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Abstract

In 2017, the Central Mining Institute (GIG), Jastrzębska Spółka Węglowa SA (JSW SA), the largest producer of coking coal in Europe, and JOY KOMATSU, the producer of mining machinery, signed a consortium. The project’s main goal was to reduce the costs of driving mine workings by reintroducing the rock bolt support. The works began in November 2019, and for the first time in the history of Polish coal mining, a Bolter Miner machine was used for the purpose. The paper presents the results of measuring the axial forces in rock bolts at the measurement base and their analysis with numerical modelling.
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Bibliography

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[2] S . Banerjee, Performance evaluation of continuous miner based underground mine operation system: An OEE based approach. New Trends in Production Engineering 2, 1, 596-603 (2019). DOI: https://doi.org/10.2478/ntpe-2019-0065
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[6] I . Canbulat, A. Wilkinson, G. Prohaska, M. Mnisi, N. Singh, An investigation into the support systems in South African collieries. Safety in Mines Research Advisory Committee, Project No SI M 020205, CSIR Division of Mining Technology, Ground Consulting (Pty) Ltd (2005).
[7] C . Cao, PhD thesis, Bolt profile configuration and load transfer capacity optimisation. School of Civil, Mining and Environmental Engineering, University of Wollongong (2012).
[8] D .R. Dolinar, S.K. Bhatt, Trends in roof bolt application. Proceedings: new technology for coal mine roof support. C. Mark, D.R. Dolinar, R.J. Tuchman, T.M. Barczak, S.P. Signer, P.F. Wopat, (Eds.) Cincinnati, OH: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication No. 2000-151 (IC 9453), 43-51 (2000).
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[13] H. Jalalifar, PhD thesis, A new approach in determining the load transfer mechanism in fully grouted bolts. School of Civil, Mining and Environmental Engineering, University of Wollongong (2006).
[14] H. Jurecka, Ankerausbau eine Schlüsseltechnologie für Hochleistungsstrebbetriebe in großen Teufen. Aachen International Mining Symposia, 4th International Symposium – Roofbolting in Mining, RWTH Aachen, 1-17 (2001).
[15] V. Kajzar, R. Kukutsch, P. Waclawik, P. Konicek, Coal pillar deformation monitoring using terrestrial laser scanner technology in room and pillar panel – A case study from the Ostrava-Karvina Coal Field. Rock Mechanics and Rock Engineering: From the Past to the Future – Ulusay et al. (Eds.), Taylor & Francis Group, London, 951-956 (2016).
[16] H. Kang, Support technologies for deep and complex roadways in underground coal mines: a review. Int. J. Coal Sci. Technol. 1 (3), 261-277 (2014). DOI: https://doi.org/10.1007/s40789-014-0043-0
[17] H. Kang, Sixty years development and prospects of rock bolting technology for underground coal mine roadways in China. Journal of China University of Mining & Technology 45 (6), 1071-1081 (2016).
[18] K . Kovári, The Control of Ground Response – Milestones up to the 1960s. Proc. of the AITES -ITA World Tunnel Congress, Italy, Milan, 93-119 (2001).
[19] A . Kumar, R. Singh, P. Waclawik, Numerical Modelling Based Investigation of Coal Pillar Stability for Room and Pillar Development at 900 m Depth of Cover. 37TH International Conference on Ground Control in Mining, 193-203 (2018).
[20] B. Langhanki, Planungskonzeption zur Doppelnutzung einer Rechtankerstrecke im Flöz D2/C in 1.200 m Teufe. Aachen International Mining Symposia, 4th International Symposium – Roofbolting in Mining, RWTH Aachen, 217-233 (2001).
[21] J. Luo, PhD thesis, A New Rock Bolt Design Criterion and Knowlwdge-based Expert System for Stratified Roof. Faculty of the Virginia Polytechnic Institute and State University, Blacksburg, Virginia (1999).
[22] T . Majcherczyk, A. Szaszenko, E. Sdżwiżkowa, Fundamentals of geomechanics. Wydawnictwo AGH, Kraków (2006).
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[24] C . Mark, Design of roof bolt systems. Proc.New Technology For Coal Mine Roof Support. U.S. Department of Health and Human Services, Pittsburgh, PA, 111-131 (2000).
[25] J. Modi, S. Bharti, R. Kant, Applicability of Continuous Miner in Room and Pillar Mining System: Higher Production and Productivity with Safety. International Conference on Deep Excavation, Energy Resource and Production (DEE P16), IIT Kharagpur, India (2017).
[26] A . Nierobisz, Rockbolting – history, present and future. Międzynarodowa Konferencja Szkoleniowa: Perspektywy stosowania obudowy kotwowej w polskich kopalniach węgla kamiennego, Jaworze, kwartalnik GIG Nr 2/1/2010, 184-203 (2010).
[27] A . Nierobisz, Development of Roof Bolting Use in Polish Coal Mines. Journal of Mining Science 47, No. 6, 751- 760 (2011).
[28] B. Neyman, R. Gocman, Guidelines for rockbolt support in workings. Biuletyn techniczno-informacyjny GIG nr 9 (1960).
[29] K. Opolony, H. Witthaus, A. Hucke, A. Studeny, Ergebnisse von numerischen Berechnungen und physikalischen Modellversuchen als Planungshilfe für eine Rechteckankerstrecke in Flöz D2/C. Aachen International Mining Symposia, 5th International Symposium – Roofbolting in Mining, RWTH Aachen, 539-554 (2004).
[30] S. Peng, Coal Mine Ground Control. (3rd ed.), Syd Peng Publisher, Morgantown (2008).
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[33] E.U. Reuther, A. Heime, Verbesserte Bemessung von Ankerausbau in Abbau- und Basisstrecken. Kommission der Europäischen Gemeinschaften, technische Forschung Kohle, Forschungsvertrag Nr. 7220-AB/120, Luxemburg (1990).
[34] A. Sahebi, J. Hossein, M. Ebrahimi, Stability analysis and optimum support design of a roadway in a faulted zone during longwall face retreat – case study: Tabas Coal Mine. N. Aziz (Eds.), 10th Underground Coal Operators’ Conference, University of Wollongong & the Australasian Institute of Mining and Metallurgy, 88-96 (2010).
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Authors and Affiliations

