Nicole Metje

Site Assessment of Multiple-Sensor Approaches for Buried Utility Detection

The successful operation of buried infrastructure within urban environments is fundamental to the conservation of modern living standards. Open-cut methods are predominantly used, in preference to trenchless technology, to effect a repair, replace or install a new section of the network. This is, in part, due to the inability to determine the position of all utilities below the carriageway, making open-cut methods desirable in terms of dealing with uncertainty since the buried infrastructure is progressively exposed during excavation. However, open-cut methods damage the carriageway and disrupt societys functions. This paper describes the progress of a research project that aims to develop a multi-sensor geophysical platform that can improve the probability of complete detection of the infrastructure buried beneath the carriageway. The multi-sensor platform is being developed in conjunction with a knowledge-based system that aims to provide information on how the properties of the ground might affect the sensing technologies being deployed. The fusion of data sources (sensor data and utilities record data) is also being researched to maximize the probability of location. This paper describes the outcome of the initial phase of testing along with the development of the knowledge-based system and the fusing of data to produce utility maps.

Tunnel monitoring using multicore fibre displacement sensor

In this paper, we report the first demonstration of multiplexed fibre Bragg grating strain sensors in a multicore fibre for shape measurement and their application to structural monitoring. Sets of gratings, acting as strain gauges, are co-located in the multicore fibre such that they enable the curvature to be determined via differential strain measurement. Multiple sets of these gratings allow the curvature to be measured at several points along the fibre. In this paper, the multicore fibre is configured to measure the deflection of a simple mechanical beam arising from the displacement of concrete tunnel sections. Laboratory tests are presented in which the system was demonstrated capable of displacement measurement with a resolution of ±0.1 mm over a range of several millimetres.

Smart Pipes—Instrumented Water Pipes, Can This Be Made a Reality?

Several millions of kilometres of pipes and cables are buried beneath our streets in the UK. As they are not visible and easily accessible, the monitoring of their integrity as well as the quality of their contents is a challenge. Any information of these properties aids the utility owners in their planning and management of their maintenance regime. Traditionally, expensive and very localised sensors are used to provide irregular measurements of these properties. In order to have a complete picture of the utility network, cheaper sensors need to be investigated which would allow large numbers of small sensors to be incorporated into (or near to) the pipe leading to so-called smart pipes. This paper focuses on a novel trial where a short section of a prototype smart pipe was buried using mainly off-the-shelf sensors and communication elements. The challenges of such a burial are presented together with the limitations of the sensor system. Results from the sensors were obtained during and after burial indicating that off-the-shelf sensors can be used in a smart pipes system although further refinements are necessary in order to miniaturise these sensors. The key challenges identified were the powering of these sensors and the communication of the data to the operator using a range of different methods.

Interactions between a benthic tripod and waves on a sandy bed

In the past the amount of local disturbance to hydrodynamic and sediment processes by instrumented benthic frames has not been investigated. Here, in a series of tests on sandy beds in a large wave flume, measurements of wave-induced flows, turbulence, bedforms and suspended sediments have been obtained from the large tripod frame STABLE and from a control site away from the influence of the frame. Present measurements show surprisingly small modifications by the frame to local hydrodynamic conditions, bed morphology and vertical profiles of suspended sediment.

A portable magneto-optical trap with prospects for atom interferometry in civil engineering

The high precision and scalable technology offered by atom interferometry has the opportunity to profoundly affect gravity surveys, enabling the detection of features of either smaller size or greater depth. While such systems are already starting to enter into the commercial market, significant reductions are required in order to reach the size, weight and power of conventional devices. In this article, the potential for atom interferometry based gravimetry is assessed, suggesting that the key opportunity resides within the development of gravity gradiometry sensors to enable drastic improvements in measurement time. To push forward in realizing more compact systems, techniques have been pursued to realize a highly portable magneto-optical trap system, which represents the core package of an atom interferometry system. This can create clouds of 107 atoms within a system package of 20 l and 10 kg, consuming 80 W of power. This article is part of the themed issue ‘Quantum technology for the 21st century’.

