| GeoMeasurements by Pulsing TDR Cables and Probes
by
Kevin O'Connor
GeoTDR, Inc. and
Professor Charles H. Dowding
Northwestern University Department of Civil Engineering
This book is available through CRC Press and Amazon.com
Table of Contents
Chapter 1. Introduction
( PDF)
Chapter 2: Basic Physics
- Pulse Testing
- Transmission Line Parameters
- TDR Reflection Type
- Resistive Terminations and the Reflection Coefficient
- Reactive Terminations
- Reactances Along Cable
- Rise Time
- Electric Field in Coaxial Cable
- Cable Geometry and Capacitance
- Measurement of Dielectric with Parallel Rods
- Propagation Velocity and Dielectric Constant
- Electric Field Distribution and Sampling Volume Around Parallel Rods
- Measurement of Conductivity with Parallel Rods
- Attenuation in Conductive Media
- Attenuation or Multiple Reflections
- Variety of TDR Waveforms
Chapter 3. Monitoring Soil Moisture
- Soil Moisture Terminology
- Probe Design
- Site-Specific Calibration Methods
- Topp's Calibration Equation - the "Yardstick"
- Calibration Coefficients for General Relationships
- Dielectric Properties and Absolute Water Content
- Influence of soil type
- Influence of soil density and shrinkage
- Influence of temperature
- Frequency considerations
- Alternative Soil Moisture Calibration Equations
Chapter 4. Field Experience and Verification of Soil Moisture Measurement
- Lysimeter and Bowen Ratio
- Neutron Probe
- Nuclear Density Moisture Gauge
- Applications and Installation Considerations
- Agriculture - irrigation control
- Landfill cover performance
- Infiltration and wetting fonts
- Soil sampling
- Road and embankment construction on expansive clay
- Freeze-thaw behavior
- Freeze-thaw pavement performance
Chapter 5. Monitoring Localized Deformation in Rock
- General Installation Considerations
- Reference crimps improve location accuracy
- Interpretation of Reflections
- Simple shearing
- Effect of shear zone width
- Simple extension
- Combined shear and extension
- Resolution and Attenuation
- Resolution
- Attentuation
- Influence of distance
- Influence of multiple deformation
- Crimp Optimization and Resolution
- Noise
Chapter 6. Field Experience and Verification of Deformation Measurement
- Comparison with Inclinometer
- Comparison with Observation Holes
- Comparison with Elastic Beam Theory
- Installation Details
- Deep holes
- Up holes (mine roof)
- Applications
- Continuous Monitoring - strata movement over active mines
- Multiplexing - strata movement over an abandoned mine
- Production well deformation - in situ sulphur mine
Chapter 7. Monitoring Soil Deformation
- Localized Shearing Deformation of Soil
- Advantages of TDR Measurement of Localized Shearing in Soil
- Required Grout and Cable Compliance
- Localized vs. General Shear
- Applications
- Highwall slope and tailings embankment
- Relative stiffness revisited
- Landslide monitoring
- Comparative Performance and Costs
- Gravel Pack Alternative
- Magnitude vs. displacement
- Low sensitivity of cable with gravel backfill
Chapter 8. Monitoring Structural Deformation
- MTDR vs. OTDR for Structural Monitoring
- Internal Structural Deformation - installation and performance
- Masonry wall on spread footing
- Reinforced concrete column
- External Structural Deformation - Installation
- Scour depth measurement during flood
- Bridge pier or abutment movement
- OTDR and Elastic Structural Deformation
- Fiber optic components of a system
- OTDR component of a system
- Other optical measurement techniques
- Measurement of stress
- Candidate fibers
- Direct transverse strain tests and embedded stress tests
- Measurement of Longitudinal Strain
Chapter 9. Air-Liquid Interfaces
- Background
- TDR reflection at the air-liquid interface
- Correction for the presence of residual water drops
- Coaxial cable offers advantages over twisted pair wire
- Applications and Case Histories
- Standpipe piezometer
- Retrofit of dam piezometer
- Water levels above and within an abandoned mine
- Water level while drilling
- Comparison with other technology
- Detection of Leaking Liquids
- Sensor cable
- Sensor String Components
- Application of leak detection
Chapter 10. Electronics
- Moisture Probes and Transmission Line Transformers
- Properties of Coaxial Cables
- Transducer Cables
- Baluns or Transmission Line Transformers
- Connectors
- Low Loss Lead Cable
- Multiplexer
- Pulser/Sampler
- Memory
- Viewing TDR Waveforms
- Computer Control or Serial Communication
- Telemetry/Cellular Data Acquisition
- Modem/Phone Line Data Acquisition
- Battery Power for Remote Monitoring
- Case History - Dam Monitoring
- Detailed Examples
- Rock deformation
- Soil moisture
- Pending Developments
Chapter 11. Software
- General Control/Acquisition Software
- SP232-Laptop Computer Control
- Acquisition settings
- Remote use
- CSI PC208 - Datalogger Control and Multiplexing
- Acquisition parameters
- Example interrogation of multiple transducer cables
- Specialized Software
- Soil Moisture - Acquire and Interpret Waveforms
- Parallel rod probes: WinTDR and PYELAB
- Segmented probes: ViewPoint
- Diode switching control
- Types of scans
- Deformation - analyze changes in raw waveforms
- NUTSA
- Waveform data formats
- Creation of scratch files and concatenation of data blocks
- Identification of waveform changes
- Quantifying waveform changes
- Storing waveforms as ASCII files
- Requirements and limitation
Appendices
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