Wojciech Masny
1
ORCID: ORCID
Łukasz Nita
2
ORCID: ORCID
Jerzy Ficek
3

  1. Central Mining Institute, 1 Gwarków Sq., 40-166 Katowice, Poland
  2. Jastrzębska Spółka Węglowa SA, KWK „Budryk”, Poland
  3. „Geofic“ Scientific and Technical Office, Poland
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Abstract

The assessment of a rock’s behaviour around excavations and the effectiveness of its reinforcement in underground ore mines is dependent on the performance of the rock-bolt and rock-mass interaction, which can be estimated on the basis of appropriately designed measurements. Based on the background of various measurements solutions described in the literature, concerning rock bolt monitoring methods, the authors proposed a new, original device for mass measurements in mine conditions. After examining the advantages and disadvantages of existing constructions, the article presents the essence, principle of operation and method of measuring anchor load in an underground excavation with the a instrument, indicator WK-2/8. The prototype has been carefully researched and successfully tested in a full-scale laboratory environment. This instrument, also referred to as a load indicator or force pad, does not require electrical power and allows for relatively accurate (with a resolution of 10-14kN, up to about 90kN loading capacity) and a remote reading of the axle loading of the anchor (AGH patent) by any person present in the specified area. The device can be installed in mining excavations under loading conditions. The relatively low cost of a measuring instrument, practically used as an additional washer, as well as an easy assembly method, makes it universally applicable in mines where anchoring is used as a means of strengthening the rock.

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Authors and Affiliations

Waldemar Korzeniowski
Krzysztof Skrzypkowski
Łukasz Herezy
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Abstract

The hydrogen embrittlement of metals is caused by the penetration and accumulation of hydrogen atoms inside the metal. The failure of the product due to hydrogen embrittlement is delayed in time and does not occur immediately after its manufacture, but several hours, days, or even weeks later. Therefore, the chances of detecting hydrogen embrittlement when checking the quality of the finished product are very slim. The use of high-strength bolts in industry is associated with the risk of hydrogen embrittlement. This phenomenon poses a threat to the safe use of devices by limiting or completely losing the functionality of the bolt joint. Even a low influence of moisture can trigger failure mechanisms.
The article proposes a method for assessing the risk of hydrogen embrittlement for high-strength bolts in class12.9. For this purpose, bolts made of material grade 32CrB4 were prepared and in a controlled manner the grain flow inconsistency was made, leading in extreme cases to the production of the forging lap. To perform the study, the device proposed by the European Assessment Document (EAD) was adapted to the testing of hydrogen embrittlement of threaded fasteners in concrete. The concrete substrate was replaced with metal spacers that were preloaded with a bolt. The use of the wedge distance under the bolt head led to the generation of two stress states – tensile and compressive, which translated into an increased risk of hydrogen embrittlement. After being tested, the bolts were visually and microscopically inspected to assess potential locations for cracks and hydrogen propagation. As a result of the conducted tests, it was found that the prepared test method allows to assess the resistance or susceptibility of the bolt to threats related to hydrogen embrittlement.
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Authors and Affiliations

T. Dubiel
1
ORCID: ORCID
T. Balawender
2
ORCID: ORCID
M. Osetek
1
ORCID: ORCID

  1. Koelner Rawlplug IP Sp. z o.o. Oddział w Łańcucie, Rzeszów University of Technology
  2. Rzeszów University of Technology, Departament of Materials Forming and Processing, 12 Powstańców Warszawy Av., 35-959 Rzeszów, Poland
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Abstract

The use of cold forging is a widely used solution in many industries. One application is the manufacture of bolts and fasteners. The largest amounts of bolts are used in the automotive and machine industry. Those customers demand high standards of quality and reliability from producers based on ISO 9001 and IATF 16949. Also, the construction, agriculture and furniture industries are raising their expectations for deliveries from year to year.
Automotive companies issue their standards specifying specific requirements for products. One of these standards is the aviation standard SAE USCAR 8-4; 2019, which speaks of a compatible arrangement of fibers in the bolt head and in the area of transition into the mandrel.
The article presents the cold forging process of flange bolts. Obtaining a compatible, acceptable and incompatible grain flow pattern based of the above mantioned standard was presented. Then the results of FEM simulation were correlated with the performed experiment.
The effect of incompatible grain flow system was discussed and presented as the crack initiating factor due to delta ferrite, hydrogen embrittlement, tempering embrittlement. The reliability of the connections was confirmed in the assembly test for yield stress on a Schatz machine. The advantages of this method and the difference compared to the tensile test were presented.
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Bibliography

