Terrestrial laser scanning as a key element in the integrated monitoring of tidal influences on a twin-tube concrete tunnel

In 2012, for the first time in Belgium, integrated monitoring was carried out to assess the deformations of a twin-tube tunnel below the River Scheldt in Antwerp under the influence of estuarine tides. Levelling measurements during a tide cycle showed a variation in the height of levelling bolts of up to 10mm between low and high tide. Simultaneous strain-gauge measurements also showed a significant difference in strains. A deformation of the tunnel section during each twice-daily tide cycle, resulting in an eccentric egg or pumpkin shape, could hold large risks for the strength and durability of the tunnel structure. However, laser scanning results showed that there were no significant deformations of the tunnel's shape during the tide cycle. The laser scanning measurements resulted in a more thorough view of the deformation pattern which was much needed and improved the long-term risk assessment of the tunnel

Monitoring deformation of small scale model tunnels under load testing

This paper describes a study to assess the suitability of two non-contact methods of measurement used to monitor a series of small scale model tunnels built to different specifications that are being subjected to load testing. The model tunnels are being built to validate mathematical modelling techniques. Presented here are the results to assess the suitability and quality of survey results based on photogrammetry and laser scanning. The two key parameters to be measured are the deformation that is created in the tunnel (distance measurement) and the length and width of cracks. Results showed that both the remote measurement techniques were suitable for the measurement of the small model tunnels and compared well against appropriate potentiometer and vernier calliper measurements

Sensors for deformation monitoring of large civil infrastructures

In the maintenance of large infrastructures such as dams, bridges, railways, underground structures (tunnels, mines) and others, monitoring of deformations plays a key role in maintaining the safety serviceability conditions and for mitigating any consequences due to ageing factors and possible structural failures. [...]

The use of geomatic techniques to improve the management of metro infrastructure

The management of large infrastructures requires comprehensive knowledge of their characteristics and the elements that constitute them. It is essential to know which elements are involved and where they are located. At the same time also, it is vital to understand the overall geometry. However, it is difficult to obtain this information about underground infrastructures due to their lighting characteristics, hazards, lack of GNSS (Global Navigation Satellite System) signals and time available. In this case, to achieve the required quality in both tasks, the mobile mapping systems that are widely used in large surveys and urban inventories have to be adapted to obtain data in underground conditions. To achieve this, geodesic support is necessary. Therefore, a laser scanning and kinematic photogrammetry survey was carried out to obtain the centimetric precision and complete information that is still used today. This paper presents an adaptation of these systems for use in the Ferrocarril Metropolità de Barcelona.Peer ReviewedPostprint (author's final draft

Comparison study of precise monitoring techniques applied to engineering specimens tested under dynamic loading

Initially, the thesis shows a state of the art for structural health monitoring techniques and procedures. Different types of instrumentations and sensors employed under different requirements, which are presented with the view to monitor a variety of structural issues resulted by numerous conditions. It also presents examples from the literature following the proposed monitoring strategy as a novel pattern. These show how close-range digital photogrammetry and strain gauges have been employed in the past with the view to obtain strain evaluation assessments of the relevant monitored structural elements. Based on three surveys which have been carried out in a historical masonry church in Athens (Greece), the methodology of the thesis is generated with the experimental framework being also formed. Eight experiments have been carried out, five of them at the Advanced Structures Laboratory (CEGE – UCL), one at the Concrete Laboratory (CEGE – UCL) and two of them at the Earthquake and Large Structures Laboratory (EQUALS – University of Bristol). Two scale engineering specimens are employed for the experimental needs, both are scaled down using as a prototype element, the north-eastern wall of the studied church. The five experiments which are carried out in CEGE, are made on small scale masonry specimens, of 1/17th scale and the two experiments in EQUALS are made on large scale masonry specimens, of 1/5th scale. All the seven experiments are dynamically loaded. The only static loaded experiment is carried out at the Concrete Laboratory and it is made on a masonry specimen. Through the comparison of the two monitoring methods, close-range digital photogrammetry (CRDP) and strain gauges (SG), is concluded that both methods can capture a change in strain, on the tested specimens, when a crack is occurring

TOWARDS DESCRIBING FULL-SECTION DEFORMATIONS USING TERRESTRIAL LASER SCANNING IN THE BADALING TUNNEL (CHINA)

Abstract. This paper focuses on the analysis of point clouds from terrestrial laser scanning to interpret possible deformations of the new Badaling Tunnel that was built for the Winter Olympics 2022 in the nearby of Beijing, China. A reference framework is established to compare data corresponding to various days with blocks of uniform columns and rows from an estimated tunnel axis. Filling holes and detecting outliers are performed for quasi-planar estimation, and refinement transformation is used to adjust the data errors between different days. Finally, the full-section deformations are detected in the form of distance discrepancies of representative points and are verified against total station measurements

