GPR-PrincplesProcedures&Applications.pdf
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1、 Copyright 2003 Sensors&Software Inc.03-0003-00 Ground Penetrating RadarGround Penetrating Radar Applications Principles,Procedures&Applications Principles,Procedures&A.P.AnnanA.P.Annan Copyright 2003 Sensors&Software Inc.Copies of these notes are available on CD in PDF format from Sensors&Software
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4、,Procedures&ApplicationsTable of ContentsiTable of Contents 1 Introduction.11.1What is GPR?.11.2History.31.3Current Activities&Future Developments.71.4Summary.8 2 Basic Electromagnetic Theory.92.1Overview.92.2Maxwells Equations.92.3Constitutive Equations.122.4Wave Nature of EM Fields.132.5Low Loss D
5、amped EM Wave Conditions.172.6Sinusoidally Time Varying Fields.202.7Electromagnetic Impedance.212.8Polarization.232.9EM Fields From Sources.262.10Far Field Approximation.292.11Antenna Patterns,Directivity,Gain.30 3 Physical Properties I.353.1Why are Physical Properties Important?.353.2Conduction Cur
6、rents.353.3Displacement(Polarization)Currents.373.4Total Current Flow.393.5Magnetic Permeability.403.6Complex Materials.453.7Electrical Properties of Water.503.8Real GPR Examples.523.8.1DNAPL Spill.523.8.2Conductive Contaminant.53Table of ContentsGPR Principles,Procedures&Applicationsii 4 EM Wave Pr
7、operties.554.1Wavefronts and Rays.554.2Wave Properties.554.3GPR Plateau.584.4Material Interfaces.594.5Snells Law.594.6Critical Angle.604.7Fresnel Reflection Coefficients.614.8Thin Layer Reflection.654.9Plane Wave Model for Finite Sources.684.10GPR Source Near an Interface.714.11Resolution and Zone o
8、f Influence.744.12Scattering from a Localized Object.794.13Scattering Attenuation.824.14Propagation Dispersion.84 5 GPR Instrumentation.895.1GPR Measurement Objectives.895.2Fundamental Physics.895.3GPR Timing and Resolution.925.3.1Timing .925.3.2Resolution and Bandwidth.925.4GPR Bandwidth.955.5Syste
9、m Elements&Characterization.975.6GPR Signal Acquisition.985.6.1Correlation Acquisition GPR.995.6.2Frequency Domain Mixer GPR.995.6.3Equivalent Time sampling GPR.1015.6.4Common Signal Capture Issues.1025.7Real-Time Signal Processing Fundamentals.1035.7.1Deconvolution.1035.7.2GPR Wavelet Model.1045.8S
10、ystem Performance Factor.106GPR Principles,Procedures&ApplicationsTable of Contentsiii5.9Signal Amplitude&Recording Dynamic Range.1075.9.1Characterizing System Response.1075.9.2Dynamic Range.1115.9.3Summary.1145.10Centre Frequency and Bandwidth.1155.11Antennas.1175.11.1Dipole Impulse Response or Tra
11、nsfer Function.1185.11.2Antenna Directivity.1195.11.3Shielding.122 6 Modelling of GPR Responses.1276.1The Purpose of Modelling.1276.2GPR Modelling Types&Definitions.1276.3One-dimensional(1D)Modelling.1286.3.1Radar Range Equation(RRE).1286.3.2One-Dimensional(1D)Layered Earth.1296.4Two-Dimensional(2D)
12、Modelling.1306.4.1Ray Tracing .1306.4.2FK 2D Modelling.1326.4.3Full Finite Difference(FD)Solutions .1336.4.42 D Solutions.1336.5Three-Dimensional(3D)Modelling.1336.5.13D Ray Tracing .1336.5.23D Finite Difference Modelling.1336.5.3Integral Equation Equivalent source Scattering.1356.6Inversion.136 7 S
13、urvey Design.1397.1Evaluating GPR Suitability.1397.2Reflection Survey Design.1457.2.1Selecting Operating Frequency.1467.2.2Estimating the Time Window.1487.2.3Selecting Temporal Sampling Interval.1497.2.4Selecting Station Spacing(Spatial Sampling Interval).149Table of ContentsGPR Principles,Procedure
14、s&Applicationsiv7.2.5Selecting Antenna Separation.1517.2.6Survey Grid and Coordinate System.1527.2.7Selecting Antenna Orientation.1537.3CMP/WARR Velocity Sounding Design.1547.43D Survey Design.1567.5Borehole Survey Design.156 8 Data Processing.1578.1Data Editing.1588.2Basic Processing.1598.2.1Dewow.
