Computer Vision Techniques for Automatic Structural Assessment of Underground Pipes

Pipeline surface defects such as cracks cause major problems for asset managers, particularly when the pipe is buried under the ground. The manual inspection of surface defects in the underground pipes has a number of drawbacks, including subjectivity, varying standards, and high costs. An automatic inspection system using image processing and artificial intelligence techniques can overcome many of these disadvantages and offer asset managers an opportunity to significantly improve quality and reduce costs. This article presents a system for the application of computer vision techniques to the automatic assessment of the structural condition of underground pipes. The algorithm consists of image preprocessing, a sequence of morphological operations to accurately extract pipe joints and laterals (where smaller pipe is connected to main bigger pipe), and statistical filters for detection of surface cracks in the pipeline network. The proposed approach can be completely automated and has been tested on over 1,000 scanned images of underground pipes from major cities in North America.     

Segmentation of Pipe Images for Crack Detection in Buried Sewers

Abstract:   Assessing the condition of underground pipelines such as water lines, sewer pipes, and telecommunication conduits in an automated and reliable manner is vital to the safety and maintenance of buried public infrastructure. To fully automate condition assessment, it is necessary to develop robust data analysis and interpretation systems for defects in buried pipes. This article presents the development of an automated data analysis system for detecting defects in sanitary sewer pipelines. We propose a three-step method to identify and extract cracks from contrast enhanced pipe images. This method is based on mathematical morphology and curvature evaluation that detects crack-like patterns in a noisy pipe camera scanned image. As cracks are the most common defects in pipes and are indicative of the residual structural strength of the pipe, they are the focus of this study. This article discusses its implementation on 225 pipe images taken from different cities in North America and shows that the system performs very well under a variety of pipe conditions.     

探地雷达探测地下管道图像的定性研究

通过对生产实践中积累的不同管道材料、不同形状及不同充填条件下地下管道探地雷达图像的分析研究,总结了上述情形地下管道的探地雷达图像特征,总结对探地雷达地下管线探测资料进行定性解释的基本规律,以期对地下管道的性质及运行状况给出参考意见。     

顶管施工中相邻垂直交叉地下管线变形的三维有限元分析

顶管施工引起的管道周围土体移动会对相邻地下管线造成危害。采用三维有限元分析了顶管施工引起的相邻垂直交叉地下管线变形，研究了离顶管距离的远近、注浆、纠偏、不同管材、地下管线埋深、管线与土体弹性模量比等因素对地下管线位移的影响。研究表明：地下管线产生的竖向位移远大于水平位移，当顶管开挖面通过地下管线2m时，地下管线产生的竖向位移达到最大；顶管向地下管线侧纠偏是引起地下管线变形的主要原因；地下管线弹性模量越小，产生的位移越大。地下管线周围土体的弹性模量大小对位移有很大影响，可以通过注浆等方法加固土体以减小地下管线的位移。     

顶管施工引起邻近地下管线附加荷载的分析

利用弹性力学的Mindlin解,推导得到顶管掘进机与土体之间的摩擦力和后续管道与土体之间的摩擦力引起的土体附加应力计算公式。假定土体为Winkler模型,推导得到土体损失引起的垂直向土体附加应力计算公式。研究了顶管施工在邻近垂直交叉地下管线上引起的附加荷载分布规律。研究结果表明：附加荷载的变化规律与地下管线和掘进机的相对位置密切相关,是一个三维问题;随着地下管线与顶管之间距离的减小,附加荷载急剧增大;在正常施工时,竖直方向引起的附加荷载值最大,顶进方向其次,垂直于管壁方向最小。     

埋地热力管线腐蚀失效的形式

热力管线是城市基础设施的重要组成部分。热力管网输送高温高压水及蒸汽,均为危险介质,热力管线的突发破坏往往造成巨大经济损失,并引发安全事故。近年来由于城市建设、环境保护和节约能源的需要,管道直埋技术已然成为热力管网敷设的主流,但是随着埋入地下管道运行时间的推移,管道腐蚀失效问题日益严重,其安全问题的分析、评估和控制已经非常紧迫。本文综述了城市埋地热力管线的腐蚀失效形式,并针对当前城市特点及环境因素,对埋地热力管道的腐蚀失效形式进行了汇总和分类、分析。     

