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Estimation of confidence bounds for mean trace length of discontinuities using surveys. Technical note
29A
Remote
sensing and photographic techniques
911223
Determining the age of failure of motorway earthworks from aerial survey photographs Andrews, R D Transport Road Research Laboratory Research Report N257, 1990, 22P Knowledge of earth structure working life is important for maintenance planning and design. Aerial survey photographs of MI, M4, M5, and M45 sections were examined for evidence of failures. Difficulties in recognising signs of failure are described, and uncertainty in data was taken into account in analysis. Failures were seen for a wide variety of earth materials. Cuttings showed failure rate increasing, sometimes abruptly, after several years. Embankments showed more erratic behaviour. In neither case can it be assumed that apparently stable slopes will not fail in the future. Influence of weathering of slope materials on failure merits further investigation. Raw data were of insufficient quality to attempt analysis of effects of weather on failure rates.
Structural and geotechnical mapping See also: 911140 911224
Engineering geological maps: a cost benefit analysis De Mulder, E F J Environ Geol Water Sci 1/16, NI, July/Aug 1990, P23-28 An eight-step procedure for cost-benefit analysis for preparation of engineering geology maps is presented. Its use is demonstrated for an example from the city of Amsterdam, where damage to surrounding structures due to renovation of foundations of historic buildings must be kept to a minimum. Extra costs of the improved mapping procedure are soon recovered due to improved site data and optimum construction practices. 911225
Estimation of confidence bounds for mean trace length of discontinuities using scaniine surveys. Technical note Zhang Xing; Liao Guohua lnt J Rock Meeh Min Sci 1/27, N3, June 1990, P207-212 A method is presented which provides point estimation and confidence limits for mean trace length of the joints recorded on a finite size exposure. It follows the same basic sampling plan as the method of Priest and Hudson and gives the same result for point estimation, although the methods are not the same. Four case studies of its use are illustrated. 911226
Practical 3-D seafloor and sub-bottom mapping system Matthias, P K; Newton, F L Proc 22nd Annual Offshore Teclmology Conference, Houston, 7-10 May, 1990 VI, P307-313. Publ Richardson: OTC, 1990 An image processing system which can be applied to give pseudo-stereo 3D output from an integrated product of side scan sonar, bathymetry, and sub-bottom data is described. It indicates sea floor topography and geology. Applications include geologic interpretation, ROV operation, and ocean engineering.
911227
1980-90: a decade of gold exploration Clifford, J A; Meldrum, A H; Parker, R T H; Earls, G T Minerals, Materials and Industry, Proc 14th Congress of the Council of Mining and Metallurgical lmstitmions, Edinburgh, 2-6 July 1990 P323-333. Publ IMM: London, 1990 The rise in gold prices in 1979 led to exploration plans for Ireland and Scotland, where historic mining activities are documented. Reconnaissance exploration for target definition, geochemistry and geophysics of the deposits, trenching, drilling, and underground exploration are described.
Geophysical techniques See also: 911199
911228
Use of the radiomaguetotelluric technique for the inspection of pavement subgrades (In French) Chevassu, G; Grissoni, J C; LagabrieUe, R Bull Liaison Labs Pones Clmussees N166, March-April 1990. P73-82 The RMT technique allows rapid and economic examination of pavement subgrades. The pavement surface, an insulator, is transparent to electromagnetic waves. RMT reading indicates primarily the moisture content of the subgrade, from which bearing capacity may be estimated. Development of the technique and vehicle mounted equipment for continuous profiling are described. Limitations of the method are defined.
911229
Evaluation of Bristow's method for the detection of subsurface cavities Lowry, T; Shire, P N Geophysics 1/55, NS, May 1990, P514-520 Bristow's method is an electrical resistivity technique using a pole-dipole array and a simple graphical method of interpretation. Resistivity traces have been modelled over spherical and cylindrical cavities. Using a slight modification of the original interpretation technique, size and location can be determined with surprising accuracy. When geological noise is added to the simulation, maximum depth of detection is less than that reported from the field. The realism of the modelling, and field influences on the results of Bristow's method are discussed.
911230
Acoustic pulse dilfractlon by step discontinuities on a plane Zhang, Q; Jull, E V; Yedlin, M J Geophysics V55, N6, June 1990, P749-756 Diffracting edges have characteristic signatures in seismic records. These edges may indicate geological faults and are of interest in seismology. A uniform geometrical theory of diffraction is used to model acoustic pulse diffraction by step discontinuities on planar structures. Corner reflections and double diffraction, which were not included in earlier models based on Kirchoff diffraction theory, are taken into account. The improved ability to accurately and efficiently model observed behaviour is seen.