15、1598.2.2Time Gain.1598.2.3Temporal and Spatial Filtering.1638.2.4Discussion.1668.3Advanced Data Processing.1668.3.1Attributes.1678.3.2Deconvolution.1688.3.3Background Subtraction.1688.3.4Velocity Analysis from CMP.1698.3.5Discussion.1698.4Visual/Interpretation Processing.1708.4.1Migration.1708.4.2Ev
16、ent Picking.1718.4.3Volume Visualization.1728.5Discussion.1738.6Final Words.175 9 Interpretation,Concepts&Pitfalls.1779.1Gradational Interfaces.1779.2Velocity Determination Using Hyperbolic Fitting.1809.3Polarity.1839.4Airwave Events.1859.5X Marks the Spot.188GPR Principles,Procedures&ApplicationsTa
17、ble of Contentsv9.6Plastic Water Pipe Diameter Determination.1909.7Antenna Shielding.1939.8Ringing on Radar Records.1969.9GPR Time Zero&Depth Estimates.2009.10GPR Antenna Elevation.2029.11Determining Layer Thickness&Velocity from CMP Data.2059.11.1Analysis Procedure.2059.11.2Intercept Time&RMS Veloc
18、ity Conversion to Depth&Interval Velocity .2099.11.3Direct Air Wave&Ground Wave .2109.11.4Summary.2109.12CMP Analysis.211 10 Case Studies.21310.1Mining&Quarrying.21310.2Geotechnical&Environmental.21810.3Forensic&Archeology.23110.4Buried Utilities.24010.5Structure Assessment(NDT).24510.6Military,Law
19、Enforcement&Espionage.26210.7Bio Applications.26310.8Snow&Ice.26410.9Educational material.269 11 References.271Table of ContentsGPR Principles,Procedures&ApplicationsviGPR Principles,Procedures&Applications1-Introduction1 1INTRODUCTIONGround penetrating radar(GPR)is a relatively new geophysical tech
20、nique.The last decade has seen major advancesas the technology matures.The history of GPR is intertwined with the diverse applications of the technique.GPR hasthe most extensive set of applications of any geophysical technique leading to a wide range of application spatialscales and concomitant dive
21、rsity of instrument configurations.This document is intended to introduce the physical principles underpinning GPR and provide practical guidance tousers of the method.1.1WHAT IS GPR?Before delving into the history,GPR needs definition.GPR uses electromagnetic fields to probe lossy dielectric mate-r
22、ials to detect structures and changes in material properties within the materials(Davis&Annan(1989).Reflectionand transmission measurements,as depicted in Figure 1-1,are employed.Most applications to date have been in nat-ural geologic materials,but widespread use also occurs for man-made composites
23、 such as concrete,asphalt and otherconstruction materials.In lossy dielectric materials,electromagnetic fields can penetrate to a limited depth beforebeing absorbed.Hence,penetration is always an issue.With GPR,the electromagnetic fields propagate as essentially non-dispersive waves.The signal emitt
24、ed travelsthrough the material,is scattered and/or reflected by changes in impedance giving rise to events which appear similarto the emitted signal.In other words,signal recognition is simple because the return signal looks like the emitted sig-nal.Figure 1-2 depicts the general nature of GPR refle
25、ction profiling.Figure 1-3 shows the GPR response of two roadtunnels.GPR field behavior occurs over a finite frequency range generally referred to as the GPR plateau where velocity andattenuation are almost frequency independent.The GPR plateau usually occurs in the 1 MHz to 1000 MHz frequencyrange.
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