[1] IA TF 16949: 2016 – Automotive Quality Management System Standard.
[2] ISO 9001: 2015 – Systemy zarządzania jakością – Wymagania.
[3] A. Komornicka, M. Sąsiadek, T. Nahirny, Wyzwania przemysłu motoryzacyjnego w świetle wprowadzania standardów IATF 16949:2016, [in:] R. Knosali, Innowacje w Zarządzaniu i Inżynierii Produkcji, Oficyna Wydawnicza Polskiego Towarzystwa Zarządzania Produkcją.
[4] S. Ziółkiewicz, S. Stachowiak, D. Kaczmarczyk, A. Karpiuk, Obróbka Plastyczna Metali 17 (1), 7-13 (2006).
[5] A. Żmudzki, P. Skubisz, J. Sińczak, M. Pietrzyk, Obróbka Plastyczna Metali 17 (3), 9-19 (2006).
[6] N . Biba, S. Stebounov, A. Lishiny, J. Mater. Process. Tech. 113, 34-39 (2001).
[7] M Saad, S. Akhtar, M. Srivastava, J. Chaurasia, Materials Today: Proceedings 5, 19576-19585 (2018).
[8] A . Dubois, L. Lazzarotto, L. Dubar., J. Oudin, Wear 249, 951-961 (2002).
[9] Y . Nugraha, Theory of WireDrawing, Tirtayasa University (2007).
[10] S.Y. Hsia, Y.T. Chou, J.C. Chao, Advances in Mechanical Engineering 8 (3), 1-10 (2016).
[11] R . Bussoloti, L. Albano, L. de Canale, G.E. Totten, Delta Ferrite: Cracking of Steel Fasteners, [in:] R. Colás, G.E. Totten, Encyclopedia of Iron, Steel, and Their Alloys, Five-Volume Set, CRC Press (2006).
[12] D .H. Herring, Indust Heat 73 (16), 9 (2006).
[13] S.V. Brahimi, S. Yue, K.R. Sriraman, Philos. Trans. A Math. Phys. Eng. Sci. 375 (2098), (2017).
[14] SAE USCAR 8-4;2019 „Grain Flow Pattern for Bolts, Screws and Studs”.
[15] PN -EN 26157-3. Części złączne – Nieciągłości powierzchni – Śruby, wkręty i śruby dwustronne specjalnego stosowania.
[16] ISO 898-1:2013-06 Własności mechaniczne części złącznych wykonanych ze stali węglowej oraz stopowej – Część 1: Śruby i śruby dwustronne o określonych klasach własności – Gwint zwykły i drobnozwojny.
[17] ISO 16047:2007 Części złączne – Badanie zależności moment obrotowy/siła zacisku.
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Authors and Affiliations

T. Dubiel
1
ORCID: ORCID
T. Balawender
2
ORCID: ORCID
M. Osetek
1
ORCID: ORCID

  1. Koelner Rawlplug IP Sp. z o. o. Oddział w Łańcucie / Rzeszów University of Technology, Poland
  2. Rzeszów University of Technology, 12 Powstańców Warszawy Av., 35-959 Rzeszów, Poland
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Abstract

The article presents an analysis of stresses in the current tool system of the die during the implementation of the third forging operation of the screw M12 class 10.9 with cylinder head and hexagonal socket. It was assumed that the level of negative cracking due to stress can be reduced by using a mounting interference between the die and the tube blank. Due to the design of the tool system value of the die, the interference value cannot be too large. Therefore, an analysis of the influence of the interference between the die and the tube blank in a die tool system on the value and distribution of stresses in the individual components. An analysis of the assembly stresses and the stresses occurring during the process of deformation of the shaped head of the screw was done. The calculations were performed using a commercial software package MARC / Mentat.

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Authors and Affiliations

I. Nowotyńska
S. Kut
M. Osetek
ORCID: ORCID
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Abstract

The problem of setting out in civil engineering applications has been addressed in the literature for a long time. However, technological development has provided researchers with an opportunity of having other procedures in line with modern techniques in surveying sciences. One of the most important procedures in erecting steel structures, bridges, and precast columns of a building is the accurate placement of the anchorage system in concrete. The traditional method for staking out anchor bolts relies on sight rails, string lines, and tape measure. The precision of this art depends not only on the accuracy of observed offset distances during layout operations but also on the centerline of the anchoring template itself. Nowadays, the process of designing structures is executed using software that can perform a digital plan in CAD environment, where the coordinates of each anchor bolt can be defined. This research presents an accurate approach of positioning anchor bolts based on the second problem in surveying and total station. Error analysis and field application are described to evaluate the performance of the proposed method. However, the results indicate that the developed technique increases productivity, reduces the cost, and improves the positional accuracy.

