atu’s advances in vibroacoustics
TRANSCRIPT
ATU’s Advances in Vibroacoustics
Emiliano RustighiJen 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 0 2 4 6-6
-4
-2
0
2
4
6
8
-10
-5
0
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)
Axia
l d
ista
nce a
lon
g p
ipe, x(m
)
-2 0 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 or 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)
Ax
ial
ran
ge
(m
)
-2 0 20
2
4
6
8
10
12
-30
-25
-20
-15
-10
-5
0
change in soil type
5
In-Pipe Excitation
• Recent change in UK legislation
• Local excitation/assessment
• Source Localisation: Techniques well developed
6
We have nowproven that we canuse surface responseto assess pipes
We can now acoustically
excite a pipe from inside
Apodization: comi Type: DAX
0 1 2 3 4 5 6
Horizontal Position (m)
0
0.5
1
1.5
2
De
pth
(m)
• Array of sensors focused on the surface only
• Max in std
Near-surface wavespeed estimation
DA Signal Processing
Phase Coherence Imaging
0 1 2 3 4 5 6
Horizontal Position (m)
0
0.5
1
1.5
2
De
pt h
(m)
0
0.5
1
Sign Coherence Imaging
0 1 2 3 4 5 6
Horizontal Position (m)
0
0.5
1
1.5
2
De
pt h
(m)
0
0.5
1
Coherence Factor Map
0 1 2 3 4 5 6
Horizontal Position (m)
0
0.5
1
1.5
2
De
pt h
(m)
0
0.5
1
Istantaneous Phase Weight
0 1 2 3 4 5 6
Horizontal Position (m)
0
0.5
1
1.5
2
De
pt h
(m)
0
0.5
1
Uniform Stacking
0 1 2 3 4 5 6
Horizontal Position (m)
0
0.5
1
1.5
2
De
pt h
(m)
0
0.5
1
Apodized Stacking
0 1 2 3 4 5 6
Horizontal Position (m)
0
0.5
1
1.5
2
Dep
t h(m
)
0
0.5
1
9
We can now automaticallydetect near-surfacewavespeed
We have now reduced data analysis time andinterpretation time
notch.
Crack Detection I
• MASW/MISW 𝑓-𝑘 spectra: MISW adds a fictitious periodicity which manifests in the spectral image
• Extract information regarding location and depth of the cracking.
MISWMASW
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 of 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 locatea buried root