams ani the surroumding formations. The field results did not bear this out: the resistivity responses of the coal form- ations 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 res- istivity ~aly over the coal seams. Two-elec- trode profiles are less noisy than Wenuer pro- files. 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 resis- tivity curves.

831249 TUNNEL RESOLUTION INVESTIGATION USING AN AL'I~O - MATED RESISTMTY TAI~ ANALOG

Kar~atowski, J; HabberJam, G M Geophys Prospect, V29, N6, Dec 1981, i~91-905

Describes the development of a tank analo~ 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 met- hods 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, P160- 166. Publ Morganto~n: West Virginia Univer- sity, 1981

Three project case histories are used to illus- trate 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 move- ments 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, 15213 u~

Subjects Peripheral to Geomechanics Snow and ice mechanics

831254 MECHANICAL PROP~IES OF SN~ Salm, B Revs Geophys Space Phys, V20, NI, Feb 1962,

PI-19