Fiber optic monitoring of an anti-slide pile in a retrogressive landslide

Anti-slide piles are one of the most important reinforcement structures against landslides,and evalu-ating the working conditions is of great significance for landslide mitigation.The widely adopted analytical methods of pile internal forces include cantilever beam method and elastic foundation beam method.However,due to many assumptions involved in calculation,the analytical models cannot be fully applicable to complex site situations,e.g.landslides with multi-sliding surfaces and pile-soil interface separation as discussed herein.In view of this,the combination of distributed fiber optic sensing(DFOS)and strain-internal force conversion methods was proposed to evaluate the working conditions of an anti-sliding pile in a typical retrogressive landslide in the Three Gorges reservoir area,China.Brillouin optical time domain reflectometry(BOTDR)was utilized to monitor the strain distri-bution along the pile.Next,by analyzing the relative deformation between the pile and its adjacent inclinometer,the pile-soil interface separation was profiled.Finally,the internal forces of the anti-slide pile were derived based on the strain-internal force conversion method.According to the ratio of calculated internal forces to the design values,the working conditions of the anti-slide pile could be evaluated.The results demonstrated that the proposed method could reveal the deformation pattern of the anti-slide pile system,and can quantitatively evaluate its working conditions.

Distributed fiber optic sensors for tunnel monitoring:A state-of-the-art review

Distributed fiber optic sensors(DFOSs)possess the capability to measure strain and temperature variations over long distances,demonstrating outstanding potential for monitoring underground infrastructure.This study presents a state-of-the-art review of the DFOS applications for monitoring and assessing the deformation behavior of typical tunnel infrastructure,including bored tunnels,conventional tunnels,as well as immersed and cut-and-cover tunnels.DFOS systems based on Brillouin and Rayleigh scattering principles are both considered.When implementing DFOS monitoring,the fiber optic cable can be primarily installed along transverse and longitudinal directions to(1)measure distributed strains by continuously adhering the fiber to the structure’s surface or embedding it in the lining,or(2)measure point displacements by spot-anchoring it on the lining surface.There are four critical aspects of DFOS monitoring,including proper selection of the sensing fiber,selection of the measuring principle for the specific application,design of an effective sensor layout,and establishment of robust field sensor instrumentation.These four issues are comprehensively discussed,and practical suggestions are provided for the implementation of DFOS in tunnel infrastructure monitoring.

About Some Aspects of Use of Optical Sensors for Monitoring the Aquatic Environment

Multi-channel polarization optical technology is increasingly used for prompt monitoring of water systems.Optical devices during the assessment of water quality determine the intensity of light through the studied aquatic environment.Spectrophotometric devices measure the spectrum of weakening of light through the aquatic environment.Spectroellipsometric devices receive spectra in vertical and horizontal polarizations.The presented article develops an adaptive optical hardware and image system for monitoring water bodies.The system is combined.It consists of 2 parts:1)automated spectrophotometer-refractometer,and 2)adaptive spectroellipsometer.The system is equipped with a corresponding algorithmic and software,including algorithms for identifying spectral curves,databases and knowledge of spectral curves algorithms for solving reverse problems.The presented system is original since it differs from modern foreign systems by a new method of spectrophotometric and spectroellipsometric measurements,an original elemental base of polarization optics and a comprehensive mathematical approach to assessing the quality of a water body.There are no rotating polarization elements in the system.Therefore,this makes it possible to increase the signal-to-noise ratio and,as a result,improve measurement stability and simplify multichannel spectrophotometers and spectroellipsometers.The proposed system can be used in various water systems where it is necessary to assess water quality or identify the presence of a certain set of chemical elements.

