scholarly journals Adjustment of the Yielding System of Mechanical Rock Bolts for Room and Pillar Mining Method in Stratified Rock Mass

Energies ◽  
2020 ◽  
Vol 13 (8) ◽  
pp. 2082 ◽  
Author(s):  
Krzysztof Skrzypkowski ◽  
Waldemar Korzeniowski ◽  
Krzysztof Zagórski ◽  
Anna Zagórska
Keyword(s):  
Numerical Modeling ◽  
Impact Energy ◽  
Laboratory Tests ◽  
Ore Deposits ◽  
Rock Bolt ◽  
Rock Bolts ◽  
Damage Area ◽  
Rock Bolt Support ◽  
The Impact ◽  
Bolt Support

The article presents a novel yielding mechanism, especially designed for the rock bolt support. Mechanical rock bolts with an expansion head and equipped with one, two, four and six dome bearing plates were tested in the laboratory conditions. Furthermore, in the Phase2D numerical program, five room and pillar widths were modeled. The main aim of numerical modeling was to determine the maximal range of the rock damage area and the total displacements in the expanded room. The models were made for a room and pillar method with a roof sag for copper ore deposits in the Legnica-Głogów Copper District in Poland. Additionally, in the article a load model of the rock bolt support as a result of a geomechanical seismic event is presented. Based on the results of laboratory tests (load–displacement characteristics), the strain energy of the bolt support equipped with the yielding device in the form of dome bearing plates was determined and compared with the impact energy caused by predicted falling rock layers. Based on the laboratory tests, numerical modeling and mathematical dynamic model of rock bolt support, the dependence of the drop height and the corresponding impact energy for the expanded room was determined.

scholarly journals Case Studies of Rock Bolt Support Loads and Rock Mass Monitoring for the Room and Pillar Method in the Legnica-Głogów Copper District in Poland

Energies ◽  
2020 ◽  
Vol 13 (11) ◽  
pp. 2998 ◽  
Author(s):  
Krzysztof Skrzypkowski
Keyword(s):  
Underground Mining ◽  
Mechanical Load ◽  
Ground Surface ◽  
Rock Bolt ◽  
Copper Ore ◽  
Essential Condition ◽  
Rock Bolting ◽  
Rock Bolt Support ◽  
The Impact ◽  
Bolt Support

The article presents the impact of geological and mining factors on the stability of room excavations in the Legnica-Głogów Copper District (LGOM) in Poland. In underground mining, the primary task of bolting of mining excavations is to ensure their stability as an essential condition of work safety. Appreciating the role and importance of the rock bolting in Polish ore mining; rock bolt load sensors were designed, manufactured and tested under laboratory conditions. The purpose of the research was to characterize the sensors and determine the elastic range of the bearing plate, which are an integral part of the sensor. The sensors have been verified in industrial conditions. The tests were carried out in the underground copper ore mine in Poland. Three rooms in the exploitation field were selected for testing, where exploitation was carried out at a depth of 809–820 m below the ground surface with the application of room and pillar with roof deflection and maintaining the central part of the field. The exploitation field included 60 rooms and pillars. The effectiveness of the mechanical load sensor of the expansion rock bolt support has been experimentally confirmed. Based on mine research, it was found that the largest increases in the load of the rock bolting, vertical stress and convergence occur in the middle of the mining field.

scholarly journals Effect of Near-Wave Field Mining Tremors on the Rock Bolt Support Behaviour within Stress Domain

2019 ◽  
Vol 105 ◽  
pp. 01007
Author(s):  
Witold Pytel ◽  
Krzysztof Fuławka ◽  
Piotr Mertuszka
Keyword(s):  
Wave Field ◽  
Dynamic Effect ◽  
Stability Loss ◽  
Rock Bolt ◽  
Risk Level ◽  
Roof Fall ◽  
Rock Bolt Support ◽  
Stratum Deformation ◽  
The Impact ◽  
Bolt Support

One of the most serious hazard in the underground copper mining in Poland is the roof fall hazard. The scale and intensity of this type of events depends on several factors. Due to seismic activity, weaker roof strata can loosen and deform, generating additional load on the rock bolt support. The type of load depends strictly on the course of stratum deformation as well as on the intensity of the dynamic effect in the form of a seismic wave. Continuous monitoring is then necessary to determine the risk level of stability loss within existing excavations in order to minimize the probability of serious accidents. The following study analyses the impact of tremors recorded within the near-wave field upon the stress change in the instrumented rock bolts.

