Использование оптического волокна G-652 для контроля горного массива угольных шахт

Introduction. The relevance of using fiber-optic sensors to monitor the geomechanical state of the mine workings of coal mines of the Karaganda coal-mining field is extremely high, because they are super-categorical and dangerous in a sudden explosion of coal dust and methane gas during mining operations in hazardous mines. Fiber optic sensors have several advantages: explosion safety, high accuracy, measurement speed and have good linearity of characteristics. Aim. The use of optical fiber of the ITU-T G.652.D standard as a sensor for monitoring the geomechanical state of an array of coal mines, which is very promising in terms of creating a distributed monitoring system capable of timely signaling to personnel about the danger of a sudden collapse of a mine. Materials and methods. To develop methods for monitoring and measuring the geotechnical parameters of the workings, a simulation laboratory bench based on fiber-optic sensors was developed. The authors used a quartz single-mode optical fiber 9/125 μm (OS2) Corning SMF-28e + ®. The article proposes systems in two variants, depending on the tasks and functionality. In the first variant, the well-known method of optical reflectometry OTDR (Optical time domain reflectometer) is used. In the second variant, the values of the additional losses caused by the mechanical action on the optical fiber are controlled. Results. During mechanical action on an optical fiber microcracks occur, leading to a change in the properties of light and an increase in additional losses of the light wave passing through it. Conclusion. The use of ITU-T G.652.D standard optical fiber for monitoring the geomechanical state of an array of coal mine workings is very promising, since the VODs developed on its basis have sufficiently high accuracy, measurement speed and good linearity of characteristics.Введение. Актуальность использования волоконно-оптических датчиков для контроля геомеханического состояния массива горных выработок угольных шахт Карагандинского угольного бассейна крайне высока, потому как они относятся к сверхкатегоричным и опасным по внезапному взрыву угольной пыли и газа метана при проведении горных работ в опасных условиях шахт. Волоконно-оптические датчики обладают рядом достоинств: взрывобезопасностью, высокой точностью, скоростью измерения и имеют хорошую линейность характеристик. Цель исследования. Использование оптического волокна стандарта ITU-T G.652.D как датчика для контроля геомеханического состояния массива горных выработок угольных шахт, что является весьма перспективным в плане создания распределенной системы мониторинга, способной своевременно сигнализировать персонал об опасности внезапного обрушения выработки. Материалы и методы. Для отработки методов контроля и измерения геотехнических параметров выработок был разработан имитационный лабораторный стенд на основе волоконно-оптических датчиков. Авторами использовалось кварцевое одномодовое оптическое волокно 9/125 мкм (OS2) Corning SMF-28e+®. В статье предложены системы в двух вариантах исполнения в зависимости от поставленных задач и функциональности. В первом варианте используется известный метод оптической рефлектометрии OTDR (Optical time domain reflectometer). Во втором варианте контролируются значения дополнительных потерь, вызванные механическим воздействием на оптическое волокно. Результаты. При механическом воздействии на оптическое волокно возникают микротрещины, приводящие к изменению свойств света и увеличению дополнительных потерь световой волны, проходящей по нему. Указанные потери можно измерить и установить значения давления на оптическое волокно, также можно определить величину смещения. Заключение. Использование оптического волокна стандарта ITU-T G.652.D для контроля геомеханического состояния массива горных выработок угольных шахт является весьма перспективным, так как разработанные на его основе волоконно-оптические датчики обладают достаточно высокой точностью, скоростью измерения и имеют хорошую линейность характеристик

SHM with DOFS of the TMB L-9 tunnel affected by nearby building construction

Degut a la construcció d´un edifici proper, el túnel de la línia 9 es pot veure afectat en el seu estat de deformació i tensional. Per tal de fer un seguiment continuu durant tot el periode de treballs, es planteja una monitorització de la volta i llossa del túnel amb un sensor de fibra òptica distribuïda, que permetrà obtenir les deformacions al formigó amb una resolució de l´ordre de 1 centímetr

Fiscal Year 2002

The Department of Energy (DOE) and its predecessors have conducted research and development (R&D) in geothermal energy since 1971. To develop the technology needed to harness the Nation's vast geothermal resources, DOE's Office of Geothermal Technologies oversees a network of national laboratories, industrial contractors, universities, and their subcontractors. The goals are: (1) Double the number of States with geothermal electric power facilities to eight by 2006; (2) Reduce the levelized cost of generating geothermal power to 3-5 cents per kWh by 2007; and (3) Supply the electrical power or heat energy needs of 7 million homes and businesses in the United States by 2010. This Federal Geothermal Program Research Update reviews the specific objectives, status, and accomplishments of DOE's Geothermal Program for Federal Fiscal Year (FY) 2002. The information contained in this Research Update illustrates how the mission and goals of the Office of Geothermal Technologies are reflected in each R&D activity. The Geothermal Program, from its guiding principles to the most detailed research activities, is focused on expanding the use of geothermal energy. balanced strategy for the Geothermal Program