Optical Label-Based Cost-Effective DWDM Optical Network Performance Monitoring Using Low-Bandwidth PD with Novel SRS Mitigation DSP

Large-scale dense wavelength division multiplexing(DWDM)multi-channel performance monitoring is one of the indispensable technologies for the flexible optical networks.The existing Labelbased monitoring scheme requires expensive optical demultiplexing components/equipment to avoid the influence of stimulated Raman scattering(SRS),which is not only costly and bulky,but also could not monitor the wavelength channels simultaneously.In this paper,a low-cost,high-accuracy monitoring scheme based on Optical Label Method is proposed for DWDM networks,where the optical channel power and node identification(ID),as the main monitoring targets that both can indicate or evaluate the channel connection status,could be efficiently monitored.In the scheme,a novel digital signal processing(DSP)method of SRS mitigation is proposed and demonstrated,and an asynchronous code-division multiple access(A-CDMA)based digital label encoding and decoding method is adopted to distinguish the node ID so that channel initial added node can be accurately verified,thereby wavelength connection status can be reliably monitored by combining the channel power and node ID information.The simulation results show that each wavelength channel power and node ID can be accurately monitored only by low bandwidth photoelectric detector(PD)under the condition of 80 wavelengths and 10 spans at C-band.

Feasibility study on sinkhole monitoring with fiber optic strain sensing nerves

Anthropogenic activity-induced sinkholes pose a serious threat to building safety and human life nowadays.Real-time detection and early warning of sinkhole formation are a key and urgent problem in urban areas.This paper presents an experimental study to evaluate the feasibility of fiber optic strain sensing nerves in sinkhole monitoring.Combining the artificial neural network(ANN)and particle image velocimetry(PIV)techniques,a series of model tests have been performed to explore the relationship between strain measurements and sinkhole development and to establish a conversion model from strain data to ground settlements.It is demonstrated that the failure mechanism of the soil above the sinkhole developed from a triangle failure plane to a vertical failure plane with increasing collapse volume.Meanwhile,the soil-embedded fiber optic strain sensing nerves allowed deformation monitoring of the ground soil in real time.Furthermore,the characteristics of the measured strain profiles indicate the locations of sinkholes and the associated shear bands.Based on the strain data,the ANN model predicts the ground settlement well.Additionally,micro-anchored fiber optic cables have been proven to increase the soil-to-fiber strain transfer efficiency for large deformation monitoring of ground collapse.

煤层采动巨厚松散层全断面监测及内部变形特征

开采沉陷是煤炭资源井工开发利用所面临的主要环境地质问题,尤其对于我国东部高潜水位矿区而言,巨厚松散层的移动变形控制与采动减损评价备受关注。为了研究巨厚松散层内部移动机制,明确其对地表移动变形影响,以淮南新集矿区某井田为研究区,通过采用分布式光纤与并行电法联合测试技术,构建超过600 m深度全断面钻孔监测系统,探究巨厚松散层变形特征和内部移动规律。全断面监测系统能够获取煤层采动区域巨厚松散层内部应变、位移信息及监测钻孔周围电阻率变化情况,量化地层监测断面松散层内部移动变形时空关系和渗流场变化数据,分析松散层内地层变形特征与发育形态。研究结果表明:多参量联合测试技术的应用,显著提高了对巨厚松散层移动变形的监测效率和变形定位的准确性,获得了工作面回采位置与松散层内部变形时空演变关系。并根据松散层变形特征,将采动影响过程划分为超前影响期、弱采动影响期、强采动影响期、采后沉稳期4个阶段,揭示了超前影响变形表现“台阶状”形态与采动影响期的“反向3字型”移动特征,同时分析了“反向3字型”移动模式的构成条件、影响因素。基于全断面监测数据,提出巨厚松散层变形多场可测信息量化评价方法,阐明了巨厚松散层在煤层开采过程中存在分层应力积累与释放的规律。研究内容为巨厚松散层内部移动变形的精细化监测分析提供重要的技术支持。全断面监测技术的应用,也可为采动损害过程监测与评价、矿山生态源头减损与减沉、沉陷区土地规划与复垦以及松散层内注浆改造等提供参考。

