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Ground penetrating radar: antenna frequencies and maximum probable depths of penetration in quaternary sediments
SITE INVESTIGATIONS:GEOPHYSICS measurements at various burial depths provided a systematic data base from which target responses, propagation parameters of the medium, and relevant data processing techniques were evaluated to gain useful insights into their interpretations. (from Authors)
958203 Ground penetrating radar: antenna frequencies and maximum probable depths of penetration in Quaternary sediments D. G. Smith & H. M. Jol, Journal of Applied Geophysics, 33(1-3), 1995, pp 93-100. The maximum probable depth of penetration of ground penetrating radar in Quaternary deposits is commonly unknown among GPR users because of the varying physical properties of sediments. In this paper GPR experiments were carried out in a gravel pit to determine maximum probable depths of penetration for 25, 50, 100 and 200 MHz antennas. With a 1000 V transmitter, 25 MHz antennas are capable of detecting stratigraphy to 52 m and possibly 57 m deep. Excessive signal losses for the 50, 100 and 200 MHz antennas occur at depths below 47, 37 and 28 m, respectively, preventing effective detection of stratigraphic interfaces. A comparison of results shows a linear trend between different antenna frequencies and the maximum probable depth of penetration, suggesting that the 12.5 MHz antennas can detect strata to 66 m deep. (from Authors)
958204 A laboratory scale model for the study of subsurface scattering in low-inss media with applications to ground penetrating radar I. C. Peden & J. Brew, Journal of Applied Geophysics, 33(13), 1995, pp 109-118. This study utilized a circular metal tank lined with microwave absorbing material and filled with a relatively inexpensive low-loss ceramic powder medium. Simulated boreholes, targets, scaled dipole antennas and haluns were constructed, and instrumentation operating in the 2-4 GHz band was assembled and automated. The result is a scale model measurement technique that has proven useful for tunnel detection investigations and that is neither unduly expensive nor difficult to implement. (from Authors)
958205 First results in autonomous retrieval of buried objects H. Herman & S. Singh, Automation in Construction, 4(2), 1995, pp 111-123. An autonomous system designed to detect, locate and retrieve buried objects is presented. The system is equipped with a surface and subsurface sensor. The surface sensor is a laser rangefinder. The subsurface sensor is a ground penetrating radar. First, subsurface sensing is used to detect and locate the buried objects. If the object can be reached with one dig, an excavator retrieves it directly. Otherwise a layer of soil above the object is removed and another subsurface scan is made to get a more accurate estimate of the object location. This loop is repeated until the object is retrieved. This paper presents some recent results in sensing and excavation, these include hazardous waste removal, maintenance of subsurface structure (e.g. gas pipes), construction, and removal of unexploded buried ordnance. (from Authors)
958206 Ground penetrating radar for the detection of liquid contaminants J. J. Daniels, R. Roberts & M. Vendl, Journal of Applied Geophysics, 33(1-3), 1995, pp 195-207. The significance of ground penetrating radar as a tool to detect near-surface contaminants is illustrated at a site in the
385A
Midwest representing petroleum product above the water table. Tests show that ground penetrating radar may provide a means of mapping hydrocarbons in the vadose zone. Results of controlled surveys in a sand test pit at The Ohio State University demonstrate conclusively that there is a clear GPR anomaly over containers of diesel fuel and containers containing the host sand material saturated with diesel fuel. (from Authors)
958207 Applications of ground penetrating radar in assessing some geological hazards: examples of groundwater contamination, faults, cavities A. g . Benson, Journal of Applied Geophysics, 33(1-3), 1995, pp 177-193. Ground penetrating radar can be used in appropriate geological settings to help map subsurface geological structures and groundwater contaminants. Case studies from sites in Arizona and Utah show that good correlation exists between GPR signatures and hydrocarbon contamination in strategically located wells. An example from along the Wasateh Fault Zone, Utah County, Utah, shows good correlation between GPR data and trench data. Finally, examples from Provo, Utah and Eureka, Utah demonstrate the utility of using GPR for locating underground excavations and/or cavities. (from Author)
958208 Burehole radar tunnel detection at Gjovik, Norway F. N. Kong, H. Westerdahl & T. L. By, Publikasjon - Norges Geotekniske Institutt, 194, 1994, 10 pp; reprinted from: Proc. 4th tunnel detection symposium, Golden, April 1993, pp 649658. Tomographie tests were pc_rformed both before and after the driving of a 10 x 10m2 tunnel in conjunction with the excavation of the Gjovik Olympic Mountain Hall. Test results indicate that the NGI georadar system functions well in the performance of borehole tomography measurements. The tomographic image obtained dearly shows the location and dimension of the tunnel. (Authors)
958209 Conventional and modern seismic investigations for rock quality determination at a dam site - a case history J. Louis, T. Papadopoulos, G. Drakatos & P. Pantzartzis, Geophysical Prospecting, 43(6), 1995, pp 779-792. Refraction seismies and modern tomographic surveys were employed at the Platanovrissi dam site on the Nestos river in northern Greece in an effort to investigate the dynamic elastic properties and roekmass condition of gneiss-schist outcropping in the area under investigation. Six seismic refraction traverses were run on the ground surface, inside the exploratory tunnels and between tunnels and the ground surface. The results provided information about the lowvelocity surface layer parameters and the stress relief zones on the walls of all the tunnels in which seismie tomography tests were performed. (from Authors)
958210 In-situ determination of macroscopic thermal neutron
absorption cross-section of borehole model materials using the integrated flux method S. A. Menn & H. E. Hall Jr, Nuclear Geophysics, 9(1), 1995, pp 45-54. The integratexl thermal neutron flux method of determining the macroscopic thermal neutron absorption eross-section of samples consisting of approx. 400 kg of unconsolidated geologic material, saturated with fresh water, to be used in borehole models is reported. One advantage of this method is the bulk cross-section determinations are made relative to a