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Authors and Affiliations

M. Habib
A. Malkawi
M. Awwad
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Abstract

The efficient protection (support reinforcement) of a wall and heading crossing ensures continuity of the production cycle, and that is a quick moving of the scraper conveyor to the wall. Using low or high bolting as a support reinforcement element in wall and heading crossings allows for the elimination of traditional methods of maintaining longwall-gate crossings, and therefore allows for the efficient use high performance modern wall complexes. The paper presents the long underground experience, of the Knurów–Szczygłowice mine of efficient support wall and heading crossing maintenance, which was bolted to the rock mass with the usage of two pairs of bolts, showing full technical and economical usefulness of this support reinforcement method. The article also highlights work safety and the increasingly common usage of endoscopies when specifying the range of crack areas which directly effects the proper choice in number, load-capacity and length of the used bolts. The underground studies the measurements of the reach of the zones of fracturing and roof stratification (using endoscopes and wire type stratification meters) and the laboratory tests (using the test stand) have allowed to determine the safety factor for maintenance of the longwall gangway crossing, directly resulting in the necessity to install additional reinforcement. The value of the safety factor Sbsc-ch greater than 1 is advantageous and safe, and the value less than or equal to 1 can lead to a significant deterioration of the conditions of maintenance of a wall and heading crossing which was bolted.

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Authors and Affiliations

Stanisław Duży
Piotr Głuch
Grzegorz Michalik
Adam Ratajczak
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Abstract

The paper presents the statical research tests of rod bolt made of plastic with a length of 5.5 m, which were performed in a modern laboratory test facility at the Department of Underground Mining of the University of Science and Technology. Innovative The Self-excited Acoustic System (SAS) used to measure stress changes in the bolt support was characterized. The system can be used for the non-destructive evaluation of the strain of the bolt around the excavations as well as in tunnels. The aim of the study was to compare the re-sults recorded by two different measuring systems, thanks to which it will be possible to assess the load of long bolt support by means of the non-destructive method. The speed and simplicity of measurement, access to the sensors, accuracy of measurement and reading should be kept in mind in determining the load of rock bolt support . In addition, the possibility of damage to the sensor as a re-sult of technological or natural hazards should also be taken into account. In economic conditions, the „technical - balance laws of production”, which ex-cludes the use of load sensors on each bolt must be preserved. The use of indi-vidual load sensors of rock bolt support for the boundary state, allows appro-priate protection actions of the mining crew against sudden loss of excavation stability to be taken. The paper presents two basic effects used in the ultrasonic measurement sys-tem. The first result was the existence of stable limit cycle oscillations for posi-tive feedback. This effect is called the self-excited effect. The second effect is called the elasto-acoustic effect. It means that with the change of elastic stress-es in the material bring the change of the speed of propagation of the wave. In this connection, the propagation time between measuring heads is also changed. This effect manifests itself in the change in the oscillation frequency of the self-excited system. For this reason, by measuring the frequency of self-excited oscillation, it is possible to indirectly determine the level of effort of the tested material.

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Authors and Affiliations

Krzysztof Skrzypkowski
Waldemar Korzeniowski
Krzysztof Zagórski
Krzysztof Lalik
Ireneusz Dominik
Janusz Kwaśniewski
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Abstract

In this work, the support of two general galleries located in poor quality rock mass and subjected to the influence of high thickness coal layer exploitations is designed and optimized. The process is carried out in four phases:

A first preliminary support is defined employing different geomechanical classifications and applying the New Austrian Tunnelling Method (NATM) using bolts and shotcrete.

An instrumentation campaign is carried out with the goal of analysing the behaviour of the support. The study noticed the failure of the support due to the time of placement of the different elements.

A back-analysis using the Flac and Phases software has allowed the evaluation of the properties of the rock mass and the support, the study of the influence of the time of placement on the component elements (bolts and shotcrete), and the redefinition of that support.

Subsequently, a new support is designed and optimized through numerical modeling after the start of mining without experience in these sizes of sublevel caving that caused the failure of the previously designed support. The new support is formed by yieldable steel arches that are more suitable to withstand the stresses generated by nearby mining work.

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Authors and Affiliations

Daniel Vázquez-Silva
Maria-Belen Prendes-Gero
Martina-Inmaculada Álvarez-Fernández
Celestino González-Nicieza
Carlos Laín-Huerta
Fernando López-Gayarre
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Abstract

Based on the electromechanical equivalent circuit theory, equations related to the resonance frequency and the magnifying coefficient of a quarter-wave vibrator and a quarter-wave taper transition horn were deduced, respectively. A series of 3D models of ultrasonic composite transducers with various conical section length was also established. To reveal the influences of the conical section length and the prestressed bolt on the dynamic characteristics (resonance frequency, amplitude, displacement node, and the maximum equivalent stress) of the models and the design accuracy, finite element (FE) analyses were carried out. The results show that the addition of prestressed bolt increases the resonance frequency and causes the displacement node on the center axis to move towards the small cylindrical section. As the conical section length rises, the increment of resonance frequency reduces and tends to a stable value of 360 Hz while the displacement of the node on the center axis becomes lager and gradually approaches 1.5 mm. Furthermore, the amplitude of the output terminal is stable at 16.18 μm under 220 V peak-topeak (77.8 VRMS) sinusoidal potential excitation. After that, a prototype was fabricated and validated experiments were conducted. The experimental results are consistent with that of theory and simulations. It provides theoretical basis for the design and optimization of small-size, large-amplitude, and high-power composite transducers.

