Automatic multi-image stitching for concrete bridge inspection by combining point and line features

Most of the current techniques for concrete bridge inspection are based on human visual interpretation, which often is dangerous and time-consuming. To address this problem, we introduce in this paper a newly developed vehicle-based robot inspection system that can automatically capture thousands of bottom surface images with a group of high-resolution industrial cameras, which are then stitched into a single composite image. However, traditional image stitching methods generally fail with large drift due to the great number (more than 2000) and sparse texture of linearly distributed images in sequence. Therefore, a novel image stitching method was developed for our robot inspection system, which combines both the 2D image point features and the 3D line features to reduce the drift. First, the bottom surface images are arranged into different strips based on their acquisition order and rough poses, and images in a single strip are divided into several groups. Then, the proposed image stitching method is performed in a bottom-up way, as follows: 1) the images within a single group initially are aligned via their point and line features; 2) the groups within a single strip are then stitched together via a homographic refinement procedure; 3) the strips are aligned into a single composite image that completely covers the bottom surface of the bridge; and 4) after all the stitching procedure are complete, a multi-band blending algorithm is applied to generate the mosaicked panorama as seamlessly as possible. The experimental results on a set of representative images acquired from the bottom surfaces of a real bridge demonstrate the capabilities and the limitations of the proposed approach.     

双层越江隧道联络通道冻结法温度场影响因素

上海复兴东路越江隧道为国内首条双层隧道,其联络通道采用水平冻结信息化施工.对施工全过程的监测结果表明,冻结管布置形式、管片散热是影响冻土帷幕形成的重要因素.通道段单排管布置、喇叭口双排管加强的布置方式使冻土帷幕形成三个性状不同的区域,隧道管片散热显著影响了喇叭口部位冻土帷幕的特征.通过冻土帷幕的厚度和平均温度描述了三个区域的性状,并通过定义隧道管片散热影响系数,分析了隧道管片散热对冻土帷幕厚度的影响程度以及影响范围.所得到的结论为将来施工类似工程提供有益借鉴.     

Assessment the influence of ground stratification,tunnel and surface buildings specifications on shield tunnel lining loads (by FEM)

Urban development and rapid extension of cities have been accompanied by a considerable growth in mechanized shield tunnelling. Commonly precast concrete segments are used as tunnel lining which comprises relatively considerable part of tunnelling cost. The optimum design of lining needs to an accurate evaluation of loads acting on the lining.In this paper, the effects of ground stratification, surface buildings specifications and tunnel depth on lining loads were studied. For this purpose a 3D finite element model was used employing the ABAQUS software (Ver. 6.11). The geometry of tunnel, lining segments, injection grout and the surrounding soil properties were adopted from the under construction Tabriz urban railway line 2 project.The results show that the studied parameters have considerable effects on lining loads. For mentioned case study, surface buildings with 5 and more story have a considerable effect on lining loads, especially for shallow tunnels. The geometry of surface buildings influences the internal forces of the tunnel lining and increase of buildings width and length increases the lining loads. The building width is the most important parameter and with increase of that the influence of other parameters increases. Also by comparison of obtained results in this study with results of 2D analysis, reliability of 2D models was investigated. The comparisons show that 3D analysis is superior to 2D analysis, particularly in the cases of surface buildings presence. The difference between results increases with decrease of building length and increase of tunnel depth and building weight.     

A new 3D observation system designed for a seismic ahead prospecting method in tunneling

The tunnel seismic ahead prospecting method is usually used to estimate adverse geology ahead of a tunnel face. The observation system plays an important role in tunnel seismic ahead prospecting, which helps to obtain accurate imaging results. Optimizing the observation system is a key issue for seismic ahead prospecting. In this paper, observation layouts are evaluated and a new three-dimensional (3D) observation system is proposed by imaging results analysis. For linear and 3D layouts, imaging result analysis in this paper indicates that the mirror artifact caused by the linear layout (Which sets sources and geophones on a straight line) can be suppressed by the 3D layout, due to its energy concentration and convergence. Moreover, reflections using 3D layout identify real abnormal bodies better than the linear layout. Moreover, conventional observation layouts often use shot point on the tunnel face or front sidewall, which makes it difficult to filter interference waves from the back of the tunnel face. To solve this problem, typical numerical examples are conducted, and imaging results of observation layouts with shot point on front sidewall, tunnel face or back sidewall are studied. Results show shot point on the back sidewall helps to separate waves, suppress interference waves and extract effective waves (reflected P-waves by discontinuities) by apparent velocity filtering method, so shot point is designed on the back sidewall to get high-quality records. To balance record quality and application convenience, a new 3D observation system is proposed with 12 geophones and 10 shot points in a special arrangement. Compared with a linear layout, practical testing and application using the new 3D system indicate the main fractured zones are accurately identified and located, which proves the reliability and practicability of the new observation system.     

