scholarly journals A DOFS-Based Approach to Calculate the Height of Water-Flowing Fractured Zone in Overlying Strata under Mining

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Chunde Piao ◽  
Jinjun Li ◽  
Dangliang Wang ◽  
Wei Qiao
Keyword(s):  
Shear Stress ◽  
Optical Fiber ◽  
Model Test ◽  
Coal Mine ◽  
Fiber Sensors ◽  
Fractured Zone ◽  
Geological Conditions ◽  
Seam Mining ◽  
Distributed Optical Fiber ◽  
Overlying Strata

The distributed optical fiber sensing (DOFS) is a technique that can obtain full spatial and temporal information concerning the behavior of a large range of measurand fields along a fiber path and realize the distributed monitoring of the overburden section under mining. To calculate the height of water-flowing fractured zone caused by the exploitation of coal, this study employed distributed optical fiber sensors with OSI-C-S optical frequency domain reflectometry (OFDR) technology and designed a similar-material model test based on the engineering geological conditions of Daliuta Coal Mine. Through the test, deformation characteristics of overlying strata were studied, the linear relationship was summarized between the strain gradient and the shear stress measured by fiber sensors when the rock layer cracks, and a method was proposed of using the measured strain to measure the height of the water-flowing fractured zone in overlying strata. The test results show that there are several locations where the sign of the shear stress changes (positive to negative or vice versa) in the overlying strata during the initial stage of coal seam mining. As the working face advanced, the change locations gradually concentrated at the place where the rock cracks. By identifying the breakpoints of the rock and the locations where the sign of the shear stress measured by fiber sensors changes, this paper calculated the height of the water-flowing fractured zone in Daliuta Coal Mine. After comparing the height with the abscission layer position in the model test and the predicted height by the empirical formulas in the specification, it has been found that the three results are basically consistent, which in turn verifies the accuracy of this method.

scholarly journals Study of the Fracture Law of Overlying Strata under Water Based on the Flow-Stress-Damage Model

Geofluids ◽  
2019 ◽  
Vol 2019 ◽  
pp. 1-12 ◽  
Author(s):  
Zhijie Wen ◽  
Suolin Jing ◽  
Yujing Jiang ◽  
Lei Tian ◽  
Jinhao Wen ◽  
...  
Keyword(s):  
Flow Stress ◽  
Coal Mine ◽  
Damage Model ◽  
Test System ◽  
Laboratory Simulation ◽  
Fractured Zone ◽  
Working Face ◽  
Geological Conditions ◽  
Stress Damage ◽  
Overlying Strata

To accurately detect the development height of the water flowing fractured zone (WFFZ) in the overlying strata of the working face after mining under water and to ensure the safety and reliability of coal mining, the coal seam located under Weishanhu Lake in the Jisan coal mine was used as the experimental system. A similar laboratory simulation and water injection-based fracturing test system were used with the working face before and after mining activity to calculate, quantitatively detect, and qualitatively analyze the development height of the WFFZ in the overlying strata. Meanwhile, a flow-stress-damage model and its criterion of fracture expansion were established based on the Mohr-Coulomb criterion, and the FLAC 3D software was used to simulate the deformation and failure of the overlying strata and the evolution of WFFZ during the mining process. The results showed that the height ranges of the WFFZ beneath Weishanhu Lake of the Jisan coal mine as established by the above three methods are 30-45 m, 30-48 m, and 30-50 m. In the process of mining, the caving zone and fractured zone are, respectively, subjected to tensile failure and shear failure. The development height of the water flowing through the fractured zone in the overlying strata is basically consistent with the range of the “breaking arch.” The flow-stress-damage model and its criterion of fracture expansion can be applied to the fracture law of overlying strata under water under similar geological conditions.

scholarly journals A Review of Recent Distributed Optical Fiber Sensors Applications for Civil Engineering Structural Health Monitoring

Sensors ◽  
2021 ◽  
Vol 21 (5) ◽  
pp. 1818
Author(s):  
Mattia Francesco Bado ◽  
Joan R. Casas
Keyword(s):  
Structural Health Monitoring ◽  
Optical Fiber ◽  
Health Monitoring ◽  
Optical Fiber Sensors ◽  
Vibration Monitoring ◽  
Fiber Sensors ◽  
Structural Health ◽  
Comprehensive Collection ◽  
Monitoring Tools ◽  
Distributed Optical Fiber

The present work is a comprehensive collection of recently published research articles on Structural Health Monitoring (SHM) campaigns performed by means of Distributed Optical Fiber Sensors (DOFS). The latter are cutting-edge strain, temperature and vibration monitoring tools with a large potential pool, namely their minimal intrusiveness, accuracy, ease of deployment and more. Its most state-of-the-art feature, though, is the ability to perform measurements with very small spatial resolutions (as small as 0.63 mm). This review article intends to introduce, inform and advise the readers on various DOFS deployment methodologies for the assessment of the residual ability of a structure to continue serving its intended purpose. By collecting in a single place these recent efforts, advancements and findings, the authors intend to contribute to the goal of collective growth towards an efficient SHM. The current work is structured in a manner that allows for the single consultation of any specific DOFS application field, i.e., laboratory experimentation, the built environment (bridges, buildings, roads, etc.), geotechnical constructions, tunnels, pipelines and wind turbines. Beforehand, a brief section was constructed around the recent progress on the study of the strain transfer mechanisms occurring in the multi-layered sensing system inherent to any DOFS deployment (different kinds of fiber claddings, coatings and bonding adhesives). Finally, a section is also dedicated to ideas and concepts for those novel DOFS applications which may very well represent the future of SHM.

