Remote pipeline assessment and condition monitoring using low-frequency axisymmetric waves: a theoretical study of torsional wave motion

Waves that propagate at low frequencies in buried pipes are of considerable interest in a variety of practical scenarios, for example leak detection, remote pipe detection, and pipeline condition assessment and monitoring. Particularly useful are the n=0, or axisymmetric, modes in which there is no displacement (or pressure) variation over the pipe cross section. Previous work has focused on two of the three axisymmetric wavetypes that can propagate: the s=1, fluid-dominated wave; and the s=2, shell-dominated wave. In this paper, the third axisymmetric wavetype, the s=0 torsional wave, is studied. Whilst there is a large body of research devoted to the study of torsional waves and their use for defect detection in pipes at ultrasonic frequencies, little is known about their behaviour and possible exploitation at lower frequencies. Here, a low-frequency analytical dispersion relationship is derived for the torsional wavenumber for a buried pipe from which both the wavespeed and wave attenuation can be obtained. How the torsional waves subsequently radiate to the ground surface is then investigated, with analytical expressions being presented for the ground surface displacement above the pipe resulting from torsional wave motion within the pipe wall. Example results are presented and, finally, how such waves might be exploited in practice is discussed.

[1]  Emiliano Rustighi,et al.  An analytical model of ground surface vibration due to axisymmetric wave motion in buried fluid-filled pipes , 2017 .

[2]  P. Cawley,et al.  The effect of complex defect profiles on the reflection of the fundamental torsional mode in pipes , 2012 .

[3]  Peter Cawley,et al.  The reflection of the fundamental torsional guided wave from multiple circular holes in pipes , 2011 .

[4]  H. V. Fuchs,et al.  Ten years of experience with leak detection by acoustic signal analysis , 1991 .

[5]  Michael J. Brennan,et al.  Wavenumber prediction of waves in buried pipes for water leak detection , 2002 .

[6]  Yoon Young Kim,et al.  High-frequency lowest torsional wave mode ultrasonic inspection using a necked pipe waveguide unit. , 2015, Ultrasonics.

[7]  Peter Cawley,et al.  The reflection of the fundamental torsional mode from pit clusters in pipes , 2012 .

[8]  Michael J. Brennan,et al.  Axisymmetric wave propagation in fluid-filled pipes: wavenumber measurements in in vacuo and buried pipes , 2004 .

[9]  Osama Hunaidi,et al.  Acoustical characteristics of leak signals in plastic water distribution pipes , 1999 .

[10]  Yan Gao,et al.  Simplified dispersion relationships for fluid-dominated axisymmetric wave motion in buried fluid-filled pipes , 2016 .

[11]  W. M. Ewing,et al.  Elastic Waves in Layered Media , 2015 .

[12]  T. K. Lockett Lamb and torsional waves and their use in flaw detection in tubes , 1973 .

[13]  A. Cohn,et al.  Site assessment of multiple sensor approaches for buried utility detection , 2011 .

[14]  Bin Wu,et al.  Circumferential and longitudinal defect detection using T(0,1) mode excited by thickness shear mode piezoelectric elements. , 2006, Ultrasonics.

[15]  A. N. Jette,et al.  Surface displacements accompanying the propagation of acoustic waves within an underground pipe , 1980 .

[16]  Peter Cawley,et al.  Investigation of guided wave propagation and attenuation in pipe buried in sand , 2015 .

[17]  Jennifer M. Muggleton,et al.  Wavenumber prediction and measurement of axisymmetric waves in buried fluid-filled pipes: Inclusion of shear coupling at a lubricated pipe/soil interface , 2013 .

[18]  Michael J. Brennan,et al.  Leak noise propagation and attenuation in submerged plastic water pipes , 2004 .

[19]  Zahari Zlatev,et al.  On the scattering of longitudinal elastic waves from axisymmetric defects in coated pipes , 2012 .

[20]  A. N. Jette,et al.  Excitation of an elastic half-space by a buried line source of conical waves , 1979 .

[21]  Emiliano Rustighi,et al.  'Mapping the Underworld': recent developments in vibro-acoustic techniques to locate buried infrastructure , 2013 .

[22]  Irene A. Stegun,et al.  Handbook of Mathematical Functions. , 1966 .

[23]  Yang Hong-dong Leak Detection Techniques and Its Evaluation of Pipeline , 2006 .

[24]  Shelley E. McDonald,et al.  Failure modes and mechanisms in gray cast iron pipe , 2001 .