958203 Ground penetrating radar: antenna frequencies and maximum probable depths of penetration in Quaternary sediments D. G. Smith & H. M. Jol, Journal of Applied Geophysics, 33(1-3), 1995, pp 93-100. The maximum probable depth of penetration of ground penetrating radar in Quaternary deposits is commonly unknown among GPR users because of the varying physical properties of sediments. In this paper GPR experiments were carried out in a gravel pit to determine maximum probable depths of penetration for 25, 50, 100 and 200 MHz antennas. With a 1000 V transmitter, 25 MHz antennas are capable of detecting stratigraphy to 52 m and possibly 57 m deep. Excessive signal losses for the 50, 100 and 200 MHz antennas occur at depths below 47, 37 and 28 m, respectively, preventing effective detection of stratigraphic interfaces. A comparison of results shows a linear trend between different antenna frequencies and the maximum probable depth of penetration, suggesting that the 12.5 MHz antennas can detect strata to 66 m deep. (from Authors)
958204 A laboratory scale model for the study of subsurface scattering in low-inss media with applications to ground penetrating radar I. C. Peden & J. Brew, Journal of Applied Geophysics, 33(13), 1995, pp 109-118. This study utilized a circular metal tank lined with microwave absorbing material and filled with a relatively inexpensive low-loss ceramic powder medium. Simulated boreholes, targets, scaled dipole antennas and haluns were constructed, and instrumentation operating in the 2-4 GHz band was assembled and automated. The result is a scale model measurement technique that has proven useful for tunnel detection investigations and that is neither unduly expensive nor difficult to implement. (from Authors)
958205 First results in autonomous retrieval of buried objects H. Herman & S. Singh, Automation in Construction, 4(2), 1995, pp 111-123. An autonomous system designed to detect, locate and retrieve buried objects is presented. The system is equipped with a surface and subsurface sensor. The surface sensor is a laser rangefinder. The subsurface sensor is a ground penetrating radar. First, subsurface sensing is used to detect and locate the buried objects. If the object can be reached with one dig, an excavator retrieves it directly. Otherwise a layer of soil above the object is removed and another subsurface scan is made to get a more accurate estimate of the object location. This loop is repeated until the object is retrieved. This paper presents some recent results in sensing and excavation, these include hazardous waste removal, maintenance of subsurface structure (e.g. gas pipes), construction, and removal of unexploded buried ordnance. (from Authors)
958206 Ground penetrating radar for the detection of liquid contaminants J. J. Daniels, R. Roberts & M. Vendl, Journal of Applied Geophysics, 33(1-3), 1995, pp 195-207. The significance of ground penetrating radar as a tool to detect near-surface contaminants is illustrated at a site in the
385A
Midwest representing petroleum product above the water table. Tests show that ground penetrating radar may provide a means of mapping hydrocarbons in the vadose zone. Results of controlled surveys in a sand test pit at The Ohio State University demonstrate conclusively that there is a clear GPR anomaly over containers of diesel fuel and containers containing the host sand material saturated with diesel fuel. (from Authors)
958207 Applications of ground penetrating radar in assessing some geological hazards: examples of groundwater contamination, faults, cavities A. g . Benson, Journal of Applied Geophysics, 33(1-3), 1995, pp 177-193. Ground penetrating radar can be used in appropriate geological settings to help map subsurface geological structures and groundwater contaminants. Case studies from sites in Arizona and Utah show that good correlation exists between GPR signatures and hydrocarbon contamination in strategically located wells. An example from along the Wasateh Fault Zone, Utah County, Utah, shows good correlation between GPR data and trench data. Finally, examples from Provo, Utah and Eureka, Utah demonstrate the utility of using GPR for locating underground excavations and/or cavities. (from Author)
958208 Burehole radar tunnel detection at Gjovik, Norway F. N. Kong, H. Westerdahl & T. L. By, Publikasjon - Norges Geotekniske Institutt, 194, 1994, 10 pp; reprinted from: Proc. 4th tunnel detection symposium, Golden, April 1993, pp 649658. Tomographie tests were pc_rformed both before and after the driving of a 10 x 10m2 tunnel in conjunction with the excavation of the Gjovik Olympic Mountain Hall. Test results indicate that the NGI georadar system functions well in the performance of borehole tomography measurements. The tomographic image obtained dearly shows the location and dimension of the tunnel. (Authors)
958209 Conventional and modern seismic investigations for rock quality determination at a dam site - a case history J. Louis, T. Papadopoulos, G. Drakatos & P. Pantzartzis, Geophysical Prospecting, 43(6), 1995, pp 779-792. Refraction seismies and modern tomographic surveys were employed at the Platanovrissi dam site on the Nestos river in northern Greece in an effort to investigate the dynamic elastic properties and roekmass condition of gneiss-schist outcropping in the area under investigation. Six seismic refraction traverses were run on the ground surface, inside the exploratory tunnels and between tunnels and the ground surface. The results provided information about the lowvelocity surface layer parameters and the stress relief zones on the walls of all the tunnels in which seismie tomography tests were performed. (from Authors)
958210 In-situ determination of macroscopic thermal neutron
absorption cross-section of borehole model materials using the integrated flux method S. A. Menn & H. E. Hall Jr, Nuclear Geophysics, 9(1), 1995, pp 45-54. The integratexl thermal neutron flux method of determining the macroscopic thermal neutron absorption eross-section of samples consisting of approx. 400 kg of unconsolidated geologic material, saturated with fresh water, to be used in borehole models is reported. One advantage of this method is the bulk cross-section determinations are made relative to a