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Authors and Affiliations

Tao Chen
Hongbo Lil
Qihan Wang
Junpeng Ye
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Abstract

In Eurocode 5, the stiffness equation for bolted steel-wood-steel is stated as a function ofwood density and fastener diameter only. In this research, an experimental study on various configurations of tested bolted steel-wood-steel (SWS) connections has been undertaken to predict the initial stiffness of each connection. In order to validate the Eurocode 5 stiffness equation, tests on 50 timber specimens (40 glued laminated timbers and 10 laminated veneer lumbers (LVL)) with steel plates were undertaken. The number of bolts was kept similar and the connector diameter, timber thickness, and wood density were varied. The results obtained in the experimental tests are compared with those obtained from the Eurocode 5 stiffness equation. From the analysis, it is signified that the stiffness equation specified in Eurocode 5 for bolted SWS connections does not adequately predict the initial stiffness. The results from Eurocode 5 stiffness equation are very far from the experimental values. The ratio of stiffness equation to experimental results ranges from 3.48 to 4.20, with the average at 3.77, where the equation overpredicted the experimental stiffness value for the connection. There is a need to consider or incorporated other parameters such as geometric configurations in Eurocode 5 stiffness equation to improve the ratio with the experimental data.
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Authors and Affiliations

Nur Liza Rahim
1 2
ORCID: ORCID
Gary Raftery
3
ORCID: ORCID
Pierre Quenneville
3
ORCID: ORCID
Doh Shu Ing
4
ORCID: ORCID
Marcin Nabiałek
5
ORCID: ORCID
Ramadhansyah Putra Jaya
4 6
ORCID: ORCID
Norlia Mohamad Ibrahim
1 7
ORCID: ORCID
Mohd Mustafa Al Bakri Abdullah
8 6
ORCID: ORCID
Agata Śliwa
9
ORCID: ORCID

  1. University Malaysia Perlis, Faculty of Civil Engineering Technology, 02600 Arau Perlis, Malaysia
  2. 2Sustainable Environment Research Group (SERG), Centre of Excellence Geopolymer and Green Technology (CEGeoGTech), University Malaysia Perlis (UniMAP), 01000 Kangar Perlis, Malaysia
  3. University of Auckland, Faculty of Civil Engineering, Department of Civil and Environmental Engineering, Auckland, New Zealand
  4. Department of Civil Engineering, College of Engineering, University Malaysia Pahang, 26300 Gambang Kuantan, Pahang Malaysia
  5. Czestochowa University of Technology, Czestochowa, Poland
  6. Centre of Excellence Geopolymer and Green Technology (CEGeoGTech), University Malaysia Perlis (UniMAP), 01000 Kangar Perlis, Malaysia
  7. Sustainable Environment Research Group (SERG), Centre of Excellence Geopolymer and Green Technology (CEGeoGTech), University Malaysia Perlis (UniMAP), 01000 Kangar Perlis, Malaysia
  8. University Malaysia Perlis, Faculty of Chemical Engineering Technology, 02600 Arau Perlis, Malaysia
  9. Division of Materials Processing Technology and Computer Techniques in Materials Science, Silesian University of Technology, 44-100 Gliwice, Poland
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Abstract

The paper is devoted to a bolted flanged joint with a flat ring gasket. Simple mathematical models of the flat ring gasket and the flange are formulated. Solutions to the models allowed determining numerically effective shapes of the flat ring and the flange. In the case of the gasket a minimal tension of the bolts was assumed as a criterion, while in the case of the flange the criterion of minimal angle of the flange rotation was applied. Results of the study, shown in the Figures, may serve for practical purposes in designing of pressure vessels and piping.
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Authors and Affiliations

Krzysztof Magnucki
ORCID: ORCID
Zygmunt Sekulski
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Abstract

The article aims at assessing the influence of the drill bit material on the bearing strength of holes made in glass fabric reinforced epoxy composite. Six twists made of widely used drill materials such as high speed steels and carbides in different configurations were selected to drill holes in the composite. In the first stage of the work, optimum drilling parameters were selected and then used for drilling holes in specimens tested in single lap shear experiments. For each tested specimen two different delamination factors, one based on the delamination area and another - on its diameter, were calculated in order to assess the quality of the holes and then compared to the results of the bearing strength experiments. The results of the bearing tests showed that the highest strength was achieved for the high speed steel drill with titanium coating while the lowest for the cemented carbide drill. This finding is in opposition to the majority of results reported in literature.
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Authors and Affiliations

Anna Galińska
1
ORCID: ORCID

  1. Warsaw University of Technology, Faculty of Power and Aeronautical Engineering, Warsaw, Poland
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Abstract

