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1
Content available The Effect of Undercut Anchor Diameter on the Rock Failure Cone Area in Pullout Tests
Jonak Józef, Karpiński Robert, Wójcik Andrzej, Siegmund Michał
Advances in Science and Technology. Research Journal
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2022
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Vol. 16, no 5
261–270
EN
The numerical analysis was conducted using the FEM ABAQUS software to establish the impact of various undercut anchor diameters on the rock breakout cone formation. The central focus of the investigations was on the rock breakout prism, which tends to be approximated to a cone or a quadrilateral pyramid, including its characteristic parameter, the angle of failure cone . Assuming that the embedment depth and the undercut anchor head angle were constant for the considered range of anchor head diameters, it remains unclear, however, precisely how the anchor head diameter affects the value of the failure cone angle, and thus the surface area of the full breakout prism. This conclusion stands in confirmation of our former considerations regarding the impact of the anchor head angle on the size of the breakout surface. Furthermore, it is supported by the results obtained from the mechanical model simulation of the anchor-rock system, where the anchor head angle and the effective embedment depth were determined as significant factors affecting the assumed rock breakout failure. The underlying aspect of the reported investigation was to evaluate the effectiveness of the non-conventional rock breakout technology performed with an undercut anchor, whose primary factors were both the pullout force and the assumed volume of the rock cone.
2
Content available Dynamics of autonomous rock electromagnetic radiation measurement instrumentation
Mydlikowski Remigiusz, Maniak Krzysztof
Bulletin of the Polish Academy of Sciences. Technical Sciences
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2021
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Vol. 69, nr 5
art. no. e138567
EN
The paper analyzes the operation of innovative composite measurement instrumentation for spontaneous electromagnetic emission. The designed receiver measures and records both components of the EM field emitted by rocks subjected to increased mechanical stress. The range of signals transmitted by the receiver system and its dynamics were determined. A receiver was used to observe electromagnetic signals generated during a hard coal sample crushing in laboratory conditions. Test results confirmed the high dynamic range of the system at 98 dB and the ability to observe signals over a range of frequencies up to 50 kHz. The experimental results confirm the signal bandwidth characteristic of coal mine EM field emission obtained in earlier studies. The constructed autonomous receiver can be used in mine workings as a complementary warning system for emerging mine hazards.
3
Content available Experimental Verification of Standard Recommendations for Estimating the Load-carrying Capacity of Undercut Anchors in Rock Material
Jonak Józef, Karpiński Robert, Siegmund Michał, Machrowska Anna, Prostański Dariusz
Advances in Science and Technology. Research Journal
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2021
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Vol. 15, no 1
230--244
EN
The recommendations put forward in the International Standards for anchorage in concrete concerning the assessment of the load-carrying capacity of anchors (the pull-out force) embedded in natural rock material were verified. Regarding the predicted extent of surface failure we have shown, in earlier studies, substantial discrepancies between the strength test results for anchorages in the rock mass and the established standard recommendations for anchorages in concrete. As regards the industrial practice and the goals of the reported project, simplified calculation procedures that will facilitate the selection of optimal configurations for the layout of anchor holes, while being computationally effective and applicable under the industry-specific conditions are sought.
4
Content available Autonomous Instrumentation for Measuring Spontaneous Electromagnetic Emissions in Mining
Maniak Krzysztof, Mydlikowski Remigiusz
Journal of Telecommunications and Information Technology
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2020
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nr 4
98--103
EN
This article presents the design of an innovative receiver capable of identifying electric and magnetic components of electromagnetic fields. The receiver senses and records electromagnetic disturbances generated as mine tunnels collapse. It offers excellent operating specification and the ability to sense and log magnetic and electrical component strength values in real time. The paper analyzes the data obtained with the use of a system installed in a working mine and attempts to determine hazards resulting from increased rock stress levels that, cause spontaneous EM emissions.
5
Content available Measurement of Electromagnetic Field Component Emissions as a Precursor of Emerging Hazard in Coal Mines
Mydlikowski Remigiusz, Maniak Krzysztof
Journal of Telecommunications and Information Technology
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2019
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nr 4
30--35
EN
The article presents the results of research concerning electromagnetic (EM) field emitted by rocks during the process of their destruction. The paper describes a measuring stand designed for subjecting rock samples to axial crushing. During the destruction of rock samples, both components of the electromagnetic field emitted by the rock were recorded. The paper presents the results of research on hard coal samples, presenting the obtained time domain waveforms and frequency spectrum of the emitted EM field components. Further potential uses of tests concerned with EM emitted by rocks are determined. Applications registering EM field in mine environments may provide an early mine collapse warnings.
6
Content available Stress-strain characteristics as a source of information on the destruction of rocks under the influence of load
Bogusz A., Bukowska M.
Journal of Sustainable Mining
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2015
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Vol. 14, iss. 1
46--54
EN
This paper presents the problems associated with the complete stress-strain characteristics of the destruction of rocks under load, in the full range of their strain. The most important factors influencing the course of a stress-strain curve are discussed, i.e.: the shape and size of samples and the conditions experienced when conducting the experiment in a testing machine. Presented mechanical and energy parameters were obtained in laboratory tests carried out by loading rock samples in a servo controlled testing machine as well as some indices devised on the basis of these parameters. The interpretation of complete stress-strain characteristics allow solve various issues connected with underground mining, especially assessing natural hazards which are common in underground mining for minerals, as well as designing and managing mining works within underground workings.
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