School of Civil EngineeringCollege of Engineering and Physical Sciences

Monitoring the Soil and Electromagnetic (EM) Radiation

Dan Boddice and Laura Pring

Monitoring the Soil and EM RadiationOverview

Structure of this Presentation

• What are we hoping to do?

• Desk study

• Initial site investigation

• On going monitoring of the site

• Laboratory work

• Output data

Monitoring the Soil and EM RadiationOverview

What are we hoping to do?• DART is focused on improving the detection of archaeological sites

through both aerial remote sensing and geophysical techniques

• Many of these use EM radiation

• Ground penetrating radar (GPR)

• Airborne multi and hyper-spectral sensors

• Low frequency EM slingrams (e.g. EM38)

• Other techniques use magnetic or electrical properties

• Electrical resistance surveying

• Magnetometry

Monitoring the Soil and EM RadiationOverview

What are we hoping to do?

• To investigate the behaviour of EM radiation in different soil conditions

• Find ways to use the geotechnical properties of the soil to predict sensor response

• To help provide data and information to assist with the other parts of the project

Desk Study

A desk study characterises the historical and geological setting of the site.

• Historical mapping from Edina Digimap

• Geological mapping from the University of Cranfield Website

• Geological/geophysical/geochemical information from the British Geological Survey (BGS)

• Previous site investigation reports from the BGS

• Anecdotal Information from Royal Agricultural College (RAC)/landowner

• Other Sources

Monitoring the Soil and EM RadiationOverview

Monitoring the Soil and EM RadiationCirencester – Possible Monitoring Locations

Reproduced from BGS Website. Geologic Materials Copyright NERC, OS Map reproduced under licence by BGS.

Reproduced from BGS Website. Geologic Materials Copyright NERC, OS Map reproduced under licence by BGS.

Monitoring the Soil and EM RadiationHarnhill – Borehole Locations

Reproduced from BGS Website. Geologic Materials Copyright NERC, OS Map reproduced under licence by BGS.

Monitoring the Soil and EM RadiationHarnhill – Possible Well Sites

Monitoring the Soil and EM RadiationHarnhill – Geophysical Surveys

Reproduced from BGS Website. Geologic Materials Copyright NERC, OS Map reproduced under licence by BGS.

Airborne Magnetic Survey Flight Lines

Gravity Survey Points

On Site• Geological mapping of the monitoring sites and the wider area

• Geological logging of all open trenches

• Removal of undisturbed and bulk disturbed samples for laboratory testing

• In situ shear vane testing (if applicable)

• Logging of hand augered boreholes

• Possible standard penetration testing (SPT) and installation of water monitoring boreholes

• Installation of time domain reflectometer (TDR)

• Installation of weather station

Monitoring the Soil and EM RadiationOverview

Monitoring the Soil and EM RadiationOverview

Ongoing Monitoring

• TDR

• Local weather

• GPR

• Standing water (boreholes)

Monitoring the Soil and EM RadiationHow Does TDR work?

Monitoring the Soil and EM RadiationExample Data – Dielectric Permittivity

Monitoring the Soil and EM RadiationExample Data – Conductivity (Dielectric Losses)

Monitoring the Soil and EM RadiationTDR System Design

Monitoring the Soil and EM Radiation Changes to Giulio’s Design

Monitoring the Soil and EM Radiation TDR Installation

Monitoring the Soil and EM Radiation TDR Installation – Clay “Difficult” Soils

Monitoring the Soil and EM Radiation TDR Installation – “Simple” Soils

Monitoring the Soil and EM Radiation Factors which affect EM Propagation

• Soil Temperature

• Soil Moisture

• Geotechnical Properties

• Density

• Particle Size Distribution (PSD)

• Atterberg Limits

• Geochemistry

• Frequency of EM

• Magnetic components in the soil

Monitoring the Soil and EM RadiationWeather Variability over 400m

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Monitoring the Soil and EM RadiationWeather Variability over 400m

Laboratory Work

• Particle Size Distribution

• Natural Moisture Content

• Atterberg Limits (where applicable)

• Density (only possible for undisturbed samples)

• Various geochemical tests

• Testing of created soil types using a TDR probe

Monitoring the Soil and EM RadiationOverview

Monitoring the Soil and EM RadiationOutput Data

• Bulk Dielectric

• Bulk pseudo-conductivity (electrical and magnetic losses)

• Temperature and Moisture Profile of the soil and air above

• GPR survey data at different frequencies and conditions

• Geotechnical properties of the soils on site

• Local weather

• Signal propagation in varying soil conditions in the laboratory

Monitoring the Soil and EM Radiation Acknowledgments

• Giulio Curioni and Andrew Foo (Mapping the Underworld)

• Simon Price, Russell Lawley and Helen Reeves (BGS)

• Nicole Metje and David Chapman (Birmingham University)