渗流条件下地埋管换热器传热特性研究

基于有渗流工况下地埋管管群的有限长线热源模型,通过Matlab软件模拟计算了深度为50 m平面处的地下温度场,根据地下温度场的温度分布,分析了布管方式,运行年限,孔隙率对地埋管管群传热效果的影响。研究表明:在物性参数,地埋管布管区域及地埋管总数不变的情况下,将地埋管等间距布置在布管区域内最有利于地源热泵系统的运行。地埋管布管区域冷热量累积效应在初始阶段较为明显,随着运行年限的增加,冷热量累积将在某一时刻达到动态平衡,此后将不随时间的增加而继续累积。对于冬夏季冷热负荷不平衡地区,孔隙率越大的区域越有利于地源热泵系统的运行。     

地下给水排水管道的结构检测

城市地下给排水管道工程所特有的工程隐蔽性、荷载条件的不明确性、埋设环境的影响使地下给排水管道工程的结构安全检测工作与普通钢筋混凝土结构检测工作相比,要复杂得多、困难得多;直接套用普通结构物的检测方法对地下管道进行结构检测,不但无法获得足够的检测数据,而且极有可能漏掉关系到地下管道安全的最重要的因素,得出错误的结果。北京市市政工程研究院充分考虑了地下给排水管道自身技术状态、管道承受的内外荷载、地下管道的埋设环境、邻近区域施工等多种影响因素,根据地下给排水管道结构检测的实际情况,提出了适用于城市地下给排水管道工程的“两环节、五阶段”检测方法,推动了地下给排水管道的结构检测工作。     

Automated detection of cracks in buried concrete pipe images

The detection of cracks in concrete infrastructure is a problem of great interest. In particular, the detection of cracks in buried pipes is a crucial step in assessing the degree of pipe deterioration for municipal and utility operators. The key challenge is that whereas joints and laterals have a predictable appearance, the randomness and irregularity of cracks make them difficult to model. Our previous work has led to a segmented pipe image (with holes, joints, and laterals eliminated) obtained by a morphological approach. This paper presents the development of a statistical filter for the detection of cracks in the pipes. We propose a two-step approach. The first step is local and is used to extract crack features from the buried pipe images; we present two such detectors as well as a method for fusing them. The second step is global and defines the cracks among the segment candidates by processes of cleaning and linking. The influences of the parameters on crack detection are studied and results are presented for various pipe images.     

富水地层盾构下穿施工引起的管线变形分析

隧道开挖导致的地层的沉降变形会通过外荷载的形式作用于邻近地下管线,使其受力性状发生变化,管线弯曲变形达到一定程度时,刚性管线可能出现裂缝甚至发生断裂。针对这一工程问题,文中以杭州地铁8号线浙江工商大学站-桥头堡站为工程背景,通过控制变量法,分析了盾构下穿埋深为1~6m的Q235钢管、铸铁管、C30混凝土管以及PVC管等多种工况下的管线引起的管线沉降变形规律,并根据分析结果对现有的通过地表沉降曲线最大斜率直接估算管线沉降变形情况及其安全性这一方法对各类管线的适用性进行了评价。然后,通过统计分析,提出了上述四种不同材质管线的管线最大沉降斜率与地表最大沉降斜率比值r随埋深h变化的线性拟合关系式,可以为通过观测地表最大沉降斜率估算地下管线最大沉降斜率提供参考。     

Automated detection of surface defects in water and sewer pipes

Automation is gaining momentum in industry, particularly in rehabilitation and inspection works of underground infrastructure facilities. This paper describes a model for automating inspection and identification of surface defects in underground water and sewer pipes. The paper describes the current efforts in identification of surface defects in underground water and sewer mains, and presents an automated system designed to assist infrastructure engineers in diagnosing defects in this class of pipe networks. It describes the general architecture of the system and its basic components, and focuses primarily on four modules designed for automating image acquisition, image processing, features extraction and classification of defects.     

地源热泵竖直地埋管系统设计的简明算法模型研究

根据对流换热、导热理论和能量平衡方程,在借鉴IGSHPA模型方法的基础上,得出了地埋管换热系统设计的简明算法模型。模拟值与实测值的比较结果表明,误差在工程允许范围之内。根据该算法能够得出相同换热量的不同埋管设计方案,即不同的埋深、管间距、管内流速和埋管数量的组合情况,同时也能得出相应的流体进出口温度。     

Water hammer in pressurized polyethylene pipes: conceptual model and experimental analysis

This paper analyzes the dynamic effects of pipe wall viscoelasticity on hydraulic transients. These effects have been observed in transient data collected from two polyethylene (PE) pipe systems. The first is a 270 m pipeline, 50 mm diameter, at Imperial College London, and the second is the world's longest experimental PE pipeline, 1.3 km long, 110 mm diameter, buried underground at Thames Water Utilities (London, UK). A mathematical model has been developed to calculate hydraulic transients in polyethylene pipe systems based on the assumption that the viscoelastic behaviour of pipe walls is linear. An additional term has been added to the continuity equation to describe the retarded deformation of the pipe wall and the resulting governing equations are solved by the Method of Characteristics. The numerical results are compared with both the classic elastic solution and with collected transient data. Good agreement between numerical results for the viscoelastic solution and observed data was obtained by fitting the creep function J(t). Unlike classic water hammer analysis, the developed mathematical model is capable of accurately predicting transient pressures in polyethylene pipes and the circumferential strains in the pipe walls.     