Laboratory Method for Evaluating the Characteristics of Expansion Rock Bolts Subjected to Axial Tension / Laboratoryjna Metoda Badania Charakterystyk Kotew Rozprężnych Poddanych Rozciąganiu Osiowemu

2015 ◽  
Vol 60 (1) ◽  
pp. 209-224 ◽  
Author(s):  
Waldemar Korzeniowski ◽  
Krzysztof Skrzypkowski ◽  
Łukasz Herezy
Keyword(s):  
Rock Mass ◽  
Laboratory Method ◽  
Operating Conditions ◽  
Rock Bolt ◽  
Test Facility ◽  
Geometrical Parameters ◽  
Rock Bolts ◽  
Axial Tension ◽  
Rock Bolt Support ◽  
Bolt Support

Abstract Rock bolts have long been used in Poland, above all in the ore mining. Worldwide experience (Australia, Chile, Canada, South Africa, Sweden, and USA) provides evidence of rock bolt supports being used for loads under both static and dynamic conditions. There are new construction designs dedicated to the more extreme operating conditions, particularly in mining but also in tunneling. Appreciating the role and significance of the rock bolt support and its use in Polish conditions amounting to millions of units per year, this article describes a new laboratory test facility which enables rock bolt testing under static load conditions. Measuring equipment used as well as the possibilities of the test facility were characterized. Tests were conducted on expansion rock bolt supports installed inside a block simulating rock mass with compression strength of 80 MPa, which was loaded statically as determined by taking account of the load in order to maintain the desired axial tension, which was statically burdened in accordance with determined program load taking into consideration the maintenance of set axial tension strength at specified time intervals until capacity was exceeded. As an experiment the stress-strain characteristics of the rock bolt support were removed showing detailed dependence between its geometrical parameters as well as actual rock bolt deformation and its percentage share in total displacement and deformation resulting from the deformation of the bolt support elements (washer, thread). Two characteristic exchange parts with varying intensity of deformation /displacement per unit were highlighted with an increase in axial force static rock bolt supports installed in the rock mass.

scholarly journals Modified Rock Bolt Support for Mining Method with Controlled Roof Bending

Energies ◽  
2020 ◽  
Vol 13 (8) ◽  
pp. 1868 ◽  
Author(s):  
Krzysztof Skrzypkowski ◽  
Waldemar Korzeniowski ◽  
Krzysztof Zagórski ◽  
Anna Zagórska
Keyword(s):  
Laboratory Tests ◽  
Deformation Energy ◽  
Rock Bolt ◽  
Raw Material ◽  
Mining Method ◽  
Underground Excavations ◽  
Bearing Plate ◽  
Additional Work ◽  
Rock Bolt Support ◽  
Bolt Support

The article presents methods of making the rock bolt support more yieldable, especially for a stratified roof. Alongside the increasing depth of exploitation of raw material deposits, rock bolt support units are more often designed taking into account more intensive deformations and displacements of underground excavations. In the article, a room and pillar method with mined roof bending and roof reinforcement with bolt patterns of 1 m × 1 m, 1.5 m × 1.5 m and 2 m × 2 m is presented. Moreover, the laboratory tests included 1.8 m long bolts, which were embedded segmentally on the lengths of 100 mm, 150 mm and 200 mm were tested. Based on the load–displacement characteristics, the deformation energy for flat and profiled dome bearing plates was calculated. Making the segmentally embedded resin rock bolt support yieldable enabled it to perform additional work. Furthermore, it was found that rock bolt support with a dome bearing plate took over 2.5 times more energy compared to a rock bolt support equipped with a flat bearing plate.

scholarly journals Evaluation of Rock Bolt Support for Polish Hard Rock Mines

2018 ◽  
Vol 35 ◽  
pp. 01006 ◽  
Author(s):  
Krzysztof Skrzypkowski
Keyword(s):  
Laboratory Tests ◽  
Underground Mining ◽  
Rock Bolt ◽  
Test Facility ◽  
Hard Coal ◽  
External Diameter ◽  
Copper Ore ◽  
Hard Coal Mining ◽  
Rock Bolt Support ◽  
Bolt Support

The article presents different types of rock bolt support used in Polish ore mining. Individual point resin and expansion rock bolt support were characterized. The roof classes for zinc and lead and copper ore mines were presented. Furthermore, in the article laboratory tests of point resin rock bolt support in a geometric scale of 1:1 with minimal fixing length of 0.6 m were made. Static testing of point resin rock bolt support were carried out on a laboratory test facility of Department of Underground Mining which simulate mine conditions for Polish ore and hard coal mining. Laboratory tests of point resin bolts were carried out, especially for the ZGH Bolesław, zinc and lead “Olkusz – Pomorzany” mine. The primary aim of the research was to check whether at the anchoring point length of 0.6 m by means of one and a half resin cartridge, the type bolt “Olkusz – 20A” is able to overcome the load.The second purpose of the study was to obtain load – displacement characteristic with determination of the elastic and plastic range of the bolt. For the best simulation of mine conditions the station steel cylinders with an external diameter of 0.1 m and a length of 0.6 m with a core of rock from the roof of the underground excavations were used.