Nondestructive Testing (NDT)

The aim of this book is to collect the newest contributions by eminent authors in the field of NDT-SHM, both at the material and structure scale. It therefore provides novel insight at experimental and numerical levels on the application of NDT to a wide variety of materials (concrete, steel, masonry, composites, etc.) in the field of Civil Engineering and Architecture

Fiscal Year 2003

The Department of Energy (DOE) and its predecessors have conducted research and development (R&D) in geothermal energy since 1971. To develop the technology needed to harness the Nation's vast geothermal resources, DOE's Office of Geothermal Technologies oversees a network of national laboratories, industrial contractors, universities, and their subcontractors. The following mission and goal statements guide the overall activities of the Office. The goals are: (1) Reduce the levelized cost of generating geothermal power to 3-5 cents per kWh by 2007; (2) Double the number of States with geothermal electric power facilities to eight by 2006; and (3) Supply the electrical power or heat energy needs of 7 million homes and businesses in the United States by 2010. This Federal Geothermal Program Research Update reviews the accomplishments of DOE's Geothermal Program for Federal Fiscal Year (FY) 2003. The information contained in this Research Update illustrates how the mission and goals of the Office of Geothermal Technologies are reflected in each R&D activity. The Geothermal Program, from its guiding principles to the most detailed research activities, is focused on expanding the use of geothermal energy. balanced strategy for the Geothermal Program

Tunnel Engineering

This volume presents a selection of chapters covering a wide range of tunneling engineering topics. The scope was to present reviews of established methods and new approaches in construction practice and in digital technology tools like building information modeling. The book is divided in four sections dealing with geological aspects of tunneling, analysis and design, new challenges in tunnel construction, and tunneling in the digital era. Topics from site investigation and rock mass failure mechanisms, analysis and design approaches, and innovations in tunnel construction through digital tools are covered in 10 chapters. The references provided will be useful for further reading

Experimental Evaluation of a Distributed Fiber Optic Sensor for Mining Application

