Dear Geo-Postgrad,

If you know of anyone who you think would be interested in the post below,
we would be grateful if you would bring it to her/his attention.

Thank you

Dean Millar



UNIVERSITY OF EXETER
CAMBORNE SCHOOL OF MINES

POST-GRADUATE STUDENTSHIP

CORNWALL, UK

PhD Studentship - Acoustic emission and electro-magnetic monitoring of rock
failure.

A post-graduate research studentship is available within the Geomechanics
Research Group of the Camborne School of Mines, University of Exeter in
collaboration with Rock Mechanics Technology Ltd.  Full technical details
of the project, a programme and references providing background for the
study are given below.

Interested individuals should send their CV and with a covering letter by
email, fax or post, to the address below.

Informal enquiries by telephone are also welcomed.

To find out about CSM, Cornwall and the Geomechanics Research Group visit:

http://www.ex.ac.uk/CSM

CONTACT DETAILS

Professor R.J. Pine
(Geomechanics Research Group Leader)
Camborne School of Mines
University of Exeter
Trevenson Road
Redruth
Cornwall
TR15 3SE
UK

Email:  [log in to unmask]
Tel:    +44-(0)1209-714866
Fax:    +44-(0)1209-716977


PhD Studentship - Acoustic emission and electro-magnetic monitoring of rock
failure.

Technical overview

The location of fracturing and deformation ahead of underground excavations
is important for both the understanding of failure mechanisms and
determination of appropriate reinforcement strategies / requirements.
Recent laboratory testing has indicated the potential application of
acoustic emission techniques to monitor the rock fracture process - from
initial crack formation, through fracture coalescence leading to,
ultimately, complete failure (Eberhardt et al 1999 and Stead et al 1999).
The identification, location and recording / determination of the onset of
rock fracture, both temporarily and spatially, has important implications
for excavation stability and safety purposes.  Successful recording of the
onset of fracture provides additional information for potential hazard
awareness and risk assessment for tunnelling purposes.  The concept of
crack formation and stress-induced damage has important implications for
development of damage criteria for numerical modelling purposes.

The Geomechanics Research Group at the Camborne School of Mines has
undertaken three-dimensional modelling of the effects of varying stress
fields on the stress redistribution around tunnel face-ends in coal mines
(Meyer et al 1999a and b).  This work has shown the detrimental effects of
stress magnitude concentration and tensor rotation in the immediate
vicinity of the tunnel face-end.  Combining these results with the concept
of stress damage below peak strength provides important information for the
understanding of stress-related fracturing ahead of tunnels.  The group has
also been involved with research for microseismic emission detection in Hot
Dry Rock geothermal energy development (field scale) and Kaiser effect
acoustic stress measurement (laboratory scale per Barr et al and Jupe et al
1992).   The latter work is ongoing with coal measure rocks.

The proposed studentship is to investigate the potential use of recorded
acoustic emission and electro-magnetic emission, singly or in combination,
to monitor the rock failure process in the field.  In a concurrent project
at CSM, laboratory work is being undertaken on different rock types to
characterise progressive rock damage under varying stress conditions.  This
will provide useful background and support to the proposed project.

The final aim of the proposed project, in collaboration with RMT Ltd, is to
provide the theoretical foundations and some field experiments and data for
the development of a monitoring device / system that could be used to
provide 'early warning / detection' for the onset of rock fracturing /
failure in an underground excavation.

Programme

It is envisaged that the work will commence at the beginning of the 2nd
Quarter of year 2001 and continue until the end of year 2003.  It is
envisaged that the student will be able to complete a PhD thesis a few
months later.

Initially the student will undertake a literature review on relevant
laboratory and field techniques .  The review will be guided using the
experience of the academic staff at CSM with industrial input / perspective
provided by staff of RMT.

The current laboratory work at CSM in this area will be used to assist with
training the student in the necessary experimental techniques.

The student will undergo a short period of basic underground training to
fulfil statutory requirements for UK coal mines.

As early as possible, suitable sensors (with appropriate coupling and
frequency ranges) and data logging hardware will be identified and
purchased for use in the field.  An initial experimental system will be
installed at one or more locations with the aim of monitoring background
acoustic and electro-magnetic emissions and obtaining signal waveforms from
a working (or close by) environment.   A practical objective will be to
ensure that the sensors have, as far as possible, ideal coupling with the
roof strata.  This may require, for example, the installation of bolts,
which are not an essential part of the routine roof support. A key
objective will be to identify emissions associated with rock failure,
possibly substantiated with other measurements (e.g. extensometers) and
visual observations.

Based on the data obtained from the initial experimental system(s), the
equipment may be modified or enhanced.  At this stage it is planned to
develop the data processing sufficiently that an indication of location can
be made of any detected emissions, associated with rock failure.  This will
not be a unique location but it may be possible to determine distances from
sensors.   It is envisaged that emission detection and location process
will be improved experimentally, using advice from staff at CSM, RMT and
associated researchers.

Factual progress reports will be produced at 6 month intervals, with
summaries and further interpretation in Annual reports and the Final report.

References


Barr S.P., Pine R.J. and Jupe A.J. (1992) "A study of the time dependency
of the Kaiser effect in the Carnmenellis granite, Cornwall, UK." Proc. Int.
Conf. Progress in acoustic emission, Japanese Soc. for NDT, 1992, pp 175-182.

Eberhardt E., Stead D and Stimpson B (1999). Quantifying progressive
pre-peak brittle fracture damage in rock during uniaxial compression. Int.
J. Rock mech. Min. Sci., 36, pp 361-380.

Jupe A.J., Barr S.P., and Pine R.J. (1992), "In-situ stress measurements
obtained using overcoring and the Kaiser effect of acoustic emissions
within the Carnmenellis granite Cornwall, UK." Proc. Int. Conf. Progress in
acoustic emission, Japanese Soc. for NDT, 1992, pp 167-174.

Meyer L.H.I., Stead D. and Coggan J.S. (1999). Three dimensional modelling
of the effects of high horizontal stress on underground excavation
stability. 9th ISRM Congress, Paris, 25-28 August 1999. A.A. Balkema
Publishers, pp 411-416.

Meyer L.H.I., Coggan J.S. and Stead D. (1999). Three dimensional non-linear
modelling of the effects of high horizontal stress on underground
excavation face-end stability. Vail Rocks '99. U.S. rock mechanics
symposium. June 1999, Vail, Colorado, pp 147-152.

Stead D., Eberhardt E. and Szczepanik Z. (1999). Acoustic emission studies
on stress-induced damage in sandstone. 9th ISRM Congress, Paris, 25-28
August 1999. A.A. Balkema Publishers, pp 681-685.


Dean L. Millar
Lecturer in Mining Engineering and Rock Mechanics
University of Exeter
Camborne School of Mines
Redruth
Cornwall
TR15 3SE

Tel : +44-(0)-1209-714866 x 3018
Fax: +44-(0)-1209-716977
Email : [log in to unmask]

Have you looked at the CSM Web site recently?
http://www.ex.ac.uk/CSM/