scholarly journals Stability Assessment of Mining Excavations: the Impact of Large Depths

2018 ◽  
Vol 40 (3) ◽  
pp. 180-187
Author(s):  
Tadeusz Majcherczyk ◽  
Zbigniew Niedbalski ◽  
Łukasz Bednarek
Keyword(s):  
Rock Mass ◽  
In Situ Monitoring ◽  
Stability Assessment ◽  
Underground Excavations ◽  
Deformation Prediction ◽  
Large Depth ◽  
Coal Deposits ◽  
The Impact

AbstractBack in the early 1980s, coal deposits occurring at depths of ~700 m below surface were already regarded as large-depth deposits. Meanwhile, today the borderline depth of large-depth mining has extended to >1,000 m. Design, excavation and maintenance of mining roadways at the depth of >1,000 m have, therefore, become crucial issues in a practical perspective in recent years. Hence, it is now extremely important to intensify research studies on the influence of large depths on the behaviour of rock mass and deformation of support in underground excavations. The paper presents the results of the study carried out in five mining excavations at depths ranging from 950 to 1,290 m, where monitoring stations with measurement equipment were built. The analysis of data from laboratory and coal mine tests, as well as in situ monitoring, helped to formulate a set of criteria for stability assessment of underground excavations situated at large depths. The proposed methodology of load and deformation prediction in support systems of the excavations unaffected by exploitation is based on the criteria referring to the depth of excavation and the quality of rock mass. The depth parameter is determined by checking whether the analysed excavation lies below the critical depth, whereas the rock mass quality is determined on the basis of the roof lithology index (WL) and the crack intensity factor (n)

Nanostructure Growth Supported by In Situ RHEED Evaluation

2017 ◽  
Vol 885 ◽  
pp. 234-238
Author(s):  
Péter Kucsera ◽  
Tamás Sándor ◽  
Gusztáv Varga Tényi ◽  
Márton Csutorás ◽  
Gergely Bátori ◽  
...  
Keyword(s):  
Growth Kinetics ◽  
In Situ Monitoring ◽  
Nanostructure Formation

The in-situ monitoring of the MBE grown nanostructures can be carried out using the RHEED method. During the droplet epitaxal growth, the observation of the nanostructure formation is very important to understand the growth kinetics. In the present work, a novel in-situ RHEED evaluation and further MBE related developments are introduced, with which the quality of the nanostructure preparation can be improved.

Study on Deformation and Damage of Rock Mass Subject to High In Situ Stress by Using a Elastoplastic Damage Model and Considering the Impact of Weak Planes

2013 ◽  
Vol 838-841 ◽  
pp. 705-709
Author(s):  
Yun Hao Yang ◽  
Ren Kun Wang
Keyword(s):  
Rock Mass ◽  
Large Scale ◽  
Damage Model ◽  
Back Analysis ◽  
In Situ Stress ◽  
Surrounding Rock ◽  
High In Situ Stress ◽  
Underground Caverns ◽  
The Impact

Large scale underground caverns are under construction in high in-situ stress field at Houziyan hydropower station. To investigate deformation and damage of surrounding rock mass, a elastoplastic orthotropic damage model capable of describing induced orthotropic damage and post-peak behavior of hard rock is used, together with a effective approach accounting for the presence of weak planes. Then a displacement based back analysis was conducted by using the measured deformation data from extensometers. The computed displacements are in good agreement with the measured ones at most of measurement points, which confirm the validities of constitutive model and numerical simulation model. The result of simulation shows that damage of surrounding rock mass is mainly dominated by the high in-situ stress rather than the weak planes and heavy damage occur at the cavern shoulders and side walls.

