www.assessingtheunderworld.org

Assessing The Underworld

An Integrated Performance Model of City Infrastructures

Work Stream 2: Vibro-acoustics

Dr Jen Muggleton, Dr Emiliano RustighiInstitute of Sound & Vibration Research, University of Southampton

jmm@isvr.soton.ac.uk, er@isvr.soton.ac.uk

Objectives• To use a pipe vibration method to assess the condition of buried pipework

• To investigate a variety of ground excitation methods to interrogate both the ground and the buried infrastructure

• To explore a tree excitation method to determine the location of tree roots, to identify areas of pipe network at risk of damage

• To develop vibro-acoustic methods to measure relevant wavespeeds (including variation with depth) in situ

• To examine the potential of adopting an in-pipe excitation method to assess pipe condition

Journal Papers

Road and Soil Characterization

• Modelling & experimental work has been undertaken to

• Develop methods to determine soil elastic properties

in situ

• Detect and locate cracks in road/pavement surfaces

• In particular

• A range of soil excitation methods to excite different

wavetypes examined

• Combining vertical & horizontal ground vibration

responses to increase resolution and accuracy of

spectral images

• Information gleaned from electromagnetic & seismic

methods compared

• Wave decomposition method for crack detection

investigated

• Use of inversion methods to extract near-surface

wavespeed information in both homogenous soil

and layered ground carried out

• Different source-to-asphalt couplings examined

Geophone arrangement for crack interrogation

Example results from numerical study for crack detection

1. J M Muggleton, M K Kalkowski, Y Gao and E Rustighi, A theoretical study of the fundamental torsional wave in buried pipes for pipeline condition assessment and monitoring, Journal of Sound & Vibration 374, (2016), 155-171.

2. Y Gao, F Sui, J M Muggleton, J Yang, Simplified dispersion relationships for fluid-dominated axisymmetric wave motion in buried fluid-filled pipes, Journal of Sound & Vibration 375, (2016), 386-402.

3. Y Gao, Y Liu, J M. Muggleton, Axisymmetric fluid-dominated wave in fluid-filled plastic pipes: Loading effects of surrounding elastic medium . Applied Acoustics 116, 43–49, (2017)

4. M K Kalkowski, J M Muggleton and E Rustighi, An experimental approach for the determination of axial and flexural wavenumbers in circular exponentially tapered bars. Journal of Sound & Vibration 90, (2017), Pages 67-85

5. Y Gao, F Sui, X Cheng, J Yang, J M Muggleton and E Rustighi, A model of ground surface vibration due to axisymmetric wave motion in buried fluid-filled pipes. Journal of Sound and Vibration, 395, (2017),142-159

6. Michał K. Kalkowski, Jennifer M. Muggleton, Emiliano Rustighi, Axisymmetric semi-analytical finite elements for modelling waves in buried/submerged fluid-filled waveguides. Accepted for publication in Computers & Structures, 196, (2018), 327-340

7. M Iodice, J Muggleton and E Rustighi, The Synergetic Use of Two Seismic Spectral Methods for the Detection of Surface-Breaking Cracks in Asphalt. Under review Journal of Sound and Vibration, 2018

8. M Iodice, J Muggleton and E Rustighi, The Detection of Surface-Breaking Cracks in Asphalt Using the Wave Decomposition Method. Under review Journal of Non-destructive Evaluation, 2018

9. M.J. Brennan, M. Karimi, J.M. Muggleton, F.C.L Almeida, F. Kroll de Lima, P.C. Ayala, D. Obata, A.T. Paschoalini, N. Kessissoglou, On the Effects of Soil Properties on Leak Noise Propagation in Plastic Water Distribution Pipes. Under review, Journal of Sound and Vibration, 2018

Tree Excitation Method

• Wave energy travels from the trunk excitation location down to the

underground root network

• Vibrating roots excite waves in soil which, measured at the ground surface,

can be used to estimate their location and extent

• Within WS2 we studied wave propagation in exponentially tapered rods, to

understand the phenomena expected in real tree roots and explore the ways

waves can be used to estimate root extent and depth.

free flexuralfree axial

A purpose-built root model used in laboratory experiments (measuring waves)

buried root

axial waves

Instrumented root model buried in the sandbox –

experimental results below

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response

(axial

excitation)

Finite element method results

root response

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Current work: (1) assessing the effect of

soil pressure on waves in the root (lab);

(2) experiments on the root model buried in

the ground (field test site)

In-Pipe Excitation

Shear Wave Excitation: Signal Processing

• A novel Near-Surface wave estimation technique via focusing of the

array on the surface

• Use of Dual-Apodisation and other array signal-processing techniques

Simulated

Measured

DATA Cross - CorrelationBasic

SCOT

PHAT

Segment averaging

Bandpass filter

Enveloping

Normalisation

Data processing

Spatial filter

Enveloping

Image scale

Imaging Technique

StackingDual - Apodization

DAX; PCF; SCF

Enveloping Final image

Image processing

• Use of deconvolution techniques: CLEANORIGINAL

0 1 2 3 4 5 6

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• Field measurements shows that tree roots leave

a distinct signature on ground surface vibration

responses when the trunk is excited.

Field installation: (a) inhomogeneous structure of the soil and

root installation; (b) trunk attachment; (c) shaker on the trunk;

(c) ground surface sensors.

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• In-pipe excitation by underwater loudspeaker

• Comparable with structural pipe excitation

• Other means of excitation under consideration

Uniform Stacking

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Apodized Stacking

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Phase Coherence Imaging

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Sign Coherence Imaging

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Coherence Factor Map

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Pipe Excitation Technique

• Waves propagating along

pipe will radiate to the

ground surface

• Axial dependence of waves

in pipe mirrored in ground

surface response

pipe end

32mm hole

Magnitude and phase of ground surface response above an

MDPE pipe laid under grass

0 5 10 15 20 25-0.7

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least squares fit (373m/s)

end of pipe

Ground surface response: unwrapped phase

gradients directly above an MDPE water pipe

Magnitude of ground surface response

above a pipe laid in mixed ground with

distinct boundaries

• Reflections from discontinuities in pipe

(holes/cracks) will manifest as subtle

changes in ground surface response

• Changes in the soil will also affect ground

surface response, with rapid changes

resulting in wave reflections and

corresponding peaks in magnitude

Torsional Motion• Torsional motion may be linked to certain types of

pipe failure, in particular spiral fracture of cast iron

pipes

• Ultrasonic inspection techniques frequently exploit

torsional waves but little is known about their

behaviour at audio frequencies

• Modelling work has been undertaken to predict

• dispersion characteristics (wavespeed &

attenuation) for buried cast iron/plastic pipes

• ground surface response as a result of torsional

wave motion in pipe

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• the in-vacuo torsional wavenumber, kT;• a pipe wall mass component, ω2ρph;• a soil shear stiffness component, μm/a;• and a shear wave radiation component

associated with the Hankelfunction ratio,

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