A review of the use of terrestrial laser scanning application for change detection and deformation monitoring of structures

Change detection and deformation monitoring is an active area of research within the field of engineering surveying as well as overlapping areas such as structural and civil engineering. The application of Terrestrial Laser Scanning (TLS) techniques for change detection and deformation monitoring of concrete structures has increased over the years as illustrated in the past studies. This paper presents a review of literature on TLS application in the monitoring of structures and discusses registration and georeferencing of TLS point cloud data as a critical issue in the process chain of accurate deformation analysis. Past TLS research work has shown some trends in addressing issues such as accurate registration and georeferencing of the scans and the need of a stable reference frame, TLS error modelling and reduction, point cloud processing techniques for deformation analysis, scanner calibration issues and assessing the potential of TLS in detecting sub-centimetre and millimetre deformations. However, several issues are still open to investigation as far as TLS is concerned in change detection and deformation monitoring studies such as rigorous and efficient workflow methodology of point cloud processing for change detection and deformation analysis, incorporation of measurement geometry in deformation measurements of high-rise structures, design of data acquisition and quality assessment for precise measurements and modelling the environmental effects on the performance of laser scanning. Even though some studies have attempted to address these issues, some gaps exist as information is still limited. Some methods reviewed in the case studies have been applied in landslide monitoring and they seem promising to be applied in engineering surveying to monitor structures. Hence the proposal of a three-stage process model for deformation analysis is presented. Furthermore, with technological advancements new TLS instruments with better accuracy are being developed necessitating more research for precise measurements in the monitoring of structures

An integrated multiscale approach for characterization of rock masses subjected to tunnel excavation

The design of tunnels must be conducted based on the knowledge of the territory. The longer the structure, the larger the area to be investigated, and the greater the number of surveys and tests to be performed in order to thoroughly examine all the relevant features. Therefore, optimization of the investigation process is strongly required to obtain complete and reliable data for the design of the infrastructure. The fast development of remote sensing technologies and the affordability of their products have contributed to proving their benefits as supports for investigation, encouraging the spreading of automatic or semi-automatic methods for regional scale surveys. Similarly, considering the scale of the rock outcrop, photogrammetric and laser scanner techniques are well-established techniques for representing geometrical features of rock masses, and the benefits of non-contact surveys in terms of safety and time consumption are acknowledged. Unfortunately, in most cases, data obtained at different scales of investigations are only partially integrated or compared, probably due to the missing exchange of knowledge among experts of different fields (e.g. geologists and geotechnical engineers). The authors, after experiencing such a lack of connection among the results of different surveys concerning tunnels, propose a multiscale approach for the optimization of the investigation process, starting from the regional scale, to obtain the data that can be useful not only for planning more detailed surveys in a preliminary phase, but also for making previsions on the discontinuity sets that are present in the rock masses subjected to excavations. A methodological process is proposed and illustrated by means of a case study. Preliminary results are discussed to highlight the potentiality of this method and its limitations. Keywords: Tunnel, Multiscale approach, Geological lineament, Non-contact survey, Discontinuity, Digital terrain model (DTM

Towards Long-Term Monitoring of the Structural Health of Deep Rock Tunnels with Remote Sensing Techniques

Due to the substantial need to continuously ensure safe excavations and sustainable operation of deep engineering structures, structural health monitoring based on remote sensing techniques has become a prominent research topic in this field. Indeed, throughout their lifetime, deep tunnels are usually exposed to many complex situations which inevitably affect their structural health. Therefore, appropriate and effective monitoring systems are required to provide real-time information that can be used as a true basis for efficient and timely decision-making. Since sensors are at the heart of any monitoring system, their selection and conception for deep rock tunnels necessitates special attention. This work identifies and describes relevant structural health problems of deep rock tunnels and the applicability of sensors employed in monitoring systems, based on in-depth searches performed on pertinent research. The outcomes and challenges of monitoring are discussed as well. Results show that over time, deep rock tunnels suffer several typical structural diseases namely degradation of the excavation damaged areas, corrosion of rock bolts and cable bolts, cracks, fractures and strains in secondary lining, groundwater leaks in secondary lining, convergence deformation and damage provoked by the triggering of fires. Various types of remote sensors are deployed to monitor such diseases. For deep rock tunnels, it is suggested to adopt comprehensive monitoring systems with adaptive and robust sensors for their reliable and long-lasting performance