Large deformation in roadways is an inevitable problem faced by many coal mines, and bolt installation is widely adopted to keep roadway stability. To provide a theoretical basis for bolt supporting scheme design in order to eliminate hazards associated with roadway failure, the interaction principle between bolts and the bolted strata should be studied thoroughly. This research attempts to investigate the above principle through theoretical analysis through a group of selected statistics from fifteen different coal mines. At the same time, the thick board support method was proposed and applied for controlling the ribs deformation in a particular coal mine. It is concluded that the interaction of the rock-bolt entity is subjected to the fluctuation balance law. When deformation increases, the bolted structure experiences periodic equilibrium variation. Both the supporting force needed to stabilise the surrounding rocks and the supporting capability of bolted strata show a trend of decrease in this process. The interaction principle of surrounding rocks and bolts is in essence the mechanical phenomenon caused by their mutual load transformation, and the load-carrying capacity varies with the bolted structure’s deformation, which is subjected to the following law: elastic roadway>plastic roadway> fractured roadway>broken roadway. The designed bolted thickness of the ribs should be more than 1/5 of roadway height to make full use of the self-stability of surrounding rocks. Finite Difference Method simulation and on-site monitoring data showed that the roof subsidence and ribs convergence of 2201 roadway in Shuguang coal mine was reduced by 83.7% and 88.6% respectively after utilising the proposed support method, indicating that the thick-board method was effective. Results of this research can lay a foundation for support design in large deformation roadways.
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Authors and Affiliations

Xun Yuan
1
ORCID: ORCID
Shuangsuo Yang
2
ORCID: ORCID

  1. Sichuan University – The Hong Kong Polytechnic University, Institute for Disaster Managementand Reconstruction, 610207 Chengdu, China
  2. Taiyuan University of Technology, College of Mining Engineering, 030024 Taiyuan, China
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Abstract

Monitoring the stress change of bolt and knowing the anchoring condition in a reasonable and effective way, accurately, can effectively prevent tunnel accident from breaking out. The stress of rock mass around the roadway is usually transferred to the anchor rod in the form of axial load, so it is of great significance to study the axial load of the bolt. In this paper, a full size anchoring and drawing experiment system was designed and established, innovatively, which realized the pull-out test of 2.5 m prestressed end Anchorage and the full-length Anchorage by using the new resin anchorage agent under vertical and horizontal loads. Through the application of fiber Bragg grating (FBG) sensing technology to the test of full-scale anchor rod, the axial force distribution characteristics of the end Anchorage and the full-length Anchorage anchor rod were obtained under the action of pre-tightening torque and confining rock pressure. The comparison indicates that the proportion of high stress range accounts for only 17.5% and the main bearing range is near the thread end of anchor rod, the proportion of main bearing range of end Anchorage is 83.3%, and the feasibility of FBG force-measuring anchor rod is verified in the field. The research results have certain reference value.

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Authors and Affiliations

Tuo Wang
Jucai Chang
Peng Gong
ORCID: ORCID
Wenbao Shi
Ning Li
Shixing Cheng
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Abstract

The cohesion and internal friction angle were characterized as quadratic functions of strain and were assumed to follow the Mohr-Coulomb criterion after the yield of peak strength. These mechanical parameters and their variations in post-peak softening stage can be exactly ascertained through the simultaneous solution based on the data points of stress-strain curves of triaxial compression tests. Taking the influence of the fault into account, the variation of strata pressure and roadway convergence with coal advancement, the temporal and spatial distribution of axial bolt load were numerically simulated by FLAC3D (Fast Lagrangian Analysis of Continua) using the ascertained post-peak mechanical parameters according to the cohesion weakening and friction strengthening model. The change mechanism of axial load of single rock bolt as abutment pressure changes was analyzed, through the comparison analysis with the results of axial bolt load by field measurements at a coal mine face. The research results show that the simulated results such as the period of main roof weighting, temporal and spatial distribution of axial bolt load are in accordance with field measurement results, so the validity of the numerical model is testified. In front of the working face, the front abutment pressure increases first and then decreases, finally tends to be stable. A corresponding correlation exists between the variation of axial bolt load and rock deformation along the bolt body. When encountered by a fault, the maximum abutment pressure, the influential range of mining disturbance and the roadway convergence between roof and floor before the working face are all increased. In the roadways along the gob, axial bolt loads on the side of the working face decrease, while the other side one increases after the collapse of the roof. As superficial surrounding rock mass is damaged, the anchoring force of rock bolts will transfer to inner rock mass for balancing the tensile load of the bolts.