地源热泵系统地下埋管换热器设计(2)

讨论了地下埋管系统环路方式、埋管材料、埋管间距、埋管内工作流体的确定以及地下岩土热平衡的维持等问题。     

沉桩挤土效应对临近地下管线影响的试验研究

基于3×3群桩,采用PVC管模拟地下管线,完成了沉桩挤土效应对临近地下管线影响的模型试验,研究了沉桩过程中地下管线的应变变化规律,探讨了管线直径、埋深和与沉桩区域距离对地下管线应变的影响规律。结果表明,沉桩过程中,由于挤土效应,地下管线的应变逐渐增大,距沉桩区域很近时,管线有应变软化现象,且距离变化时,管线应变变化规律不尽相同;管线直径越大,抗弯刚度越大,应变越小;管线埋深越大,应变越大,但距沉桩区域较远时,出现管线埋深增加应变减小的现象;地下管线距沉桩区域越近,应变越大。试验结果对临近地下管线场地上沉桩施工具有重要的指导意义和实用价值。     

室内采暖系统埋地塑料管材的选型及安装要点

现阶段国内北方地区普通住宅项目户内采暖多采用埋地塑料管材,但针对埋地采暖管还没有完整的国家规范。地方标准也不能规范所有环节,容易出现选材不当、安装失误等影响用户使用的问题,不仅仅是室内热舒适度有所下降,甚至会造成不必要的经济损失。本文以某住宅项目为例,对埋地塑料管从选材、安装、运行等方面进行探讨,并对项目运行期间所出现的个别散热器不热等问题进行了深入分析。为今后相关工程的应用提供参考。     

交流电流衰减法（PCM）在埋地钢质管道防腐检测中的应斥

随着城市的建设和发展,埋地管线的种类和数量迅速增多,相应地也出现了涉及地下管线安全运行的各种腐蚀问题。因此开展埋地管道防腐层的非开挖检测非常必要。本文简要介绍了埋地管道非开挖检测常用的方法,然后具体围绕交流电流衰减法（PCM）的工作原理、检测前的准备展开讨论,并且以北京某地区的天然气埋地管道非开挖检测工作为例,介绍一则应用交流电流衰减法（PCM）进行埋地管道防腐层检测的工程实例,根据检测数据和管中电流随测量距离的变化曲线进行分析,确定了破损点的位置,并进行了开挖验证,将评价结果和开挖检测结果做了比较。之后指出了应用该法的局限性并提出相关建议。最后对未来的检测方法进行了展望。     

大同路雨污水顶管工程施工技术的应用

结合太原市大同路改造工程排水施工中顶管技术的应用,总结了顶管施工的工艺流程和技术要点,并进行了管道闭水试验,最后指出顶管技术对于地下水位较丰富及埋深较深的管道是较为优选的施工技术。     

埋地管线在爆炸地冲击作用下的数值模拟

常规武器钻地或地面爆炸地冲击作用下引起埋地管线上动应力如何计算及其是否安全,是一个值得研究的问题.利用LS-DYNA3D有限元程序,运用非线性动力学基本理论和算法,适当选取材料本构关系,对TNT药柱钻地和地面爆炸地冲击作用下引起埋地管线上动力响应问题,进行了数值模拟分析,得出了正对爆心的埋地管段背面部分易遭到材料受拉破坏,且受力过程是瞬态受力过程的结论.模拟计算结果与实验结果较为吻合,表明文中采用的数值模拟方法研究爆炸地冲击对埋地管线的作用是可行的.     

填土强度对埋地钢塑复合缠绕管受力影响分析

钢塑复合缠绕管是一种用于市政工程埋地排污排水的新型管道,在诸多性能方面优于传统的混凝土排水管,目前正在我国的城市建设中进行推广应用。这种管道外层为缠绕钢带,内层为高密度聚乙烯塑胶,是一种新型结构,在埋地受力机理方面,目前的研究做得尚不多。本文采用有限元的数值分析方法,针对不同的回填土情况,对这种管道的管土共同作用受力进行了分析,得出了填土强度对钢塑复合缠绕管管土共同作用受力的影响规律,可供相关的工程设计和施工参考。