Study on Support of Roadways in Fractured Rock Mass under Mining-Induced Stresses

2013 ◽  
Vol 807-809 ◽  
pp. 2332-2339
Author(s):  
Qiang Wang ◽  
Jin Yu Chen
Keyword(s):  
Rock Mass ◽  
Abutment Pressure ◽  
Underground Mining ◽  
Fractured Rock ◽  
The State ◽  
In Situ Monitoring ◽  
Initial Stresses ◽  
Induced Stresses ◽  
The Stability

One of the difficult issues in underground mining is the ground control of roadway subject to mining induced stresses. As a longwall face advances, the state of initial stresses dramatically changes. Accordingly, lateral abutment pressure forms on the pillar and frontal abutment pressure on the roof and lateral sides of the roadway. These pressures will lead to severe deformation and deterioration of the rock mass surrounding the entries. In this paper, a systemic study on this issue is proposed using the combination of numerical modeling and in-situ monitoring which was carried out at a coal mine in the Lu.An Group, China. The condition of stress redistribution caused by mining-induced stresses and the state of the surrounding rock mass of the roadway situated in front the work face are systematically investigated. Different patterns of support and reinforcement as well as their effects on the stability of the roadway are also presented.

Comparative Study on in-situ Ellipsometric Monitoring of III-Nitride Film Growth via Plasma-Enhanced Atomic Layer Deposition

2019 ◽  
Vol 28 (03n04) ◽  
pp. 1940020
Author(s):  
Adnan Mohammad ◽  
Deepa Shukla ◽  
Saidjafarzoda Ilhom ◽  
Brian Willis ◽  
Ali Kemal Okyay ◽  
...  
Keyword(s):  
Growth Rate ◽  
Real Time ◽  
Film Growth ◽  
Atomic Layer ◽  
Layer Growth ◽  
In Situ Monitoring ◽  
Rf Plasma ◽  
Nitride Film ◽  
The Impact

In this paper a comparative in-situ ellipsometric analysis is carried out on plasma-assisted ALD-grown III-nitride (AlN, GaN, and InN) films. The precursors used are TMA, TMG, and TMI for AlN, GaN, and InN respectively, while Ar is used as purge gas. For all of the films N2/H2/Ar plasma was used as the co-reactant. The work includes real-time in-situ monitored saturation curves, unit ALD cycle analysis, and >500 cycle film growth runs. In addition, the films are grown at different substrate temperatures to observe the impact of temperature not only on the growth rate but on how it influenced the precursor chemisorption, ligand removal, and nitrogen incorporation surface reactions. All three nitride films confirm fairly linear growth character. The growth rate per cycle (GPC) for each film is also measured with respect to rf-plasma power to obtain the surface saturation conditions during ALD growth. The real-time in-situ monitoring of the film growth can really be beneficial to understand the atomic layer growth and film formation in each individual ALD cycle.

scholarly journals CO2 Concentration and Occupants’ Symptoms in Naturally Ventilated Schools in Mediterranean Climate

Buildings ◽  
2019 ◽  
Vol 9 (9) ◽  
pp. 197 ◽  
Author(s):  
Jesica Fernández-Agüera ◽  
Miguel Ángel Campano ◽  
Samuel Domínguez-Amarillo ◽  
Ignacio Acosta ◽  
Juan José Sendra
Keyword(s):  
Mediterranean Climate ◽  
Co2 Concentration ◽  
Building Envelope ◽  
In Situ Monitoring ◽  
Building Stock ◽  
Air Infiltration ◽  
The Mean ◽  
The Impact ◽  
Different Levels

A large part of the school building stock in Andalusia lacks ventilation facilities, so that the air renewal of the classrooms is achieved through the building envelope (air infiltration) or the opening of windows. This research analyses the airtightness of the classrooms in Andalusia and the evolution of CO2 concentration during school hours through in situ monitoring. Pressurization and depressurization tests were performed in 42 classrooms and CO2 concentration was measured in two different periods, winter and midseason, to study the impact of the different levels of aperture of windows. About 917 students (11–17 years of age) were surveyed on symptoms and effects on their health. The mean n50 values are about 7 h−1, whereas the average CO2 concentration values are about 1878 ppm, with 42% of the case studies displaying concentrations above 2000 ppm with windows closed.

