Distributed Fibre-optic Cable Sensing for Buried Pipe Infrastructure

在英国，长达60万公里的地下下水道系统（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，美国下水道收集系统的总重置价值在1至2万亿美元之间。仅在中国，每年就铺设4万公里的新下水管道。由于城市化和气候变化的加剧，该系统的容量需求不断增加。水务署（英国）及发达国家类似的规管机构规定水务公司有法律责任维持其污水系统的状况，并减少水浸事故的风险。因此，监察管道的堵塞情况和修补缺陷是有效管理计划的重要组成部分，以减少污水渠水浸，并优化运作和维修成本。现有的下水道调查方法仅限于解释CCTV和LightLine图像，这些图像相对较慢，并且需要带摄像机的移动手推车穿越各个下水道管道。其他现有的检测解决方案依赖于有限数量的流量计量设备（现场仪表），这些设备在下水道网络中零星地安装。因此，有明确的迹象表明，每5年对英国水网进行调查的比例不到2%，而且相当多的洪水事件要么没有报告，要么观察到的时间相当长。这阻碍了水务公司制定积极主动的维护计划，使他们能够在下水道淹水方面实现零故障。这里提出的项目是为了发展新的科学，支持新兴的光纤传感技术平台，该平台可以与机器人一起铺设在污水管道的倒立处，以感知流动状况，持续监测管道的普遍恶化，并主动响应事件。将进行理论、数值模拟和大量的实验室工作，以了解光纤电缆安全壳系统中湍流和湍流诱发振动之间的流固相互作用。光信号将被研究，数值预测和理论解释。新的信号处理和模式识别算法将被开发出来，将这些光信号与关键的流动特性和管道结构完整性的变化联系起来。此外，现场测量和验证将在主要商业合作伙伴nuron Ltd的支持下进行，使用新的光纤电缆系统。这项工作的一个关键成果将是：(i)对这项技术如何工作的新的理论理解，并朝着更高的技术准备水平发展；（ii）新的、用户友好的软件，将主要的理论发现和后处理算法结合起来，将光信号转换成沿光纤电缆长度分布测量的流特性，并为最终用户所理解。这个建议是及时的，因为它将极大地帮助我们更好地了解我们的地下基础设施的水力行为和条件，实时和前所未有的空间分辨率。新的传感器技术还将为水力学、波浪传播、结构健康/状态监测和计算流体动力学等领域提供新的理论基础。

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.