Triggered remote seismic events have been widely studied in the earthquake engineering context where various possible explanations have been provided, including directivity of dynamic stresses, a critically stressed environment, the presence of hydrothermal geological environments at remote distances, and so on. Similar events have been observed in underground mining regions; however, they have rarely been studied in terms of the underlying mechanisms such as the presence of faults of marginal stability, increases in the stress gradient between mined out regions as a result of connective fractures, unclamping effect on geological features such as dikes or joint swarms, and so on. This research was triggered in part by the hypothesis that remote seismic events in mines could be triggered when gravity-driven displacements are transferred to distances far from active mining (10’s to 100’s of metres). Accordingly, the thesis focuses on experimental research on a novel deformation sensing sensor for future verification of this assumption. A secondary focus is mathematical modeling to help understand the deformation mechanisms and magnitudes that may take place in a jointed rock mass. Distributed Brillouin sensing systems (DBSs) have found growing applications in engineering and are attracting attention in the field of underground structures including mining. The capability for continuous measurements of strain over large distances makes DBSs a promising monitoring approach for understanding deformation field evolution within a rock mass, particularly when the sensor is installed away from “excavation damaged zones” (EDZ). A purpose-built fiber optic sensing cable, a vital component of DBSs, was assessed in laboratory conditions to establish the capability and limitations of this technology to monitor deformation fields over large distances. A test program was performed to observe DBSs response to various perturbations including axial and shear strain resulting from joint movements. These tests included assessments of the strain-free cable response and the application of extensional and lateral displacement to various sensing cable lengths (strained lengths from 1 m down to 1 cm). Furthermore, tests were done to evaluate the time-dependent behavior of the cable and to observe the effect of strain transfer using a soft host material (i.e., a soft grout) under lateral displacement. The noise level of the DBSs range was ±77 µε, determined through repeated measurements on an unstrained cable. Stretching test results showed a linear correlation between the applied strain and the Brillouin frequency shift change for all strained lengths above half the spatial resolution of the DBSs. However, for strained lengths shorter than half the spatial resolution, no strain response was measurable and this is due to the applied internal signal processing of the DBSs to detect peak Brillouin gain spectrum and noise level. The stability with time of the measurements was excellent for test periods up to 15 hours. Lateral displacement test results showed a less consistent response compared to extension tests for a given applied displacement. The Brillouin frequency shift change is linearly correlated with the applied displacement in tension but it shows a parabolic variation with lateral displacement. Moreover, the registered frequency response (correlated with strain) of the system decreased significantly when the sensing cable was embedded in a sand-filled tube compared with direct cable displacement. A comprehensive laboratory scale testing program was undertaken to study the response of the system to different loading paths in time and space domains. Purely extensional displacement fields were applied to demonstrate that the system could produce repeatable displacement responses for three different configurations of distributed strained patterns. A borehole installation method was developed by testing the sensing cable’s response while embedded in mortar beams. When the cable is directly embedded in the mortar, uncontrolled self-debonding happens that introduces uncertainties in the measurements. This limitation was overcome by anchoring debonded sections of the sensing cable at regular spacing. This arrangement produced consistent strain patterns for each strained interval. It was shown that the performance of the debonded sections changes for longer anchor spacing and for closely spaced joints where more than one joint crosses the debonded interval. The influence of borehole diameter and strength of the filling material were evaluated for their possible effects on the strain transfer process to the sensing cable. With the anchored arrangement of debonded cables, these properties of the grout did not have a measurable effect on the results, and as long as the tensile strength of the grout is low enough to break at the joint locations, the strain transfer performance from the rockmass to the sensing cable was excellent. A study was devoted to understanding such a deformation monitoring system under various shear displacement conditions. These included the difference in response of the system in direct shear compared to tests performed in direct tension. The system response was evaluated for various strained lengths as well as distances over which the bending strains are acting (kink lengths). The latter was found to be an important factor influencing monitoring results. In addition, the system behavior under shear displacement where the sensor is inclined with respect to the joint strike was evaluated to understand the effect of a combined extension and shear displacement. The effect of the existence of two joints over the strained lengths was assessed in both direct and inclined shear. A new relation was established between the registered Brillouin frequency shift change and all contributing components of deformation when the sensor is elongated while under shear displacement. The testing program shows that Distributed Brillouin Sensing (DBS) technology has promise for detecting deformations over long distances. Not only strain localization occurring at pre-existing discontinuities or at developing cracks can be detected by this sensor, but also strain levels well below the typical damage initiation threshold (~0.1%) for hard brittle rocks are above the basic noise level of the system. However, the sensing element is quite fragile when under shear displacement and can easily break at small shear displacements. Therefore, it is better to have an idea of the dominant deformation mechanism in the rock mass before the installation of the sensor. The sensor would be much more durable where the rock mass experiences less shearing. Mathematical simulations of a 2D rock mass were carried out using the distinct element method. Two major parameters including interlocking degree and pre-existing conditions such as mined-out zones at higher levels were studied. Different rock mass models with varying block sizes, joint set orientations, and joint persistency were built to study the effect of interlock on the displacement pattern away from mining. In general, displacement as large as 5 cm could travel distances as far as 500 m away from the active mining zone. The exact displacement pattern is largely controlled by the characteristics of the joints sets. However, the transfer of large displacements was limited to distances of the size of the mining boundary, where rock mass interlocking promote arching. Furthermore, with non-persistent joint sets, a few shear slip events were noticed at higher levels whereas more remote joints did not show slip. All slip events were close to the mining boundary. Remote shear slip events, could not be generated by changing parameters representing the degree of interlock in the rock mass. When a backfilled old mine was added to the middle height of the model, some 500 m away from active mining, results showed that a large number of joints around the old mining zone slipped due to displacements induced by the distant deeper mining. It was found that the pre-existing excavation and the mine extraction strategy is a critical factor for providing conditions under which such slip events at remote distances occur from active mining

Geotechnical Engineering for the Preservation of Monuments and Historic Sites III

The conservation of monuments and historic sites is one of the most challenging problems facing modern civilization. It involves, in inextricable patterns, factors belonging to different fields (cultural, humanistic, social, technical, economical, administrative) and the requirements of safety and use appear to be (or often are) in conflict with the respect of the integrity of the monuments. The complexity of the topic is such that a shared framework of reference is still lacking among art historians, architects, structural and geotechnical engineers. The complexity of the subject is such that a shared frame of reference is still lacking among art historians, architects, architectural and geotechnical engineers. And while there are exemplary cases of an integral approach to each building element with its static and architectural function, as a material witness to the culture and construction techniques of the original historical period, there are still examples of uncritical reliance on modern technology leading to the substitution from earlier structures to new ones, preserving only the iconic look of the original monument. Geotechnical Engineering for the Preservation of Monuments and Historic Sites III collects the contributions to the eponymous 3rd International ISSMGE TC301 Symposium (Naples, Italy, 22-24 June 2022). The papers cover a wide range of topics, which include: 　 - Principles of conservation, maintenance strategies, case histories - The knowledge: investigations and monitoring - Seismic risk, site effects, soil structure interaction - Effects of urban development and tunnelling on built heritage - Preservation of diffuse heritage: soil instability, subsidence, environmental damages The present volume aims at geotechnical engineers and academics involved in the preservation of monuments and historic sites worldwide