Reasonable Entry Layout of Lower Seam in Multi-Seam Mining Based on Numerical Simulation

2013 ◽  
Vol 295-298 ◽  
pp. 2980-2984
Author(s):  
Xiang Qian Wang ◽  
Da Fa Yin ◽  
Zhao Ning Gao ◽  
Qi Feng Zhao
Keyword(s):  
Numerical Simulation ◽  
Stress Distribution ◽  
Coal Seam ◽  
Coal Mine ◽  
Abutment Pressure ◽  
Surrounding Rock ◽  
Geological Conditions ◽  
Seam Mining

Based on the geological conditions of 6# coal seam and 8# coal seam in Xieqiao Coal Mine, to determine reasonable entry layout of lower seam in multi-seam mining, alternate internal entry layout, alternate exterior entry layout and overlapping entry layout were put forward and simulated by FLAC3D. Then stress distribution and displacement characteristics of surrounding rock were analyzed in the three ways of entry layout, leading to the conclusion that alternate internal entry layout is a better choice for multi-seam mining, for which makes the entry located in stress reduce zone and reduces the influence of abutment pressure of upper coal seam mining to a certain extent,. And the mining practice of Xieqiao Coal Mine tested the results, which will offer a beneficial reference for entry layout with similar geological conditions in multi-seam mining.

scholarly journals Frequency Resolution Quantification of Brillouin-Distributed Optical Fiber Sensors

2016 ◽  
Vol 28 (21) ◽  
pp. 2367-2370 ◽  
Author(s):  
Yifei Yu ◽  
Linqing Luo ◽  
Bo Li ◽  
Kenichi Soga ◽  
Jize Yan
Keyword(s):  
Optical Fiber ◽  
Optical Fiber Sensors ◽  
Frequency Resolution ◽  
Fiber Sensors ◽  
Distributed Optical Fiber

scholarly journals Modeling and evaluating the performance of Brillouin distributed optical fiber sensors

2013 ◽  
Vol 21 (25) ◽  
pp. 31347 ◽  
Author(s):  
Marcelo A. Soto ◽  
Luc Thévenaz
Keyword(s):  
Optical Fiber ◽  
Optical Fiber Sensors ◽  
Fiber Sensors ◽  
Distributed Optical Fiber

scholarly journals Fast Measurement of Brillouin Frequency Shift in Optical Fiber Based on a Novel Feedforward Neural Network

Photonics ◽  
2021 ◽  
Vol 8 (11) ◽  
pp. 474
Author(s):  
Fen Xiao ◽  
Mingxing Lv ◽  
Xinwan Li
Keyword(s):  
Neural Network ◽  
Optical Fiber ◽  
Frequency Shift ◽  
Brillouin Scattering ◽  
Principal Component ◽  
Feedforward Neural Network ◽  
Gain Spectrum ◽  
Fiber Sensors ◽  
Brillouin Gain ◽  
Distributed Optical Fiber

Brillouin scattering-based distributed optical fiber sensors have been successfully employed in various applications in recent decades, because of benefits such as small size, light weight, electromagnetic immunity, and continuous monitoring of temperature and strain. However, the data processing requirements for the Brillouin Gain Spectrum (BGS) restrict further improvement of monitoring performance and limit the application of real-time measurements. Studies using Feedforward Neural Network (FNN) to measure Brillouin Frequency Shift (BFS) have been performed in recent years to validate the possibility of improving measurement performance. In this work, a novel FNN that is 3 times faster than previous FNNs is proposed to improve BFS measurement performance. More specifically, after the original Brillouin Gain Spectrum (BGS) is preprocessed by Principal Component Analysis (PCA), the data are fed into the Feedforward Neural Network (FNN) to predict BFS.

Modal Analysis of Turbine Blades by Means of Distributed Optical Fiber Sensors

2020 ◽  
Author(s):  
Paolo Pennacchi ◽  
Gabriele Cazzulani ◽  
Alejandro Silva
Keyword(s):  
Optical Fiber ◽  
Modal Analysis ◽  
Turbine Blade ◽  
Turbine Blades ◽  
Optical Fiber Sensors ◽  
Operating Conditions ◽  
Fiber Sensors ◽  
Steam Turbine Blade ◽  
3D Printed ◽  
Distributed Optical Fiber

Abstract This paper investigates the possibility of identifying and monitoring the modal shapes of a turbine blade by means of continuous optical fiber sensors based on Optical Backscatter Reflectometry (OBR). The advantage of this approach would be the possibility of embedding the sensors in future carbon fiber blades, in order to make this modal analysis approach available also for the blade operating conditions, since no modifications in the blade fluid-structure interaction occur. The paper describes the proposed method and provides some experimental results obtained on a 3D printed model of an existing steam turbine blade.

Optical fiber sensors for coal mine shaft integrity and equipment condition monitoring

2019 ◽  
Author(s):  
Feng Zhu ◽  
Gonghua Wang ◽  
Tongyu Liu ◽  
Gang Ma ◽  
Kenneth T. V. Grattan ◽  
...  
Keyword(s):  
Optical Fiber ◽  
Condition Monitoring ◽  
Coal Mine ◽  
Optical Fiber Sensors ◽  
Mine Shaft ◽  
Fiber Sensors

scholarly journals Crack monitoring in reinforced concrete beams by distributed optical fiber sensors

2020 ◽  
Vol 17 (1) ◽  
pp. 124-139 ◽  
Author(s):  
Carlos G. Berrocal ◽  
Ignasi Fernandez ◽  
Rasmus Rempling
Keyword(s):  
Reinforced Concrete ◽  
Optical Fiber ◽  
Concrete Beams ◽  
Optical Fiber Sensors ◽  
Reinforced Concrete Beams ◽  
Fiber Sensors ◽  
Crack Monitoring ◽  
Distributed Optical Fiber
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