ATUs Advances in Vibroacoustics Emiliano Rustighi Jen Muggleton - - PowerPoint PPT Presentation

ATU’s Advances in Vibroacoustics

Emiliano Rustighi Jen Muggleton

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 in order to identify areas of pipe network at risk of damage

2

Pipe Excitation method: Background

• When pipe is excited, wave propagation in the pipe

mirrored at the ground surface and the run of the pipe can be determined from ground vibration contours

35Hz

• 6
• 4
• 2

2 4 6

• 6
• 4
• 2

2 4 6 8

• 10
• 5

5 10

Soil wavespeed Pipe wavespeed

Phase of ground surface response above an MDPE pipe laid under grass

3

Pipe excitation: Detection of holes and cracks

Lateral distance from pipe, y(m) Axial distance along pipe, x(m)

• 2

2 2 4 6 8 10 12 14 16 18 20

• 60
• 55
• 50
• 45
• 40
• 35
• 30
• 25
• 20

pipe end 32mm hole

• Reflections from

discontinuities in pipe (bends, holes, cracks) will manifest as more

• r less subtle changes

in ground surface response

• Monitor changes over

time

Magnitude of ground surface response above an MDPE pipe laid under grass

4

Pipe excitation: Assessing soil condition

• Changes in the soil will also

affect ground surface response: wave reflections = peaks in magnitude

• Interactions between ground

and buried infrastructure are complex

19Hz Lateral distance from excitation location (m) Axial range (m)

• 2

2 2 4 6 8 10 12

• 30
• 25
• 20
• 15
• 10
• 5

change in soil type

5

In-Pipe Excitation

• Recent change in UK legislation
• Local excitation/assessment
• Source Localisation: Techniques well developed

6

We have now proven that we can use surface response to assess pipes We can now acoustically excite a pipe from inside

Apodization: comi Type: DAX

1 2 3 4 5 6

Horizontal Position (m)

0.5 1 1.5 2

Depth (m)

• Array of sensors

focused on the surface only

• Max in std

Near-surface wavespeed estimation

DA Signal Processing

Phase Coherence Imaging

1 2 3 4 5 6

Horizontal Position (m)

0.5 1 1.5 2

Depth (m)

0.5 1

Sign Coherence Imaging

1 2 3 4 5 6

Horizontal Position (m)

0.5 1 1.5 2

Depth (m)

0.5 1

Coherence Factor Map

1 2 3 4 5 6

Horizontal Position (m)

0.5 1 1.5 2

Depth (m)

0.5 1

Istantaneous Phase Weight

1 2 3 4 5 6

Horizontal Position (m)

0.5 1 1.5 2

Depth (m)

0.5 1

Uniform Stacking

1 2 3 4 5 6

Horizontal Position (m)

0.5 1 1.5 2

Depth (m)

0.5 1

Apodized Stacking

1 2 3 4 5 6

Horizontal Position (m)

0.5 1 1.5 2

Depth (m)

0.5 1

9

We can now automatically detect near-surface wavespeed We have now reduced data analysis time and interpretation time

Crack Detection I

• MASW/MISW 𝑔-𝑙 spectra: MISW adds

a fictitious periodicity which manifests in the spectral image

• Extract information regarding location

and depth of the cracking.

MISW MASW

11

Crack Detection II

• Use of wave decomposition method: direct and reflected

waves amplitudes and phase

• The resonances of the reflection coefficient and the cut-offs
• f the transmission coefficient are associated with the

depth of the crack.

• The phase of the direct and of the reflected wave gives an

indication of the location of the crack with respect to the reference point.

12

We can now assess crack presence from MISW/MASW We can now locate and characterise cracks from reflections

Buried Tree Root Lab Experiment

• Simulated root embedded in sand

– Experiments and Numerical models – Flexural & axial waves studied – Work to date shows that roots can potentially be detected at ground surface using this method

Instrumented root model buried in the sandbox

14

ground response (axial excitation)

Tree Root Mapping: Field Experiments

• Simulated Root buried at UoS

15

Tree Root Mapping: Field Experiments

• Simulated Root buried at UoS
• Distinct signature on ground

surface vibration responses

16

We can now locate a buried root