3D Object Classification Using Geometric Features and Pairwise Relationships

Object classification is a key differentiator of building information modeling (BIM) from three‐dimensional (3D) computer‐aided design (CAD). Incorrect object classification impedes the full exploitation of BIM models. Models prepared using domain‐specific software cannot ensure correct object classification when transferred to other domains, and research on reconstruction of BIM models using spatial survey has not proved a full capability to classify objects. This research proposed an integrated approach to object classification that applied domain experts’ knowledge of shape features and pairwise relationships of 3D objects to effectively classify objects using a tailored matching algorithm. Among its contributions: the algorithms implemented for shape and spatial feature identification could process various complex 3D geometry; the method devised for compilation of the knowledge base considered both rigor and confidence of the inference; the algorithm for matching provides mathematical measurement of the object classification results. The integrated approach has been applied to classify 3D bridge objects in two models: a model prepared using incorrect object types and a model manually reconstructed using point cloud data. All these objects were successfully classified.     

Application and validation of simple image-mosaic technology for interpreting cracks on tunnel lining

As a simple, portable method that uses inexpensive tools for structural safety inspections of tunnels, this study presents a novel image-mosaic technology that generates layouts of tunnel wall surfaces. Geometric distortion in camera images of 3D tunnel surfaces is rectified through equations related to projection characteristics and the bilinear interpolation method. Successive taken images with at least four reference points in each one are then resampled to a 2D coordinate for the layout of tunnel surfaces. Test results for a laboratory-scale tunnel demonstrate that the spatial accuracy of the proposed image-mosaic technology for a mosaicked layout from vertical images is approximately 1.6° with sufficient image resolution for detecting lining cracks with widths exceeding 0.45 mm. Field application to a full-size, operational tunnel indicates that the layout of tunnel wall surfaces by the proposed technology is sufficient for identifying lining crack distributions and detecting temporal variations in cracks.     

Shaking table tests on seismic measures of a model mountain tunnel

A series of three dimensional (3D) shaking table tests were carried out to investigate the mechanism and effect of seismic measures of mountain tunnel using a scaled model based on a real tunnel. Key technical details of the experiment, including similarity relations, seismic measures simulation, boundary conditions, sensor layout, modeling methods, and ground motion input were presented. Main seismic measures, including reinforcing surrounding rock with anchors, increasing lining flexibility with steel wire mesh, and installing seismic isolation layer between reinforced surrounding rock and tunnel lining, were investigated in this study. Experiment results show that: (1) adding a layer of steel wire mesh in the tunnel lining can improve the flexibility and seismic performance and also may effectively prevent radial cracks from crossing the lining; (2) installing a geofoam isolation layer between the reinforced surrounding rock and the tunnel lining reduces dynamic earth pressure by 70–90% for the lining without a seismic isolation layer; (3) the flexible joints can effectively avoid global failures of tunnel lining for they reduce dynamic strain and bending force in the tunnel lining and decrease the seismic energy transmission along the lining in axial direction; (4) reinforcing surrounding rock with anchors significantly reduces dynamic earth pressure and strain of the lining by about 50%. In addition, the length of seismic reinforcement for general mountain tunnel portal is recommended to be 50 m from the tunnel portal along the axial direction.     

Interaction of tunnel linings and soft ground

Although soil-lining interaction is highly dependent on the tunnelling technology used, most of the available design methods for tunnel linings fail to take into consideration this important factor. During tunnel excavation, the in-situ stresses are significantly altered, depending on the tunnelling technique as well as the configuration of the tunnel and the characteristics of the soil deposits. The reduced radial stresses are the starting point of the soil-lining interaction at lining activation. This paper presents a method of lining design that considers the details of the excavation procedure and lining installation. Interaction between the tunnel lining and the ground is analysed in two stages—excavation and interaction. The excavation stage is responsible for determining the pre-lining soil deformations and the reduced in-situ stresses. The interaction stage models the soil-lining system together. Soil continuum, tunnel lining, and the interface between them are idealized in the whole system using nonlinear finite-element techniques. The deformations of the soil-lining system, as well as the lining internal forces, and equilibrium soil pressures are determined. Finally, results of the proposed analytical method as well as commonly used procedures are compared with field measurements compiled during the construction of two tunnels in which a precast segmental lining and rib and lagging lining were used.     