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Authors and Affiliations

Hao Shi
Houquan Zhang
Lei Song
ORCID: ORCID
Yu Wu
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Abstract

The conduction of mining activity under the conditions of rock bursts and rock mass tremors means that designers often utilise support systems comprising various configurations of steel arch, rock bolt and surface support. Particularly difficult geological and mining conditions, when wire mesh does not provide sufficient dynamic resistance, it requires an additional reinforcement with wire rope lacing in the form of steel ropes installed between the bolt ends and fixed to them by means of various rope clamps (e.g. u-bolt clamps). Bench tests were conducted to compare the strength of wire ropes under static and dynamic loading. The tests involved wire ropes with an internal diameter of Ø15.7 mm. Tests under static loading demonstrated that the cable bolts transferred a maximum force Fs max = 289.0 kN without failure, while the energy absorbed until failure was E 1s = 16.6 kJ. A comparative test result analysis for the wire ropes used in the bolt designs revealed that the influence of dynamic loading forces has a significant effect on reducing the rope load capacity, which results in the brittle cracking of the wires in the rope. Although the average dynamic force leading to wire rope failure F dmax = 279.1 kN is comparable to the minimum static force Fmin = 279 kN defined in the relevant standard, the average energy E1d absorbed by the cable bolt until failure is 48% lower than the energy E1s determined for wire rope failure under static loading. Furthermore, cable bolt failure under dynamic loading occurred at an impact velocity of the combined ram and crosshead masses ranging within vp = 1.4-1.5 m/s.
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Authors and Affiliations

Andrzej Pytlik
1
Mariusz Szot
1
ORCID: ORCID

  1. GIG – National Research Institute, Plac Gwarków 1, 40-166 Katowice, Poland
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Abstract

Numerical analysis of robustness assessment of steel planar framed structures under sudden external column removal is presented. The analysis is based on the previous experimental and numerical analyzes conducted in the Ph.D. project.Advanced and validated finite element models of steel structures with bolted end plate joints were used using Abaqus software. Six different cases of analysis using flush and extended bolted end-plate joints were performed. The actual results of the axial forces and rotations of the joints, failure models, and other important factors about structure behaviour are presented. The clear division of the results obtained depended on the type of joint used in the structure. In the cases of application of extended end-plate joints in frame analysis, the required level of robustness was reached in all cases and stopping of collapse development was obtained. In all cases of frame analysis with flush end-plate joints, an insufficient level of robustness on progressive collapse was obtained and partial failures of the structures were reached. Due to the location of the external column, the catenary actions to mitigate progressive collapse were very limited.
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Authors and Affiliations

Aleksander Kozlowski
1
ORCID: ORCID
Damian Kukla
1
ORCID: ORCID

  1. Rzeszów University of Technology, Faculty of Civil and Environmental Engineering and Architecture, Poznanska 2, 35-084 Rzeszów
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Abstract

Looseness of high-strength wind turbine bolts is one of the main types of mechanical failure that threaten the quality and safety of wind turbines, and how to non-destructively detect bolt loosening is essential to accurate assessment of operational reliability of wind turbine structures. Therefore, to address the issue of looseness detection of high-strength wind turbine bolts, this paper proposes a non-destructive detection method based on digital image correlation (DIC). Firstly, the mathematical relationships between the inplane displacement component of the bolt’s nut surface, the bolt’s preload force loss and the bolt loosening angle are both deduced theoretically. Then, experimental measurements are respectively conducted with DIC with different small bolt loosening angles. The results show that the bolt loosening angle detection method based on DIC has a detection accuracy of over 95%, and the bolt’s preload force loss evaluated by the deduced relationship has a good agreement with the empirical value. Therefore, the proposed DIC-based bolt loosening angle detection method can meet the requirements of engineering inspection, and can achieve quantitative assessment of preload forces loss of wind turbine bolt.
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Authors and Affiliations

Wei-Guo Xie
1
Peng Zhou
1
Li-Yun Chen
1
Guo-Qing Gu
2
Yong-Qing Wang
3
Yu-Tao Chen
4

  1. Yancheng Institute of Supervision & Inspection on Product Quality, Yancheng 224056, China
  2. School of Civil Engineering, Yancheng Institute of Technology, Yancheng 224051, China
  3. School of Electrical Engineering, Yancheng Institute of Technology, Yancheng 224051, China
  4. School of Mechanical Engineering, Yancheng Institute of Technology, Yancheng 224051, China
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Abstract

Block tearing is a failure mode of steel connections based on rupture of material. In this paper, a numerical model is developed to capture fracture initiation and progression until failure in steel angles connected by one leg using single row of bolts. It was realized using Gurson-Tvergaard-Needleman porous material model, which can accurately trace the behaviour of steel at plastic and ultimate range. Obtained results are validated on laboratory test results in global and local terms. Stress distribution along the failure paths in the gross and net area subjected to shear and tension was investigated for different geometrical arrangements of connections. Observation of rupture mechanisms allowed to compare the design procedures given in Eurocode 3 with connections behaviour. Results of analysis indicate that both plastic stress distribution in gross shear area and ultimate stress distribution in net shear area can limit block tearing resistance, which is consistent with the newest code provisions.
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Authors and Affiliations

Edyta Bernatowska
1
ORCID: ORCID
Lucjan Ślęczka
1
ORCID: ORCID

  1. Rzeszow University of Technology, Faculty of Civil and Environmental Engineering and Architecture, Poznanska 2 Street, 35-084 Rzeszow,
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Abstract