Compressive Strength of CCF300/QY8911 Composite Laminates with LVI Damage

2012 ◽  
Vol 583 ◽  
pp. 203-206
Author(s):  
Hai Ming Hong ◽  
Ming Li ◽  
Jian Yu Zhang ◽  
Yi Ning Zhang
Keyword(s):  
Compressive Strength ◽  
Impact Energy ◽  
Composite Laminates ◽  
Inflection Point ◽  
Low Velocity Impact ◽  
Low Velocity ◽  
Damage Area ◽  
Compressive Performance ◽  
The Impact ◽  
Dent Depth

A series of low-velocity impact tests and residual compressive strength tests after impacts on CCF300/QY8911 composite materials were carried out to study the mechanism of compression failure of the laminates after low-velocity impact. The curves of impact energy verse dent depth and impact energy verse the damage area was obtained. And the residual compressive strength and stiffness after impact verse damage parameters were analyzed. The results showed that when the impact energy exceeded the inflection point, as the impact energy increased, the dent depth on the impacted surface of the laminates notably increased while the damage area of the internal layers merely increased slowly. If the impact energy was continued to increase, the expansion of the laminates' internal damage mainly consisted of fiber breaks. The main reason for the decrease in compressive performance of composite laminates was inside delamination between layers, while in the case in which impact energy exceeded the inflection point, there were no obvious changes in delamination damage area for different energy, so the residual compressive performance kept almost stable.

Study on Rock Bolt Support of Roadway of Coal Mine Using Neural Network

2013 ◽  
Vol 448-453 ◽  
pp. 3799-3802
Author(s):  
Feng Shan Han ◽  
Xin Li Wu
Keyword(s):  
Neural Network ◽  
Artificial Neural Network ◽  
Coal Mine ◽  
Engineering Application ◽  
Rock Bolt ◽  
Learning System ◽  
Artificial Neural ◽  
Complex Relationships ◽  
Rock Bolt Support ◽  
Bolt Support

The artificial neural network has been widely used in various field of science and engineering. The artificial neural network has marvelous ability to gain knowledge. In this paper, according to principle of artificial neural network , Model of artificial neural network of rock bolt support of roadway of coal mine has been constructed,Learning system of BP artificial neural network has been trained,it is shown by engineering application that artificial neural network can handle imperfect or incomplete data and it can capture nonlinear and complex relationships among variables of a system. the artificial neural network is emerging as a powerful tool for modeling with the complex system. Method and parameters of rock bolt support of roadway of coal mine can be predicated accurately using artificial neural network, that is of significance and valuable to those subjects of investigation and design of mining engineering

Impacted of Vacuum Bag Woven Kenaf/Fiberglass Hybrid Composite

2014 ◽  
Vol 660 ◽  
pp. 572-577
Author(s):  
Syarifah Yunus ◽  
Z. Salleh ◽  
M.A. Aznan ◽  
M.N. Berhan ◽  
A. Kalam ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Impact Energy ◽  
Hybrid Composite ◽  
Hybrid Composites ◽  
Advanced Technology ◽  
Damage Area ◽  
Bending Stresses ◽  
Post Impact ◽  
The Impact ◽  
Woven Kenaf

This paper discusses the mechanical properties of woven kenaf/fiberglass hybrid composites which has been fabricating using vacuum bag technique. Kenaf fiber had chosen among others natural fibres due to its excellent mechanical properties and potential natural raw fiber to replace plastic or tobacco in manufacturing a multitude of products for the construction, automotive, textile and advanced technology sectors. This study investigates post impact tensile of kenaf hybrid composites and its surface fractured. The impact energy used consists of 4J, 6J, 8J, 12J and 16J. The specimens were clamped between two plate rings with an internal hole diameter of 18mm and impacted with hemispherical nose impactor shape with diameter size of 12.7mm. The results revealed that this kenaf hybrid composite showed significant decreasing of strength and modulus as increasing the impact energy. The damage area affected with fiber fracture occurred much later in fracture process due to high bending stresses.

Improvement of Design and Installation of Injection Rock Bolt Support

2017 ◽  
Vol 53 (3) ◽  
pp. 513-518 ◽  
Author(s):  
R. A. Ignat’ev ◽  
E. R. Ignat’ev
Keyword(s):  
Rock Bolt ◽  
Rock Bolt Support ◽  
Bolt Support
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