scholarly journals Framework for the Simulation of Sensor Networks Aimed at Evaluating In Situ Calibration Algorithms

Sensors ◽  
2020 ◽  
Vol 20 (16) ◽  
pp. 4577
Author(s):  
Florentin Delaine ◽  
Bérengère Lebental ◽  
Hervé Rivano
Keyword(s):  
Sensor Networks ◽  
Sensor Network ◽  
Low Cost ◽  
Test Case ◽  
Dense Networks ◽  
In Situ Calibration ◽  
Primary Test ◽  
The Impact

The drastically increasing availability of low-cost sensors for environmental monitoring has fostered a large interest in the literature. One particular challenge for such devices is the fast degradation over time of the quality of their data. Therefore, the instruments require frequent calibrations. Traditionally, this operation is carried out on each sensor in dedicated laboratories. This is not economically sustainable for dense networks of low-cost sensors. An alternative that has been investigated is in situ calibration: exploiting the properties of the sensor network, the instruments are calibrated while staying in the field and preferably without any physical intervention. The literature indicates there is wide variety of in situ calibration strategies depending on the type of sensor network deployed. However, there is a lack for a systematic benchmark of calibration algorithms. In this paper, we propose the first framework for the simulation of sensor networks enabling a systematic comparison of in situ calibration strategies with reproducibility, and scalability. We showcase it on a primary test case applied to several calibration strategies for blind and static sensor networks. The performances of calibration are shown to be tightly related to the deployment of the network itself, the parameters of the algorithm and the metrics used to evaluate the results. We study the impact of the main modelling choices and adjustments of parameters in our framework and highlight their influence on the results of the calibration algorithms. We also show how our framework can be used as a tool for the design of a network of low-cost sensors.

Towards Remote Sensing of Atmospheric Trace Gases in the UV spectral range using Dual-Comb spectroscopy

2021 ◽  
Author(s):  
Clément Pivard ◽  
Sandrine Galtier ◽  
Patrick Rairoux
Keyword(s):  
Remote Sensing ◽  
Spectral Range ◽  
Near Infrared ◽  
Frequency Comb ◽  
Trace Gases ◽  
In Situ Monitoring ◽  
Atmospheric Trace Gases ◽  
The Impact ◽  
Uv Range

<p>The development of increasingly sensitive and robust instruments and new methodologies are essential to improve our understanding of the Earth’s climate and air pollution. In this context, Dual-Comb spectroscopy (DCS) appears as an emerging spectroscopy methodology to detect in situ, without air-sampling, atmospheric trace-gases.</p><p>DCS is a Fourier-transform type experiment that takes advantage of mode-locked femtosecond (fs) pulses. This methodology appears highly relevant for atmosphere remote-sensing studies because of its very fast acquisition rate (>kHz) that reduces the impact of atmospheric turbulences on the retrieved spectra. DCS has been successfully applied in near-infrared (NIR) spectral ranges for atmospheric greenhouse gas monitoring (water vapor, carbon dioxide, and methane) [1-2].</p><p>Its implementation in the UV range would offer a new spectroscopic intrumentation to target the most reactive species of the atmosphere (OH, HONO, BrO...) as they have their greatest absorption cross-sections in the UV range. UV-DCS would therefore be an answer to the lack of variability of today operationnal and in situ monitoring instrument for those reactive molecules.</p><p>We will present a potential light source for remote sensing UV-DCS and discuss the degree of immunity of UV-DCS to atmospheric turbulences. We will show to which extent the characteristics of the currently available UV sources are compatible with the unambiguous identification of UV absorbing gases by UV-DCS. We will finally present the performances of UV-DCS in terms of concentration detection limit for several UV absorbing molecules (OH, BrO, NO<sub>2</sub>, OClO, HONO, CH<sub>2</sub>O, SO<sub>2</sub>). This sensitivity study has been recently published [3] and the main results will be presented.</p><p> </p><p>[1] Rieker, G.B.; Giorgetta, F.R.; Swann, W.C.; Kofler, J.; Zolot, A.M.; Sinclair, L.C.; Baumann, E.; Cromer, C.;Petron, G.; Sweeney, C.; et al. « Frequency-comb-based remote sensing of greenhouse gases over kilometer air Paths ». Optica 1, p. 290–298 (2014)</p><p>[2] Oudin, J.; Mohamed, A.K.; Hébert, P.J. "IPDA LIDAR measurements on atmospheric CO2 and H2O using dual comb spectroscopy," Proc. SPIE 11180, International Conference on Space Optics — ICSO 2018, p. 111802N (12 July 2019)</p><p>[3] Galtier, S.; Pivard, C.; Rairoux, P. Towards DCS in the UV Spectral Range for Remote Sensing of Atmospheric Trace Gases. Remote Sens., 12, p.3444 (2020)</p>