Design and Development of a Nonintrusive Pressure Measurement System for Pipeline Monitoring

In recent years, wireless sensor network systems have increasingly been used to monitor infrastructure health. Advances in electronics and sensing systems have enabled the development of various pressure-sensing methods for pipe-pressure monitoring. This article presents laboratory-based test results as part of the development and validation of a pipeline pressure-monitoring method based on force sensitive resistors (FSR). Additionally, to validate the data, the proposed pressure-sensing method is compared with a commercially available direct-pressure sensor. Analysis of the data shows a significant correlation (correlation factor = 0.9928) between the commercial sensor and the proposed sensor. These results showed that the proposed method has an acceptable accuracy and reliability even though it is not ultimately intended for absolute-pressure measurements, but for monitoring relative pressure changes in pipes.

Seeing through the Ground: The Potential of Gravity Gradient as a Complementary Technology

In the UK there is a huge legacy of buried utility service pipelines and cables beneath our streets and new services, such as fibre optic cables, are being added all the time. Much of this utility network is poorly mapped and recorded. It is therefore important to accurately locate and map these services to aid the installation of new, and repair and maintenance of existing, assets. This will help avoid damage to adjacent services and reduce the direct and social costs associated with finding buried utilities. This paper describes two major UK initiatives—Mapping the Underworld (MTU) and Gravity Gradient Technologies and Opportunities Programme (GG-TOP)—that aim to improve the way that we locate, map, and share information on buried utility services. MTU aims to develop a multisensor device to locate buried services, while GG-TOP aims to develop gravity gradient technology to deliver a (three orders of magnitude) step change in performance.

A Stakeholder Led Accuracy Assessment System for Utility Location

In the UK alone there are many millions of miles of underground utilities and records concerning their location are often inaccurate, incomplete, or non-existent. As well as posing significant health and safety problems to construction personnel, this problem brings with it large social and financial costs. This has led to increasing use of Ground Penetrating RADAR (GPR) for utility location, but without detailed consideration of its efficacy in terms of location accuracy. Therefore, Mapping the Underworld (MTU), a multi-university research project aimed at ensuring improved accuracy in utility location, has been actively engaged in stakeholder consultation. As well as providing much useful data on stakeholder needs, this is also providing a methodology for the assessment of GPR utility location in terms of the factor of most importance to them - the degree to which the equipment provides location within their own accuracy requirements. Also, in order to provide consistency in the assessment methodology, MTU intends to construct a state-of-the-art test facility for assessing location equipment accuracy within tight tolerances. This will yield a combined methodology for reliable testing of location equipment, coupled to an accuracy assessment system weighted in a manner acceptable to stakeholders.

Mechanical reliability of optical fibre sensors and SmartRods for tunnel displacement monitoring

A novel optical fibre sensing system has been developed using fibre Bragg gratings embedded in a SmartRod structure based on pultruded composite rods. A thorough investigation of the mechanical reliability of the fibres, gratings and whole SmartRod structure was made. Techniques used included tensile testing, static fatigue in bend and dynamic fatigue in bend, in a variety of environments. The strength and interface properties of the whole structure were also tested. The mechanical reliability of the system was found to be very adequate for the proposed tunnel applications.

Mechanical reliability of optical fibre sensors for tunnel displacement monitoring

This work presents a study of the mechanical properties of optical fibre sensors based on fibre Bragg gratings for application in the in situ monitoring of displacements in tunnels. Tests were performed on fibres and gratings in both dry and humid environments. The tests encompassed both dynamic fatigue (constant stress rate) in both two-point bend and in tensile loading and static fatigue (constant stress conditions). The results indicate that the fibres and gratings are expected to have a very long lifetime under the likely mechanical and environmental conditions.