基于多时相光学遥感影像亚像素相关的边坡监测——以溪洛渡电站为例

水电站高边坡监测是水电站灾害防治中的关键问题,基于卫星遥感技术进行库区滑坡监测是解决该问题的重要手段之一。利用卫星影像亚像素相关性算法获取地表形变位移场,能够克服SAR影像失相关因素,在水电站边坡监测中具有重大的应用潜力。本文以溪洛渡电站2015-2019年5期Google Earth影像和2019-2022年4期Sentinel-2影像为数据源,采用相位相关算法计算了边坡形变量,通过构建一次多项式曲面拟合模型去除轨道误差等趋势性误差,获取了2016、2017和2019年溪洛渡电站下游边坡形变值。分析显示,两种影像提取得到的边坡形变量具有相同的变化趋势,均与谷幅实测数据吻合较好。本文结果验证了基于多时相遥感数据将亚像素相关性匹配技术运用于大型水电站边坡形变监测的可行性。

星载激光雷达视轴监测系统设计

提出了一种针对星载激光雷达在轨高精度光轴监测与标定需求的多光轴监测方法,该方法基于主动激光光源。通过使用785 nm的激光,分束后分别照射到星敏感器的基准棱镜和接收望远镜的取光棱镜,反射信号被聚焦至监视相机的焦平面,实现了对接收光轴及星敏光轴的精确监测。此外,监视相机还同步采集发射激光的部分能量,用于测量监测发射光轴。文中详细描述了光学系统的设计流程及关键组件的优化方案,并通过地面真空环境试验及在轨监测数据进行了验证。设计结果表明,各监视通道的成像质量达到了衍射极限,收发光轴的设计精度分别为0.09μrad和2.28μrad,关键组件取光棱镜的温控精度达到了±0.2℃。地面的真空热光试验结果进一步验证了该方案的高精度光轴监视能力,收发光轴的监测精度均优于3μrad。最后通过分析激光雷达入轨后的测量数据,确认了视轴监测系统的工作稳定性,成功实现了在轨的高精度光轴监视。该研究成果为星载激光雷达提供了一种有效的在轨高精度光轴监测与标定解决方案。

堤防光纤感知系统建立与汛期应急监控

汛期堤防安全关系到人民的生命和财产安危与社会稳定,而不断提高汛期堤防应急监控水平是减轻洪涝灾害的必然途径。本文对现有堤防的相关监测技术进行了评述,在此基础上,结合作者20余年在地质与岩土工程光纤监测理论研究、技术研发和堤防监控应用实践,梳理了汛期堤防的应急光纤监控内容;介绍了基于3Ds的分布式光纤感测技术的堤防监控原理与最新进展;构建了汛期堤防应急光纤感知系统;重点介绍了汛期堤防水位、渗流、侵蚀和形变等分布式光纤监控技术,并指出了今后的研发方向和目标,以期为我国的汛期堤防应急防控提供一个新的监控思路与技术手段。

基于光纤传感技术的工程监测应用研究

光纤传感技术作为当前热门技术之一,在工程监测领域有着许多重要应用。通过探讨光纤传感技术在工程形变监测中的应用案例,展示了其在工程监测领域的重要性。光纤传感技术利用光纤作为传感元件,可以实现对形变的连续、实时监测,并提供高精度的监测数据。通过布设应变光缆和温度补偿光缆,在合璧津高速公路K134段高架桥上进行了监测实验。结果表明,光纤传感技术能够准确评估结构的变形情况,并通过温度补偿算法消除了温度变化对数据的影响。通过几何方法计算沉降位移,可以实现对沉降位移的估算。

基于多模光学信号的火灾监测系统设计

该文针对传统火灾监测系统适用场景单一、预警反应较慢等缺点,提出一种集成红外、紫外、可见光等多模光学信号的火灾监测技术,实现对明火、高温、烟雾等险情的快速识别。在该基础上设计一套完整的火灾监测系统,实现对火灾数据的监测、存储、报警,极大地丰富火灾监测系统的适用场景,缩短系统响应时间,提高系统的可靠性。

