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Detection of abandoned coal mine workings and underground voids by microgravity
314A
896203 Crosshole seismic tomography Bregman, N D; Bailey, R C; Chapman, C H Geophysics 1/54, N2, Feb 1989, P200-215 Many tomographic interpretations of crosshole seismic travel times assume linear raypaths connecting source and receiver. However, significant curvature may occur where velocity variations of 10-20% or more are found,and the simplified analysis is inaccurate. An interactive inversion scheme based on two dimensional ray tracing is applied to field data. The method iteratively ray traces and updates the velocity model. The procedure is continued until synthetic travel times fit the data to within experimental error or no improvement in fit is obtained. Its accuracy is demonstrated.
896204 Application of mode-converted shear waves to rock-property estimation from vertical seismic profiling data Ahmed, H Geophysics 1/54, N4, April 1989, P478-485 Three component vertical seismic profiling (3-CVSP) data were acquired and analysed. P and S wave interval velocities were computed from identified onset times at many seismometer positions along the borehole. The ratio of Vs/Vp is calculated and used to evaluate Poisson's ratio and ratio of bulk to shear modulus. In a North Sea well, the variation of elastic parameters correlated highly with changes in stratigraphy, and abrupt changes can indicate the gas-water to water transition zone.
896205 Determination of bedrock topography beneath the Greenland ice sheet by three-dimensional imaging of radar sounding data Fisher, E; McMechan, G A; Gorman, M R; Cooper, A P R; Aiken, C L V; Ander,M E; Zumberge, M A J Geophys Res V94, NB3, March 1989, P2874-2882 Large numbers of radar reflections were obtained along 124 radial lines 5km long in southern Greenland in 1987. They have been processed using a three dimensional kinematic migration algorithm to produce a high resolution profile of rock surface topography beneath the ice sheet. Theory and application of the algorithm are presented and accuracy of the results discussed.
896206 Calibration of frequency-domain electromagnetic induction meters and their possible use in recharge studies Cook, P G; Hughes, M W; Walker, G R; Allison, G B J Hydrol N107, N1/4, 30 May 1989. P251-265 Published models of soil conductivity are used to develop a calibration for frequency domain electromagnetic induction meters which is not site specific, and requires only knowledge of certain soil properties. One critical soil property is the impedance factor, a function of soil water content. The calibration is then used to model the response of the soil to variations in soil water salinity resulting from variations in groundwater recharge rate. Modelled relations and field data are in good agreement.
896207 Detection of abandoned coal mine workings and underground voids by microgravity Butler, D Min Engng V41, N4, April 1989, P245-247 A microgravity survey can detect voids, variations in depth to bedrock and geological structures. Some easy to use curves for anomaly variation, adapted from Arzi (1974), are presented.
Evaluation of noise sources is important and is discussed. A case study is presented to illustrate anomaly and noise evaluation, detection of water filled and air filled cut outs.
896208 Rotary pressure sounding: 20 years of experience Rygg, N O; Andresen, A A Norw Geoteeh Inst Publ N177, 1989, 5P The rotary-pressure sounding method has been developed to provide a quick and reliable picture of soil conditions and depth to bedrock. The equipment is operated by a multi purpose drilling rig and consists of a bit extended by rods with flush couplings. The method is being used in Norway to locate quick clays. Research is underway to combine the rotary pressure sounding with percussion rock drilling to develop equipment which will penetrate all sorts of soils.
896209 Crosshole seismics including geotomography for investigation of foundations By, T L Norw Geotech lnst Pabl N177, 1989, 12P The instrumentation and procedure for the cross-hole seismic method, and 3 examples of its application are described. F o r clear images the method should be used with tomography. At Oddatjorn dam, the cross-hole seismic method was used to investigate the fractured rockmass under the left abutment in order to control the grout curtain. At Svartisen HEP scheme the method was used to detect the extent of karst formations. Geotomography was used for rock mass characterisation and prediction of seepage problems for 2 road tunnels under Osio.
896210 Inductive coupling for a conductive dyke in a resistive Earth Charters, R A; Dosso, H W; Best, M E; Nienaber, W Phys Earth Planet Inter V54, N1/2, April 1989, P140-148 An analytical model of inductive coupling for a conductive dyke in a resistive earth for a dipole source and receiver is developed. It is calibrated using results from laboratory analogue modelling. Using the obtained geometric loop parameters, the analytical model gives good agreement with laboratory results over the entire traverse, including locations directly above the dyke. These results have applications in separating inductive coupling and induced polarization components in spectral IP measurements.
896211 Determination by the radio-wave method of weakened zones in the bases of structures being constructed in karstified territories Zaderigolova, M M Soil Meeh Found Engng V25. N4, July-Aug 1988, P162-165 Geophysical methods have achieved some success in locating underground cavities, but have met problems because of high noise levels in industrial areas, high resistivity cover of karstified zones, need for conductive coupling with the ground, and signal processing complexity. These can be overcome using the radio wave method in the frequency range 0.1-10 MHz. The apparatus, techniques, and results are presented. The major drawbacks are limited penetration (30-40m), and effects of rugged relief.
