April 2010: Research Update

Posted on April 21st, 2010

The current phase of the MTU initiative aims to research and develop a multi-sensor prototype device capable of locating and mapping the position of all buried utilities.

The research is investigating four sensor technologies: ground penetrating radar (GPR), low frequency electromagnetic fields, magnetic field technologies and acoustics; their performance when deployed in combination; and how data fusion from the four sensors improves detection certainty.

Research Update

• Since the commencement of the MTU multi-sensor device project in January 2009 the focus of the research has been on sensor development and/or operational enhancement.
• Trials are planned at UK and European test sites to optimise sensor performance.

GPR

The GPR sensors are currently being developed to operate both from the surface and when contained in an ‘in-pipe’ device.  The GPR sensors will be deployed in four ways: traditional surface down; look through by transmitting from the surface with in-pipe receivers; look through by transmitting from the pipe with a surface receivers; and look out from the pipe with the transmitter and receivers both in-pipe.  Stepped frequency continuous wave protocols with orthogonal frequency division multiplexing are being used.

Low Frequency Electro-Magnetics

The low frequency electromagnetic sensor, which is based on electrical resistivity principles, has been developed from a numerical model to a proto-type and is designed to detect objects that traditional GPR surveys may miss.  It has been trialled in conjunction with a commercial GPR device, with encouraging results.

Data Acquisition

Automated data acquisition systems are currently being developed for the sensor.  A parallel PhD project has the aim of locating leaking water pipes using this sensor to detect streaming potentials.

Magnetic Field Technology

The passive magnetic field sensor has similarly developed from a numerical model to a proto-type unit that is designed to detect the magnetic fields generated from single-phase and three-phase power cables, as well as any magnetic anomalies caused by adjacent metallic pipes.  The sensor is currently being tested both under laboratory conditions in the field.

Acoustics

The surface-mounted acoustic sensors have been shown to detect clearly the location of a pipe if it is excited directly, and work is being undertaken to detect shallow pipes via excitation of the ground.  Traditional exciters are being tested in conjunction with a purpose built Rayleigh wave exciter and laser vibrometry has been trialled as a means of non-contact data collection in place of traditional geophones.

Data Fusion

Whilst the sensors are under development the team responsible for fusing the data has concentrated on developing and applying algorithms to real GPR data to permit the automatic identification of size, depth and location of buried utilities.  Once the sensors have been developed, this work will be extended to include all data from the multi-sensor device.

Device Tuning

Work is also being undertaken to identify methods to correlate the geophysical properties of the ground (essentially soil and fill materials) with its geotechnical properties in order to facilitate the development of a knowledge transfer system, based on information held in various UK databases (such as those at the British Geological Survey), that will enable the operation of the multi-sensor device to be optimised when on site.

Test Sites

Finally, designs for a UK test site are currently being developed to provide a facility where both geophysical devices could be developed and a training venue for those tasked with operating geophysical equipment in the carriageway.

Emerging Work

Three parallel projects have emanated from our work: change in geophysical response of the ground with the seasons and recent weather; impact of corroding iron pipes in clay soils on the efficacy of GPR location techniques; and acoustic responses for various soils.

VISTA: MTU Sister Project

In addition, research is being undertaken to fuse the data from the device with electronic records developed by the VISTA project (MTU’s sister project), both to improve the probability of detection and to assist in utility identification.  To further optimise the survey, the researchers are exploring how the ground conditions, and change in conditions with season, impact upon the performance of the sensors, and how geotechnical records contained in a national database can be used to optimise sensor performance on site.