1,721,017 research outputs found
Remote tree root mapping using a tree trunk vibration method
No full textTree roots are well known to be disruptive to underground pipe and cable networks, in particular water pipes and sewers. Damage can occur due to a number of different mechanisms: via direct penetration of the pipework resulting in leakage; through alterations in the ground water content locally, thus potentially destabilising the ground; or by means of a gradual displacing of the pipework from its original location, this possibly resulting in pipe fracture. Detecting the extent of root development of individual trees from the ground surface could therefore potentially identify areas of infrastructure which are particularly at risk from this kind of assault. ‘Mapping the Underworld’ (MTU) is an on-going research initiative that is seeking to address the consequences arising from an inability to consistently locate the buried utility service infrastructure without resorting to extensive excavations. To date, MTU has primarily focused on developing a prototype multi-sensor platform that can be used to improve the probability of detecting all buried utilities below the ground surface The technologies under investigation have included ground penetrating radar, lowfrequency quasi-static electromagnetic fields, passive magnetic fields and low-frequency vibro-acoustics. MTU has recently entered a new phase, ‘Assessing the Underworld’, in which the technologies developed thus far will be progressed to allow not only location of the buried infrastructure but remote assessment of its condition. It is within this framework that the tree vibration research described here is being undertaken. A vibrational pipe location method, which involves excitation of the pipe at some known position along with concurrent vibrational mapping of the ground surface, has been presented previously. It has been found that a simple correspondence exists between the wave propagating in the pipe and that measured on the ground surface. By examining the unwrapped phase of the vertical component of velocity measured on the ground surface, the run of the pipe can be found. This method has been modified to ascertain if the location of a tree’s roots can be similarly determined. The aim here is excite the trunk of a tree above the ground surface and then map the course of its major roots buried underground from measurements of vibration made at the ground surface. This paper presents the results of preliminary investigation
Vibrational wavenumber analysis of a fluid-filled pipe in an elastic medium for leak detection
No full textEffect of shear coupling on the axisymmetric wave motion for buried fluid-filled pipes
No full textThis paper is concerned with the effects of shear coupling at the pipe/soil interface on the ax-isymmetric wave motions for buried fluid-filled pipes. Two extreme cases are of particular interest: the "slip" condition representing lubricated contact; and the "no slip" condition representing compact contact. Dispersion relations for the w=0 axisymmetric waves are given by accounting for the fully three-dimensional effects of the surrounding soil, from which low-frequency analytical solutions to the fluid-borne s=\ wavenumber can be determined. Theoretical predictions are presented for a test MDPE water pipe buried in sandy soil for the s=\ wavenumber measurements. It is shown that the predominant effect of shear coupling at the pipe/soil interface is to add stiffness in contrast with mass loading when the shear coupling is neglected, and damping due to radiation. Comparing the two coupling cases, it is found that the real part of the wavenumber for compact contact is slightly lower than that for lubricated contact, as expected, due to the additional lateral constraint on the pipe wall. Nevertheless, the stiffness effect on the wavespeed is relatively small for both coupling cases compared with the compliance effect of the shell wall. For this particular type of soil, the attenuation for the compact coupling case is greater than for the lubricated contact case. Experimental measurements show good agreement with the predictions, and indicate that: as anticipated, for the measurement pipe, the coupling between the pipe and the soil falls between the two extremes considered
Effects of shear coupling on the acoustic characteristics of torsional waves in buried fluid-filled pipes
No full textA novel method for the remote condition assessment of buried pipelines using low-frequency axisymmetric waves
No full text“Mapping the Underworld” is a large multi-disciplinary, multi-university research programme taking place in the UK, which aims to revolutionize the way we undertake streetworks. Within this programme, a number of vibration-based techniques for remotely detecting and locating buried pipes have been developed. Relying either on the direct excitation of a pipe as it comes up to the surface or excitation of the ground in the vicinity of a buried pipe, mapping the ground surface vibration response allows information to be gathered concerning the pipe’s exact position. However, contained within this surface response is often information which could, if utilized appropriately, provide insights into the condition of the pipe as well as its location. Furthermore, critical information regarding the condition of the ground in which a pipe is buried could, in some circumstances, be gleaned. In this paper, how this additional information might be extracted, used and eventually exploited is explored. Providing the basis for work currently being undertaken in a new programme, “Assessing the Underworld”, example results are presented which demonstrate the immense potential of the proposed methods
Novel methods for the condition assessment of buried pipelines using low-frequency axisymmetric waves
No full textZero Leakage 2050, the UK’s strategic research initiative for the water industry: acoustic and vibrational methods for acoustic leak detection
No full text- …