~, 1989 Pergamon Press plc. Reproduction not permitted
896203 Crosshole seismic tomography Bregman, N D; Bailey, R C; Chapman, C H Geophysics 1/54, N2, Feb 1989, P200-215 Many tomographic interpretations of crosshole seismic travel times assume linear raypaths connecting source and receiver. However, significant curvature may occur where velocity variations of 10-20% or more are found,and the simplified analysis is inaccurate. An interactive inversion scheme based on two dimensional ray tracing is applied to field data. The method iteratively ray traces and updates the velocity model. The procedure is continued until synthetic travel times fit the data to within experimental error or no improvement in fit is obtained. Its accuracy is demonstrated.
896204 Application of mode-converted shear waves to rock-property estimation from vertical seismic profiling data Ahmed, H Geophysics 1/54, N4, April 1989, P478-485 Three component vertical seismic profiling (3-CVSP) data were acquired and analysed. P and S wave interval velocities were computed from identified onset times at many seismometer positions along the borehole. The ratio of Vs/Vp is calculated and used to evaluate Poisson's ratio and ratio of bulk to shear modulus. In a North Sea well, the variation of elastic parameters correlated highly with changes in stratigraphy, and abrupt changes can indicate the gas-water to water transition zone.
896205 Determination of bedrock topography beneath the Greenland ice sheet by three-dimensional imaging of radar sounding data Fisher, E; McMechan, G A; Gorman, M R; Cooper, A P R; Aiken, C L V; Ander,M E; Zumberge, M A J Geophys Res V94, NB3, March 1989, P2874-2882 Large numbers of radar reflections were obtained along 124 radial lines 5km long in southern Greenland in 1987. They have been processed using a three dimensional kinematic migration algorithm to produce a high resolution profile of rock surface topography beneath the ice sheet. Theory and application of the algorithm are presented and accuracy of the results discussed.
896206 Calibration of frequency-domain electromagnetic induction meters and their possible use in recharge studies Cook, P G; Hughes, M W; Walker, G R; Allison, G B J Hydrol N107, N1/4, 30 May 1989. P251-265 Published models of soil conductivity are used to develop a calibration for frequency domain electromagnetic induction meters which is not site specific, and requires only knowledge of certain soil properties. One critical soil property is the impedance factor, a function of soil water content. The calibration is then used to model the response of the soil to variations in soil water salinity resulting from variations in groundwater recharge rate. Modelled relations and field data are in good agreement.
896207 Detection of abandoned coal mine workings and underground voids by microgravity Butler, D Min Engng V41, N4, April 1989, P245-247 A microgravity survey can detect voids, variations in depth to bedrock and geological structures. Some easy to use curves for anomaly variation, adapted from Arzi (1974), are presented.
Evaluation of noise sources is important and is discussed. A case study is presented to illustrate anomaly and noise evaluation, detection of water filled and air filled cut outs.
896208 Rotary pressure sounding: 20 years of experience Rygg, N O; Andresen, A A Norw Geoteeh Inst Publ N177, 1989, 5P The rotary-pressure sounding method has been developed to provide a quick and reliable picture of soil conditions and depth to bedrock. The equipment is operated by a multi purpose drilling rig and consists of a bit extended by rods with flush couplings. The method is being used in Norway to locate quick clays. Research is underway to combine the rotary pressure sounding with percussion rock drilling to develop equipment which will penetrate all sorts of soils.
896209 Crosshole seismics including geotomography for investigation of foundations By, T L Norw Geotech lnst Pabl N177, 1989, 12P The instrumentation and procedure for the cross-hole seismic method, and 3 examples of its application are described. F o r clear images the method should be used with tomography. At Oddatjorn dam, the cross-hole seismic method was used to investigate the fractured rockmass under the left abutment in order to control the grout curtain. At Svartisen HEP scheme the method was used to detect the extent of karst formations. Geotomography was used for rock mass characterisation and prediction of seepage problems for 2 road tunnels under Osio.
896210 Inductive coupling for a conductive dyke in a resistive Earth Charters, R A; Dosso, H W; Best, M E; Nienaber, W Phys Earth Planet Inter V54, N1/2, April 1989, P140-148 An analytical model of inductive coupling for a conductive dyke in a resistive earth for a dipole source and receiver is developed. It is calibrated using results from laboratory analogue modelling. Using the obtained geometric loop parameters, the analytical model gives good agreement with laboratory results over the entire traverse, including locations directly above the dyke. These results have applications in separating inductive coupling and induced polarization components in spectral IP measurements.
896211 Determination by the radio-wave method of weakened zones in the bases of structures being constructed in karstified territories Zaderigolova, M M Soil Meeh Found Engng V25. N4, July-Aug 1988, P162-165 Geophysical methods have achieved some success in locating underground cavities, but have met problems because of high noise levels in industrial areas, high resistivity cover of karstified zones, need for conductive coupling with the ground, and signal processing complexity. These can be overcome using the radio wave method in the frequency range 0.1-10 MHz. The apparatus, techniques, and results are presented. The major drawbacks are limited penetration (30-40m), and effects of rugged relief.
~, 1989 Pergamon Press plc. Reproduction not permitted