结构健康监测系统在木结构古建筑中的应用

文物木结构古建筑是一个国家文化的重要组成部分,代表着民族文化的自信与传承。然而由于长时间受到环境和人为侵蚀,木结构古建筑易遭到损坏。为更好地保存好木结构古建筑以及其代表的文化内涵,对其结构安全监测提出了迫切的需求,近年来对木结构古建筑的安全监测方法也得到了快速的发展。分别介绍了虚拟重建、红外热成像、地面激光雷达、超声波监测、光纤传感等技术的原理及在木结构古建筑监测中的应用,并总结了其各自的优势与劣势。针对木结构古建筑采光不足问题,总结了光导系统,尤其是光纤光导照明系统对自然光的引入,该类照明系统具有清洁、安全的特点,避免了烛火、电类照明系统为木结构古建筑带来的火灾风险。

分布式光纤压裂监测技术研究及应用

随着页岩油气等非常规油气勘探开发走向深层以及日趋精细化,微地震等传统压裂监测手段愈发无法满足压裂效果评价的精度要求。作为分布式光纤传感(DFOS)技术的最新研究进展,分布式光纤声波传感(DAS)近年来成为国内外压裂监测方向的研究热点。文中介绍了井下光缆布设、光缆深度标定、DAS信号处理、压裂期间DAS响应提取和解释的方法,并结合涪陵地区某页岩气井组的套管外光纤压裂监测实例,展示了DAS技术给非常规油气水力压裂监测带来的新视角和新认识,为我国压裂监测新技术的发展和推广应用提供参考。

基于光纤感测的急倾斜煤层采动围岩变形特征研究

将分布式光纤传感技术应用于急倾斜煤层采场围岩变形及应力分布特征物理相似模型试验,通过在模型中沿煤层倾向布置传感光纤与沿煤层底板铺设压力传感器,实时监测模型内部变形场与应力场,并结合数值模拟分析了急倾斜煤层顶板应变分布及演化特征。结果表明:工作面上部区域应力值小于下部和中部区域,中部区域应力值最大;随工作面推进,采空区底板应力逐渐释放,应力值不断降低,采空区两侧边界煤柱下方煤层底板应力逐渐升高,且中、下部采空区底板应力恢复程度显著高于上部底板;沿煤层倾向布置的光纤应变曲线呈三段分布,具有前后2处应变波峰区及采空区对应的中部波谷区,前波峰远高于后波峰;工作面中上部顶板变形程度大于下部顶板;数值模拟与光纤检测结果一致,均表现出中上部顶板变形显著大于下部。研究弥补了物理相似模型试验监测手段短板。

预应力混凝土梁腐蚀断丝水下监测试验研究

采用人工通电加速腐蚀的方法模拟混凝土梁内预应力钢筋的自然断裂过程从而获得真实的断丝声发射信号,应用高频声发射传感器和分布式光纤监测系统从水下采集预应力钢筋断裂时产生的声信号,分析信号的时频域特征和时域统计特征参数,结果表明:断丝信号的超声波段在水中传播时发生频散,应采用20 kHz以下的时域统计特征识别断丝信号;铠装光缆可以接收到在水中传播的断丝信号,其在时频图上表现为一条竖直的条带,并且能量主要集中分布于100~200 Hz。采用时域统计特征参数分析光纤监测信号时,需要设定较小的门槛值截取信号进行分析;对于光纤水声监测工况来说,峰值指标的信噪比较低,裕度和峭度指标更适合于用来识别断丝信号。该研究为开发预应力混凝土结构断丝水下声光纤监测系统奠定了基础。