Evaluation of new technologies to support asset management of metro systems

Since 1930, London Underground Limited (LUL) has performed visual inspections to understand the condition of the physical assets such as tunnels, bridges and structures. The major problem with this kind of inspection is the lack in quality of the data, as it depends on the ability of the inspector to assess and interpret the condition of the asset both accurately and with repeatability. In addition, data collection is time-consuming and, therefore, costly when the whole of the metro network needs to be regularly inspected and there are limited periods when access is available. The problems associated with access to the infrastructure have increased significantly with the implementation of the night tube and will increase further as the night tube is extended over the next 5 to 10 years. To determine the condition of metro assets and to predict the need for intervention, monitoring the changes in the assets’ condition is key to any further evaluation and maintenance planning. This thesis presents the outcomes of using new technologies such as Thermography, Kinematic and Static Laser Scanning, Close-Range Photogrammetry and Total Station to measure defects, such as water seepage, mortar loss in joints, lining face loss (in brick tunnels), cracks, corrosion, voids, cavities and spalls. Each technique is explored through three case studies that evaluate the performance and limitation in the determination of the asset condition. The first case study was performed to compare and contrast the use of Euroconsult’s high definition laser survey against a Principal Inspection Report to determine the level of consistency in predicting the asset condition. During this case study, reports from laser surveys and principal inspections of brick tunnels and covered ways were compared. This analysis showed that a direct comparison between the two inspections is not appropriate because the laser inspection does not capture all the defects mentioned in the Engineering Standard S1060. It also showed that to close the gap between the laser survey and visual inspection, laser surveys would have to be performed every year in brick tunnels and then compare any changes in asset condition with that from the previous scan. The second case study was performed using Infrared Thermography (IRT) to identify water seepage in the brick tunnels as well as test the system in a configuration that would allow the survey to be done from an engineering train. A set of calibration tests were performed in the lab and later the technique was trialled on an engineering train. The results showed that it is possible to measure the level of moisture on specific parts of the lining and that the comparison of surveys performed at different times can allow asset managers to react before a seepage is established, potentially reducing the risk of system disruption caused by water ingress in tunnels. The data also revealed that this technique could be used for other purposes, such as examining the condition of other assets such as brackets, cable supports and broken light bulbs. The third case study was performed using a Terrestrial Laser Scanner, Close-Range Photogrammetry and Total Station Survey to identify defects in structures. In order to test these technologies, a wing wall, located on the north-east wing of the HC3 underbridge at Ladbroke Grove Station, was chosen. This case study demonstrated that LUL can easily implement this type of technology to inspect rapidly their buildings and structures, being able to identify defects and monitor their assets for translation, rotation and changes in shape during changes in loading or the decay of the structure (insidious decline) and the construction of nearby assets. In this research, a large volume of data was captured, and further work is needed in order to manage the data using ‘big data’ concepts. Although it may not be possible to fully understand the insidious decline of an asset, the use of these techniques allows us to better understand how a civil asset behaves, potentially reducing the amount of reactive maintenance to a minimum, consequently reducing service costs and falls in revenue due to disruptions in the system. To successfully analyse the data from new technologies a combination of skills is required and different or retrained personal will be needed

Fiscal Year 1999

The Department of Energy (DOE) and its predecessors have conducted research and development (R&D) in geothermal energy since 1971. To develop the technology needed to harness the Nation's vast geothermal resources, DOE's Office of Geothermal and Wind Technologies oversees a network of national laboratories, industrial contractors, universities, and their subcontractors. The following mission and goal statements guide the overall activities of the Office of Geothermal and Wind Technologies. This Federal Geothermal Program Research Update reviews the specific objectives, status, and accomplishments of DOE's Geothermal Program for Federal Fiscal Year (FY) 1999. The information contained in this Research Update illustrates how the mission and goals of the Office of Geothermal and Wind Technologies are reflected in each R&D activity. The Geothermal Program, from its guiding principles to the most detailed research activities, is focused on expanding the use of geothermal energy