© 1991 Pergamon Press pie. Reproduction not permitted
Remote
sensing and photographic techniques
911223
Determining the age of failure of motorway earthworks from aerial survey photographs Andrews, R D Transport Road Research Laboratory Research Report N257, 1990, 22P Knowledge of earth structure working life is important for maintenance planning and design. Aerial survey photographs of MI, M4, M5, and M45 sections were examined for evidence of failures. Difficulties in recognising signs of failure are described, and uncertainty in data was taken into account in analysis. Failures were seen for a wide variety of earth materials. Cuttings showed failure rate increasing, sometimes abruptly, after several years. Embankments showed more erratic behaviour. In neither case can it be assumed that apparently stable slopes will not fail in the future. Influence of weathering of slope materials on failure merits further investigation. Raw data were of insufficient quality to attempt analysis of effects of weather on failure rates.
Structural and geotechnical mapping See also: 911140 911224
Engineering geological maps: a cost benefit analysis De Mulder, E F J Environ Geol Water Sci 1/16, NI, July/Aug 1990, P23-28 An eight-step procedure for cost-benefit analysis for preparation of engineering geology maps is presented. Its use is demonstrated for an example from the city of Amsterdam, where damage to surrounding structures due to renovation of foundations of historic buildings must be kept to a minimum. Extra costs of the improved mapping procedure are soon recovered due to improved site data and optimum construction practices. 911225
Estimation of confidence bounds for mean trace length of discontinuities using scaniine surveys. Technical note Zhang Xing; Liao Guohua lnt J Rock Meeh Min Sci 1/27, N3, June 1990, P207-212 A method is presented which provides point estimation and confidence limits for mean trace length of the joints recorded on a finite size exposure. It follows the same basic sampling plan as the method of Priest and Hudson and gives the same result for point estimation, although the methods are not the same. Four case studies of its use are illustrated. 911226
Practical 3-D seafloor and sub-bottom mapping system Matthias, P K; Newton, F L Proc 22nd Annual Offshore Teclmology Conference, Houston, 7-10 May, 1990 VI, P307-313. Publ Richardson: OTC, 1990 An image processing system which can be applied to give pseudo-stereo 3D output from an integrated product of side scan sonar, bathymetry, and sub-bottom data is described. It indicates sea floor topography and geology. Applications include geologic interpretation, ROV operation, and ocean engineering.
911227
1980-90: a decade of gold exploration Clifford, J A; Meldrum, A H; Parker, R T H; Earls, G T Minerals, Materials and Industry, Proc 14th Congress of the Council of Mining and Metallurgical lmstitmions, Edinburgh, 2-6 July 1990 P323-333. Publ IMM: London, 1990 The rise in gold prices in 1979 led to exploration plans for Ireland and Scotland, where historic mining activities are documented. Reconnaissance exploration for target definition, geochemistry and geophysics of the deposits, trenching, drilling, and underground exploration are described.
Geophysical techniques See also: 911199
911228
Use of the radiomaguetotelluric technique for the inspection of pavement subgrades (In French) Chevassu, G; Grissoni, J C; LagabrieUe, R Bull Liaison Labs Pones Clmussees N166, March-April 1990. P73-82 The RMT technique allows rapid and economic examination of pavement subgrades. The pavement surface, an insulator, is transparent to electromagnetic waves. RMT reading indicates primarily the moisture content of the subgrade, from which bearing capacity may be estimated. Development of the technique and vehicle mounted equipment for continuous profiling are described. Limitations of the method are defined.
911229
Evaluation of Bristow's method for the detection of subsurface cavities Lowry, T; Shire, P N Geophysics 1/55, NS, May 1990, P514-520 Bristow's method is an electrical resistivity technique using a pole-dipole array and a simple graphical method of interpretation. Resistivity traces have been modelled over spherical and cylindrical cavities. Using a slight modification of the original interpretation technique, size and location can be determined with surprising accuracy. When geological noise is added to the simulation, maximum depth of detection is less than that reported from the field. The realism of the modelling, and field influences on the results of Bristow's method are discussed.
911230
Acoustic pulse dilfractlon by step discontinuities on a plane Zhang, Q; Jull, E V; Yedlin, M J Geophysics V55, N6, June 1990, P749-756 Diffracting edges have characteristic signatures in seismic records. These edges may indicate geological faults and are of interest in seismology. A uniform geometrical theory of diffraction is used to model acoustic pulse diffraction by step discontinuities on planar structures. Corner reflections and double diffraction, which were not included in earlier models based on Kirchoff diffraction theory, are taken into account. The improved ability to accurately and efficiently model observed behaviour is seen.
© 1991 Pergamon Press pie. Reproduction not permitted