Full-length bonded bolts are widely used in deep mining engineering and an in-depth understanding of their mechanical characteristics under complex and high ground stress conditions is of great significance for deep roadway support systems. Based on a quantitative GSI rating system of surrounding rocks and rock nonlinear dilatancy angle model, a nonlinear dilatancy angle model suitable for jointed rocks was developed. The Hoek–Brown strain-softening model parameters were transformed into equivalent Mohr–Coulomb strength parameters, and a numerical model of the deep roadway was constructed using FLAC 3�� numerical simulation software as a tool. The force characteristics of fulllength bonded anchors under different constitutive model and dilatancy angle model conditions were analyzed, and the effects of different lengths of anchors on the stability of the surrounding rock were studied. The obtained results revealed a big difference between the axial forces of bolts calculated by strain-softening and ideal elastic-plastic models. It was also found that bolt shear force was less influenced by the strain-softening behaviors of surrounding rocks. Dilatancy angle greatly affected bolt axial force. Therefore, if the dilatancy angle was neglected, great errors would be created in the calculation results of supporting structure designs. The nonlinear dilatancy angle model of jointed rock masses more accurately captured the stress properties of bolts after field monitoring and analysis. The findings of the study can serve as a guide for calculating the stability of surrounding rocks in deep mining engineering.
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Authors and Affiliations

Zenghua Lin
1
ORCID: ORCID

  1. School of Civil Engineering, University of Science and Technology Liaoning, China
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Abstract

The current design codes recommend designing the building structures based on the assumption avoiding the disproportionate to the initial cause damage during accidental situation. As a main strategy to mitigate a progressive collapse an alternative load path method is recommended. Flush and extended bolted end-plate joint to connect beam-to-column were experimentally tested. Hierarchical validation of joint FEM models based on experimental test results were performed. The numerical dynamic analysis by finite element method of selected steel frame under column loss scenario is presented. The planar 2D model of frame were used. Shell elements for beams and columns and solid elements for joints were employed respectively. Nonlinear material and geometry were applied in the analysis. Johnson-Cook model was used to describe the change of steel parameters by dynamic Increase Factor (DIF). The Rayleigh model to include the damping effects in the analysis was used. The dynamic analysis was performed with the use of Abaqus/Explicit module. Main conclusion of presented research it that to achieve the required level of robustness, bolted beam-to-column joints with extended end-plate of thickness more than 15 mm should be used.
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Authors and Affiliations

Damian Kukla
1
ORCID: ORCID
Aleksander Kozlowski
1
ORCID: ORCID

  1. Rzeszów University of Technology, Faculty of Civil and Environmental Engineering and Architecture, Poznanska 2, 35-084 Rzeszów, Poland
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Abstract

In civil engineering structures, steel angles are often used as tensioned elements, because of their ease of fabrication and assembly. For practical reasons, angles are usually connected only by one leg, using a single row of bolts, and rupture of weakened section usually determines a joint capacity. Also, eccentricity affects the distribution of stresses in the net section and hence its load capacity. Assessment of ultimate resistance is a completely different issue compared to the well-known and established problems of plastic resistance and requires advanced material modelling. The paper presents a numerical simulation of net section failure of tensioned angles, made of structural steel grade S275, taking into account ductile initiation and propagation of fracture using the Gurson–Tvergaard– Needleman damage model. Extensive parametrical analysis of ultimate tensile resistance was performed with a wide range of parameters. The typical and well-recognised failure modes were observed as net section fracture and block tearing. Also, an additional failure mode, classified as limited block tearing, has occurred which is not considered in current design provisions. The paper describes the impact of individual geometrical properties of the joint (numbers of bolts, connection length, and distance from the edge of the connected leg to the center of the fastener hole) on the apparent failure form and the resistance obtained.
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Authors and Affiliations

Edyta Bernatowska
1
ORCID: ORCID
Lucjan Ślęczka
1
ORCID: ORCID

  1. Rzeszów University of Technology, Faculty of Civil and Environmental Engineering and Architecture, Poznanska 2, 35-084 Rzeszów, Poland
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Abstract

Joints in cold-formed steel framing structures are usually designed as bolted lap type ones with a gusset plate. Unlike the end-plate joints in hot-rolled structures, the load in such joints is transferred through shearing of the bolts and bearing of the material. The prediction of their structural properties may be problematic in viewof unfavourable influence of the hole clearance and hole ovalization resulting from low bearing resistance of thin walls. A few experimental programmes showed that these issues lead to a different behaviour of the whole joint comparing to common end plate type. These concerns may be particularly important for joints under variable loading, which are prone to deterioration of structural properties. The testing programme conducted by the authors was focused on their behaviour under monotonic and cyclic loading with attention to a potential drop of resistance and stiffness. Monotonic tests revealed quite similar course of the joints’ response. In view of high deformability of the specimens at the intermediate stage of each monotonic test, plastic moment resistances of joints were associated with the initial part of the moment-rotation curves and were multiple times lower than maximum moments obtained in the experiments. The quantities of deterioration of structural properties were determined based on cyclic tests. Drop of resistance and stiffness was observed for several levels of loading range, but the trend of decrease varied for each property. Application of the DIC technique allowed one to identify qualitatively and quantitatively the sources of joint deformability.
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Authors and Affiliations

Rafał Budzinski
1
ORCID: ORCID
Lucjan Ślęczka
1
ORCID: ORCID

  1. RzeszowUniversity of Technology, Faculty of Civil and Environmental Engineering and Architecture, Al. Powstanców Warszawy 12, 35-959 Rzeszów, Poland

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