基于分布式光纤的蜂窝夹层结构脱粘损伤监测

航空航天蜂窝夹层结构服役环境恶劣,需要发展相应的结构健康监测技术以保证结构的安全运行。脱粘损伤因发生在内部胶层而难以监测,该文采用埋入胶层的分布式光纤传感器对蜂窝夹层结构脱粘损伤进行监测。在预埋损伤监测试验中采用高强光纤和边界浅槽的方式提高传感器存活效率,得到脱粘损伤应变特征。采用参数化建模方式对不同损伤位置进行大量有限元模拟,加入白噪声后得到含有脱粘损伤特征的13500组数据。将模拟数据代入卷积神经网络进行训练,训练后的网络对试验损伤数据的识别准确率达到98.84%。该方法能够识别20 mm^(2)脱粘损伤,同时定位平均误差小于4 mm。

光纤传感技术在油气田开发中的应用

分布式光纤监测技术在油气田开发中具有无可比拟的优势。从分布式光纤传感技术基本原理和井中布设方式出发,介绍了光纤传感技术在水力压裂、连续油管产液剖面测试、邻井压裂监测、油气井注采监测、储气库安全监测和套损监测等多个石油工程领域应用情况。整体表明光纤监测是一种经济高效的监测技术,具备实时监控油气井全生命周期的潜力,是具有科学性、时代特性和安全高效的生产测井技术。同时指出分布式光纤传感技术在油田应用的未来发展应聚焦于提升传感器性能、丰富光纤监测场景应用、提高资料处理解释水平能力,降低应用成本,进一步发挥光纤在油气田开发中的作用。

光纤光栅传感器研发及其在土木工程中的应用进展

从传感器类型出发介绍了表贴式、纤维增强聚合物式、管式和内嵌式封装光纤布拉格光栅传感器的结构型式、实施方式和关键技术,简述了各种封装方式传感器的工作原理、技术研发及工程应用进展,总结了不同封装方式传感器的优势和不足。然后,简要介绍了光纤布拉格光栅传感器在桥梁结构状态监测或检测中的典型工程应用案例。最后,指出了光纤布拉格光栅传感器在土木工程领域中的工艺工法、耐久性和分布式测量以及未来推广应用有待解决的关键问题等,为光纤布拉格光栅传感器技术优化及其在土木工程中的推广应用提供参考。

分布式光纤传感技术在水力压裂中的研究进展

分布式光纤传感技术作为最新的水力压裂监测技术,应用于各大油田的水力压裂过程中,并且能够实现实时监测,已取得了显著的应用效果。为使业界进一步了解不同类型传感技术的基本原理、理论模型研究进展、现场应用情况,从分布式光纤温度传感技术和声波传感技术在水力压裂过程中的监测基本原理出发,系统总结了各类传感技术的理论模型研究进展和在产液剖面、裂缝扩展形态监测等方面的应用现状,最后提出了未来分布式光纤传感技术的发展方向。研究结果表明:①分布式光纤传感技术可以利用温度或者声波信号转换得到周围环境温度或应变的变化情况,从而实现水力压裂过程中的实时监测;②与分布式光纤声波传感技术相比,温度传感技术的相关理论模型相对较为成熟,能够实现产液剖面及裂缝形态的相关计算;③分布式光纤传感技术主要用于水力压裂过程中压裂液的注入、裂缝扩展等方面的监测。结论认为:分布式光纤传感技术可以有效地推动中国非常规储层的勘探和开发,同时提高水力压裂效果评价技术水平,这对中国油气行业的可持续发展具有重要推动作用。

桥梁缆索智能监测多参量光纤传感器及其封装保护技术

本文介绍了一种可直接植入缆索结构内部,实现缆索温度、湿度和应变多参量同步监测的新型光纤传感器。采用飞秒光纤光栅无损刻写技术制作缆索监测传感光纤,大幅提升了传感器耐久性。研发了基于聚酰亚胺套管的增敏型湿度传感器,大幅提升传感器测量灵敏度。提出了基于螺旋铠装+不锈钢套管的双层光纤传感器封装保护方案。研究了传感光纤从缆索锚头区域引出工艺,并开展了缆索试验研究,验证了本文研发的缆索监测多参量光纤传感器在实际缆索样品应用中的效果。