scholarly journals Methods Applied in the Prediction of Brittle Failure in Tunnels and Underground Caverns

2018 ◽  
Vol 22 ◽  
pp. 5-9
Author(s):  
Krishna Kanta Panthi
Keyword(s):  
Rock Mass ◽  
Rock Burst ◽  
Brittle Failure ◽  
In Situ Stress ◽  
Rock Cover ◽  
Underground Caverns ◽  
Rock Burst Prediction ◽  
Stress Environment

Tunnels and underground caverns located at greater depth (high rock cover or overburden) are subjected to high in-situ stress environment. Those rock mass that are relatively unjointed and massive are exposed to the brittle failure, which is famously known as rock spalling/ rock bursting phenomenon. Establishing state of the stress and evaluating stress-induced instability in tunnels passing through such rock mass at relatively greater depth is therefore a challenge. The aim of this manuscript is to describes existing brittle failure (rock burst) prediction methods that are being practiced worldwide and propose necessary editions so that quality of assessment is enhanced. The methods described are very practical and the author is confident that professional engineers will use them to evaluate and predict potential rock burst/ rock spalling scenario in the tunnels during planning, design and construction phases. Each method of prediction is explained, applicability extent is highlighted and comparisons between the methods are made.  HYDRO Nepal JournalJournal of Water Energy and EnvironmentIssue No: 22Page: 5-9Uploaded date: January 14, 2018

Online Prediction and Verification of Cured Quality of Advanced Composites in Autoclave Process

2016 ◽  
Vol 703 ◽  
pp. 3-10
Author(s):  
Yong An Zhang ◽  
Li Hua Zhan
Keyword(s):  
In Situ Monitoring ◽  
Metallographic Analysis ◽  
Resin Flow ◽  
Composite Part ◽  
Monitoring Method ◽  
Verification Method ◽  
Part Quality ◽  
Ultrasonic Phased Array

The strain in curing process of composite part would be influenced by curing compaction, resin flow, curing action and tool-part interaction, meanwhile these factors would also influence the final cured quality of composite part. In this paper, FBG(fiber Bragg grating) sensors are used to in-situ monitoring the strain of composite parts, which are cured in four different pressure situation by autoclave: 0.0Mpa,0.2Mpa,0.4Mpa,0.6MPa. by analyzing the strain change rule, the part quality is predicted, then the predictive result is compared with some verification method: measurement of part’s boundary dimension, ultrasonic phased array scanning, metallographic analysis. The result shows that, the prediction is consistent with verification, the in-situ monitoring method by using FBG sensor is available for predicting cured quality of composite parts accurately: increase curing pressure is benefit of part compaction, resin flow, and reduce delamination,pores in composite part, finally improving the part quality dramatically.

Sign in / Sign up

Export Citation Format

Share Document