Laboratory testing of a long expansion rock bolt support for energy-absorbing applications

The properties of anchored surrounding rock may vary considerably under complex geological and stress conditions, especially dynamic loading in deep mining. Therefore, comprehensive study of the reinforced mechanism is required to prevent failures associated with deep mining. In this paper, with sandstone as matrix and steel bar as bolt, the dynamic compression test of reinforced rock was carried out by using a 50 mm rod diameter split Hopkinson pressure bar (SHPB) test device. The mechanical and energy characteristics of reinforced rock under dynamic loading were analyzed. The results show that the dynamic strength of reinforced sample is greater than that of unreinforced sample and increases with the increase of the strain rate. The reflected energy and absorbed energy increase with the increase of incident energy, while the transmitted energy increases slightly. The higher the strain rate, the larger the energy dissipation rate and the higher the degree of fragmentation. It shows that the energy dissipation characteristic reflects the internal damage process to some extent. Compared with the results of unreinforced samples, the reflected energy of reinforced samples significantly increases and the absorbed energy will significantly decrease. It can be seen that the bolt can reduce absorbed energy of surrounding rock, thereby improving the stability of roadway surrounding rock. The results may provide reference for the stability of deep roadway and support design.

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“…According to the energy balance [27], the absorbed energy of rock during impact loading can be calculated using the following equation [28]:…”

Section: Energy Calculationmentioning

confidence: 99%

Experimental Research on Mechanical and Energy Characteristics of Reinforced Rock under Dynamic Loading

Xin-xi

Liu

Zhao

et al. 2019

Shock and Vibration

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“…The variety of conditions in which the rock bolt support is used makes it suitable for securing the stability of the excavation or as reinforcement of existing rock bolt support [3]. Choice of rock bolt support in "Olkusz -Pomorzany" mine is based on the determination of roof's class which is determined on the basis of the results of geomechanical tests and on the basis evaluation of weakness factor of rock mass "c" carried out by an expert [4].…”

Section: Choice Of Rock Bolt Supportmentioning

confidence: 99%

“…Currently underground exploitation is carried out in three mines "Rudna", "Polkowice -Sieroszowice" and "Lubin" of Legnica-Głogów Copper District (LGOM), that belong to KGHM Polish Copper SA. The basic type of rock mass reinforcement method for both preparatory and operational excavations in underground metal ore mines, both in Poland and in different countries across the world, is the expansion shell or adhesive-bonded rock bolt [3,6,8]. The annual consumption of rock bolt supports in Polish ore mining is more than 3 million units (Tab.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of Rock Bolt Support for Polish Hard Rock Mines

Skrzypkowski

2018

E3S Web Conf.

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Abstract.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. Key words -point resin rock bolt support, roof class, ore mining.

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“…Generally, the accumulation of elastic energy results from gravitational stress (E gravity ), tectonic stress (E tectonic ), concentrated stress (E concentrated ), and dynamic stress (E dynamic ) [9,40]. Hence, the complete balanced equation for energy in an underground coal body can be written as follows [40]:…”

Section: Energy Forms and The Energy Conservation Equationmentioning

confidence: 99%

Analysis of Energy Accumulation and Dissipation of Coal Bursts

et al. 2018

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Coal bursts are a serious dynamic hazard for underground coalmines, and they attract the extensive interest of studies from mining and geotechnical researchers worldwide. More recently, coal-burst incidents were reported in some Australian coalmines as a result of inadequate geological assessment of coal-burst hazards. The coal-burst process is closely associated with the accumulation of elastic energy and the rapid dissipation of kinetic energy. This paper introduces the essential geological conditions for energy accumulation, and the likely precursors for rapid energy dissipation leading to coal burst, which can be used by Australian coalmines to determine their coal-burst risk accordingly. Different energy forms and their transformations during the coal-burst process are introduced in detail in this paper. The dominant geological factors resulting in the accumulation of massive energy are analyzed, and the likely precursors associated with the instant release of elastic energy are discussed.Energies 2018, 11, 1816 2 of 10 diminish the damage of potential coal-burst accidents following the first recognized case of coal burst accident at a coalmine. However, the risk of coal burst is generally hard to recognize for coalmines with no history of coal burst. Particularly in Australian coalmines, coal-burst hazards are hard to recognize, as there is no pre-assessment process or real-time monitoring apparatus of coal-burst risk.Energy concepts associated with coal bursts are a hotspot of coal-burst research. Based on the mechanical behavior of coal subject to uniaxial compression stress, Bieniawsk et al. found that coal bursts only happen when a large amount of elastic energy is stored in the body of coal [15]. Many researchers carried out detailed research on the energy dissipation forms of coal bursts, and proposed various coal-burst monitoring and early-warning methods, such as electromagnetic radiation [16], acoustic emission [17], and microseismic techniques [18][19][20]. L.M. Dou believes that the key to mitigating coal bursts is a decrease in the elastic energy stored in the coal or surrounding rock of the mining area [21]. In other words, coal bursts only happen when massive elastic energy stored in the coal is instantaneously released. This paper aims to introduce the essential geological conditions for energy accumulation, and the likely precursors for rapid energy dissipation in coalmines, which can assist Australian coalmines in determining their coal-burst risk accordingly. To achieve this aim, various energy forms and energy balances featured during coal bursts are introduced in detail. Then, the dominant geological factors resulting in the accumulation of massive energy are analyzed. Furthermore, the likely precursors associated with the instant release of elastic energy are discussed.

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Laboratory testing of a long expansion rock bolt support for energy-absorbing applications

Cited by 20 publications

References 11 publications

Experimental Research on Mechanical and Energy Characteristics of Reinforced Rock under Dynamic Loading

Experimental Research on Mechanical and Energy Characteristics of Reinforced Rock under Dynamic Loading

Evaluation of Rock Bolt Support for Polish Hard Rock Mines

Analysis of Energy Accumulation and Dissipation of Coal Bursts

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