Smart Foundations with Distributed Fibre Optics Technology

设计极限通常基于结构中的应变发展。虽然应变测量已经很成熟，但直到最近，目前的做法还仅限于通过振弦式(VWSG)或金属箔应变计以及最近使用光纤布拉格光栅(FBG)技术的光纤测量点状应变。在结构与土壤相互作用的情况下(例如，基础、隧道或管道等地下基础设施)，或者在土壤结构(道路或堤坝)的情况下，除非已知完整的原位应变状态，否则结构的状态并不完全了解。在监测桩基、隧道、管道、斜坡或路堤中的应变时，获取连续应变剖面对于精确定位局部问题区域(如接缝旋转、变形和非均匀分布的土-结构相互作用荷载)具有非常重要的价值。在这个项目中，我们计划使用一种独特的光纤技术，称为“布里渊光时域反射仪(BOTDR)”。这项新技术的新颖之处在于，可以一次检测数十公里长的光纤，以进行连续的分布式应变测量，从而提供相对廉价但高效的监测系统。该系统使用标准的低成本光纤(可能为0.1/m)，应变分辨率可达2微米应变。我们将演示分布式应变测量在监控英国和美国现场建筑地基性能方面的重要性。利用分布的应变数据，将与行业合作者一起开发一种设计工具，以优化需要修复、修复和重复使用的基础的性能。该项目得到了英国工业合作伙伴以及美国合作者(国家科学基金会和西北大学)的支持。

Design limits are frequently based on strain developing in the structure. Although strain measurement is well established, current practice has until recently been restricted to measurement of point-wise strains by means of vibrating wire (VWSG) or metal foil strain gauges and more recently by fibre optics utilising Fibre Bragg Grating (FBG) technology. Where structures interact with soil, (e.g. underground infrastructure such as foundations, tunnels or pipelines) or indeed in the case of a soil structure (road or dam embankments), the state of the structure is not fully understood unless the complete in situ strain regime is known. In the context of monitoring strain in piled foundations, tunnels, pipelines, slopes or embankments, capturing the continuous strain profile is often invaluable to pinpoint localised problem areas such as joint rotations, deformations and non-uniformly distributed soil-structure interaction loads. In this project, we propose to use a unique fibre optics technology called the 'Brillouin optical time-domain reflectometer (BOTDR)'. The novel aspect of this new technology lies in the fact that tens of kilometres of fibre can be sensed at once for continuous distributed strain measurement, providing relatively cheap but highly effective monitoring systems. The system utilizes standard low cost fibre optics (potentially 0.1/m) and the strain resolution can go down to 2 micro strains. We will demonstrate the importance of distributed strain measurements to monitor the performance of building foundations at field sites in the UK and US. Using the distributed strain data, a design tool that optimises the performance of foundations that require rehabilitation, repair and reuse will be developed with industrial collaborators. The project has supports from UK Industrial partners as well US collaborators (National Science Foundation and Northwestern University).