电力电缆隧道结构病害及检测评估方法探讨

电力电缆隧道是目前常见的城市地下空间利用形态之一,但是该类隧道的结构病害检测技术体系和规范尚不完善,影响了该类隧道的病害评定及相应处治。电力电缆隧道的病害类型主要包括隧道渗漏水、隧道衬砌裂损、衬砌结构腐蚀这三大类型,其中影响较大的为隧道渗漏水。在电力电缆隧道的检测工作中,需要结合电力隧道的工作环境条件、功能特点,明确检测的目的和需求,有针对性地调查和收集相关的信息和资料以制定检测方案。检测的内容可以划分为外观检查、结构安全性检查、结构耐久性检查这三大类内容,以便选取适宜的仪器和方法开展电力隧道检测工作。论文提出了确定电力隧道结构区段的分项评定标准及综合技术状况评定方法,并建议依据检测评定结果对电力隧道采取对应的养护措施。     

移动三维激光扫描技术在地铁隧道病害检测中的应用

常见的地铁隧道病害有渗漏水、裂缝、错台、侵界等,这些地铁隧道病害的存在会对隧道的安全使用造成不好的影响.因此,需要定期对隧道的病害进行检测,并进行相应的修复.对于地铁隧道病害检测,常用的方法有人工巡检方法、全站仪方法等,这些方法效率低下且采集信息量有限.针对这些问题,使用一种自主研发的移动三维激光扫描系统进行隧道检测....     

光滑接触条件下隧洞支护断面形状优化

 假定衬砌与围岩为光滑接触,在满足隧洞净空尺寸和衬砌厚度的前提下,以使衬砌内边界上的切向应力最小为优化准则,寻求最优的支护断面形状。寻优过程是解决一类几何反问题的过程,相应的正问题运用平面弹性复变函数中的保角变换方法进行求解。寻优时,衬砌内边界的切向应力即为优化的目标函数,映射函数系数为设计变量。运用混合罚函数优化方法寻找目标函数的极小值,可以获得能满足给定约束条件的最优支护断面形状。优化后的衬砌断面形状可以最大限度地改善隧洞衬砌的应力状态,保证衬砌内边界获得最小的应力集中。     

甘肃某高速公路隧道二衬裂缝成因及整治技术研究

依托甘肃某高速公路8座隧道维修工程,以专项检测数据、现场调查及维修期间揭露的情况为依据,结合各个隧道的原设计、施工、运营、检测评估情况,采用排除法对隧道二次衬砌裂缝的成因进行了深入分析,指出衬砌产生裂缝的主因是隧底仰拱缺陷,其引发衬砌不均匀沉降,致使衬砌局部混凝土受拉产生裂缝,而衬砌背后脱空和厚度不足减小了衬砌刚度,引发应力集中效应进一步恶化了衬砌受力状态。以衬砌裂缝病害的发育情况和隧道质量缺陷(衬砌厚度、仰拱厚度)二者间的相关性情况为出发点,提出了针对衬砌裂缝产生原因的处治方案,取得了良好的维修效果。     

海底隧道衬砌结构设计

 海底隧道围岩水通常具有稳定水位和充足补给,隧道结构受长期的水压力作用,衬砌计算中应首先确定水压力荷载大小,并综合考虑隧道涌水量的大小,由此对衬砌断面的拟定、衬砌类型的选择、衬砌结构安全性进行评价计算。正在建设的厦门翔安海底隧道衬砌结构设计时,通过不同防排水方式下衬砌背后水压力特征的模型试验表明,作用于全封闭衬砌上的水压力是不能折减的;根据陆域和海域不同地段预测全隧道涌水量,由于无法满足运营期间的排水,衬砌结构必须采用全封闭形式或限制排放形式;利用ANSYS有限元软件,根据外水压力大小与围岩压力组合下对不同的隧道衬砌断面进行对比分析计算,以得出结构受力最为经济合理的断面形式;并以此断面按荷载结构模式法进行全封闭衬砌结构计算。计算结果及建设的实际情况表明衬砌受力合理。     

BIM技术在隧道衬砌病害信息可视化中的应用

对BIM技术在运营公路隧道衬砌结构病害检测结果信息可视化展示中的应用展开了研究,通过对AutoCAD和Revit的二次开发,实现隧道衬砌病害的三维可视化。所实施的方法为:将公路隧道的结构进行解构,以便在BIM软件中建立隧道各个构件的空间模型;结合隧道结构特征,推导出将CAD平面图形元素映射到三维隧道空间结构的转换公式;提取隧道病害展示图中特征点的关键参数,把提取的隧道病害的参数进行坐标换算,将隧道病害元素映射到隧道结构的空间模型上,实现了衬砌病害从二维向三维的转化。通过BIM技术展示衬砌病害的三维可视化,为公路隧道的维修养护工作提供便利。     

