Distributed Fibre-optic Cable Sensing for Buried Pipe Infrastructure

在英国，60万公里长的地下下水道系统(包括私人下水道)正在老化，而且监管不力。在欧洲大陆，下水道资产的总价值达到2万亿欧元。美国环保署估计，美国的下水道收集系统的总替换价值在1万亿至2万亿美元之间。仅中国一地，每年就新铺设下水道4万公里。由于日益加剧的城市化和气候变化，该系统面临着日益增长的产能需求。Ofwat(英国)和发达国家的类似监管机构对水务公司施加法律责任，以维护其下水道系统的状况，并减少发生洪水事件的风险。因此，监测管道的堵塞和缺陷修复是有效管理计划的重要组成部分，以减少污水泛滥并优化运营和维护成本。现有的下水道测量方法仅限于解释CCTV和LightLine图像，这些图像相对较慢，需要带摄像头的移动手推车才能穿过单独的下水道管道。其他现有的检查解决方案依赖于数量有限的流量测量设备(现场流量计)，这些设备分散安装在整个下水道网络中。因此，有明确的迹象表明，每5年调查一次的英国网络不到2%，相当数量的洪水事件要么没有报告，要么观察到了相当长的延迟。这妨碍了自来水公司制定一项积极主动的维护方案，使它们能够在下水道泛滥方面实现零故障。本文提出的项目是为了发展新的科学，以支持新兴的光纤传感技术平台，该平台可以在下水道管道的内侧铺设机器人，以感知流动状况，并连续无处不在地监测管道的劣化，并主动对事件做出反应。我们将进行理论、数值模拟和广泛的实验室工作，以了解光纤电缆密封系统中湍流和湍流诱发振动之间的流体-结构相互作用。将对光信号进行研究、数值预测和理论解释。将开发新的信号处理和模式识别算法，以将这些光信号与关键流动特性以及管道结构完整性的任何变化联系起来。此外，将在主要商业合作伙伴Nuron有限公司的支持下，使用新的光纤电缆系统进行现场测量和验证。这项工作的一个主要成果将是：(1)对这项技术如何工作有新的理论理解，并朝着更高的技术准备水平发展；(2)新的用户友好的软件，它将纳入主要的理论发现和后处理算法，将光信号转换为沿光纤电缆长度分布测量并为最终用户所理解的流动特性。这项提议是及时的，因为它将大大有助于我们需要更好地实时和以前所未有的空间分辨率了解我们埋藏的基础设施的水力行为和状况。新的传感器技术还将在水力学、波传播、结构健康/状态监测和计算流体动力学领域发展新的理论基础。

In the UK the 600,000 km long underground sewer system (including private sewers) is ageing and poorly monitored. In continental Europe, the total value of the sewer assets amounts to 2 trillion Euros. The US EPA estimates that sewer collection systems in the USA have a total replacement value between $1 and $2 trillion. In China alone 40,000 km of new sewer pipes are laid every year. The system is subject to increasing capacity demands because of increased urbanisation and climate change. OFWAT (UK) and similar regulatory bodies in the developed countries impose a legal duty on water utilities to maintain the conditions of their sewer systems and to reduce the risk of flooding incidents. Consequently, monitoring pipes for obstructions and defects remediation forms an important part of an effective management programme to reduce sewer flooding and optimise the operational and maintenance costs. Existing sewer survey methods are limited to the interpretation of CCTV and LightLine images which are relatively slow and require a mobile trolley with camera to traverse through individual sewer pipes. Other existing inspection solutions rely on a limited number of flow metering devices (spot meters) which are installed sparsely across the sewer network. As a result, there are clear indications that less than 2% of the UK network is surveyed every 5 years and that a considerable number of flooding incidents are either unreported or observed with a considerable delay. This prevents the water utilities from developing a proactive maintenance programme which would enable them to achieve zero-failures in terms of sewer flooding. The project proposed here is formulated to develop new science which underpins the emerging fibre-optic sensing technology platform which can be laid with a robot in the invert of a sewer pipe to sense the flow conditions and continuously monitor pipe deterioration pervasively and to respond to events proactively. Theoretical, numerical modelling and extensive laboratory work will be carried out to understand the fluid-structure interactions between the turbulent flow and turbulence-induced vibration in the fibre cable containment system. The optical signals will be studied, numerically predicted and theoretically explained. New signal processing and pattern recognition algorithms will be developed to link these optical signals to key flow characteristics and to the change in any change structural integrity of the pipe. In addition, field measurements and validation will be carried out with support the lead commercial partner, nuron Ltd, using the new fibre-optic cable system. A key outcome of this work will be: (i) new theoretical understanding how this technology works and be developed towards a much higher technology readiness level; (ii) new, user-friendly software which will incorporate the major theoretical findings and post-processing algorithms that convert the optical signal to the flow characteristics measured distributively along the fibre-optic cable length and understood by the end-user. The proposal is timely because it will contribute significantly to the need for us to better understand the hydraulic behaviour and conditions of our buried infrastructure in real time and at an unprecedented spatial resolution. The new sensor technology will also enable new theoretical foundations to be developed in the areas of hydraulics, wave propagation, structural health/condition monifoting and computational fluid dynamics.