Metrics and methods for evaluating model-driven reality capture plans

This paper presents new metrics and methods for evaluating the quality of reality capture plans—commonly used to operate camera-mounted unmanned aerial vehicles (UAVs) or ground rovers—for construction progress monitoring and inspection of as-is conditions. Using 4D building information model (BIM) or 3D reality model as a priori, these metrics provide feedback on the quality of a plan (within a few minutes), accounting for resolution, visibility, accuracy, completeness of the capture, and satisfying battery capacity and line-of-sight requirements. A cloud-based system is introduced to create and optimize UAV/rover missions in the context of prior model. Results from real-world construction data sets demonstrate that the proposed metrics offer actionable insights into the accuracy and completeness of reality capture plans. Additionally, a capture plan—with a combination of canonical and noncanonical camera views—that satisfies the introduced metrics is statistically correlated with the quality of reconstructed reality. These metrics can improve computer-vision progress monitoring and inspection methods that rely on the construction site's appearance and geometry.     

海底隧道衬砌结构选型及参数优化研究

海底隧道不同于陆上隧道,海水位变化相对隧道埋深较小,隧道两端出口比海底部分要高,不能采用自然排水。深埋海底隧道二次衬砌承受较大的外水压力。调查了国内外海底隧道衬砌结构型状及支护参数,针对海底隧道的特殊性,归纳了海底隧道设计理念和设计方法。针对某公路海底隧道特定地质条件和工程设计要求,分别采用马蹄形、椭圆形、圆形3种衬砌结构型式,并用有限元软件对这3种衬砌结构二次衬砌在不同荷载作用下进行强度验算。对计算结果优化比选,选出一种技术可行、经济合理的衬砌结构,得出一些有意义的结论。     

矿山巷道三维建模及其空间距离近似计算

大型矿山通常有复杂的巷道系统,传统的平面设计难以清晰表达巷道之间的空间关系,使工程技术人员不能直接获取巷道系统的空间分布特征。本文尝试采用三维建模进行巷道的空间优化布置,将其分解为断面设计和轴线设计,采用拖拉的方法生成巷道的三维实体模型。借助地理信息系统中的空间分析方法,建立巷道模型与轴线、断面之间的连接关系,借助该连接关系,提出一种三维巷道的空间最短距离的近似计算方法,即先计算轴线之间的空间最短距离,然后再减去两端截取部分,可得到空间任意巷道之间近最短近似距离。最后,将该方法应用于安徽某煤矿工程。     

不同倾角逆断层错动对隧道结构影响理论分析

结合某隧道工程项目,采用FLAC3D有限差分软件,建立相应的数值模型,分析由于地震引发的逆断层错动作用对正交穿越断层隧道的影响,并揭示其影响机理。结果表明断层错动对主动盘内隧道的影响范围远大于被动盘,断层两侧隧道衬砌竖向相对位移随着错距量的增加而发生线性增长,且断层对衬砌影响范围不受错距大小的影响。在断层上盘与下盘之间挤压力的作用下,衬砌边墙处最容易发生拉裂破坏和剪切破坏,为最不利位置,拱顶次之,仰拱所受影响最小。在逆断层倾角一定的情况下,随着错动距离的增大,衬砌不同部位受到的最大主应力、最小主应力、剪应力均整体呈增大趋势。对依托工程隧道的安全性和可靠性进行评价,同时对类似特殊修建条件下隧道的设计和施工具有一定的指导作用。     

滑坡区隧道自锚式新型加固结构理论研究

 针对位于深厚滑坡体中隧道的加固问题,提出了利用锚索、抗滑桩只对与隧道稳定直接相关的洞周滑坡体进行抗滑及锚固处治,同时加固隧道衬砌结构,使隧道衬砌结构、抗滑桩与锚索形成一种新型的滑坡隧道自锚式加固结构体系。该加固结构将滑床作为桩和锚索稳定的支撑点,属于超静定结构。针对该加固结构体系的特点建立其物理力学模型,并采用矩阵传递法进行理论推导,得到加固结构体系的内力与位移。通过算例分析结果表明,锚索的作用使隧道边墙不利受力状态有所改善,抗滑桩对隧道底铺和衬砌的变形有所约束,可以通过锚索和抗滑桩结构,使隧道衬砌结构的受力和变形得到优化控制。     

隧道受震破壞調查分析與修復管理案例

就隧道震後之災損模式進行統計與災損原因研判,並利用數值分析方法研判安全性,就結構加固等改善措施之設計考量作詳細說明;另由於隧道結構物的損壞範圍大,且修復經費受限,必須藉由定期檢测進行長期維護管理,以防範意外發生。於此,利用Vidco-GIS自動化影像地理资訊系統之e化新技術,以動態及靜態影像紀錄隧道災損狀況,同時亦整合建置前期設計、施工圖及定期維護等資料,相關成果以資料庫方式纳入日常維護管理,以有限人力有效率地進行維護管理紀錄並随時掌握現況供作決策之明確參考。