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    An innovative and effective approach to hard rock cutting
    (Crc Press-Balkema, 2016) Erarslan, N.; Ghamgosar, M.
    One of the most important problems of hard rock cutting machines is machines are able to cut the rocks having strength up to a certain value (e.g. 250MPa) with very high energy costs. This study will find applications in many engineering areas such as mining, tunnelling and drilling etc. This research focuses on 'fatigue of rock/granular material' and its technical application in hard rock cutting machinery and mining. Oscillating Disc Cutting (ODC) - Australia technology has been developed with the latest technology in this field in the world and is capable of breaking very hard rock, with strength up to 350MPa, at acceptable-to-good excavation rates by using 70% less cutting forces and energy compared with the standard hard rock cutting machines. Of course there are many rock cutting parameters including machine parameters such as attack angle of cutters and torque values etc. and rock parameters such as rock strength and brittleness etc. However, this research just focuses on the behaviour of the rock-tool interaction zone under various cyclic loading types. Research results showed the developed Fracture Process Zone (FPZ) under cyclic loading is much bigger than the FPZ developed under monotonic loading even with the use of lower forces.
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    An innovative and effective approach to hard rock cutting
    (International Society for Rock Mechanics, 2016) Erarslan, N.; Ghamgosar, M.
    One of the most important problems of hard rock cutting machines is machines are able to cut the rocks having strength up to a certain value (e.g. 250 MPa) with very high energy costs. This study will find applications in many engineering areas such as mining, tunnelling and drilling etc. This research focuses on 'fatigue of rock/granular material' and its technical application in hard rock cutting machinery and mining. Oscillating Disc Cutting (ODC) - Australia technology has been developed with the latest technology in this field in the world and is capable of breaking very hard rock, with strength up to 350 MPa, at acceptable-to-good excavation rates by using 70% less cutting forces and energy compared with the standard hard rock cutting machines. Of course there are many rock cutting parameters including machine parameters such as attack angle of cutters and torque values etc. and rock parameters such as rock strength and brittleness etc. However, this research just focuses on the behaviour of the rock-tool interaction zone under various cyclic loading types. Research results showed the developed Fracture Process Zone (FPZ) under cyclic loading is much bigger than the FPZ developed under monotonic loading even with the use of lower forces. © 2016 Taylor & Francis Group, London, ISBN 978-1-138-03265-1
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    Experimental and numerical investitaions on mixed mode fracturing of concrete and rocks by using semi-Circular Disc (SCD) and Disc Specimens
    (American Rock Mechanics Association (ARMA), 2015) Erarslan, N.; Obligado, R.; Li, Z.; Ghamgosar, M.
    Sudden and violent fracturing of brittle materials, such as natural-forming rocks and artificial aggregates like concretes, still remain one of the leading causes of fatalities in mining, civil and geotechnical industries today. The primary aim of this research work is to investigate the mixed modes I (tensile) and II (shearing) fracturing mechanisms of Brisbane Tuff rock and prepared concrete samples using Semi-Circular Disc (SCD) and Cracked Chevron-Notched Brazilian Disk (CCNBD) specimen geometries. In order to create various mixed mode loading conditions, the chevron notch cracks of the CCNBD specimens were oriented at notch crack inclination angles, ?, of 0°, 30°, 45°, and 70° as part of the diametral testing procedure, whilst the SCB specimens were cut at the same ?s prior to conducting the three-point bending tests. The experimental study revealed that the CCNBD geometry and the Brisbane Tuff rock have higher failure loads than the SCD geometry and concrete sample counterparts. Following the experiments, a series of numerical analyses were then performed using FRANC2D software to simulate the stress distributions and fracturing behaviour of the samples at different ? values. Overall, this investigation showed ?, and hence the mixed mode loading condition, is a function of failure load, stress distributions, position of the pre-existing cracks relative to the major principal stress and fracturing behaviour of brittle materials. Copyright 2015 ARMA, American Rock Mechanics Association.
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    Experimental and Numerical Studies on Development of Fracture Process Zone (FPZ) in Rocks under Cyclic and Static Loadings
    (Springer Wien, 2016) Ghamgosar, M.; Erarslan, N.
    The development of fracture process zones (FPZ) in the Cracked Chevron Notched Brazilian Disc (CCNBD) monsonite and Brisbane tuff specimens was investigated to evaluate the mechanical behaviour of brittle rocks under static and various cyclic loadings. An FPZ is a region that involves different types of damage around the pre-existing and/or stress-induced crack tips in engineering materials. This highly damaged area includes micro- and meso-cracks, which emerge prior to the main fracture growth or extension and ultimately coalescence to macrofractures, leading to the failure. The experiments and numerical simulations were designed for this study to investigate the following features of FPZ in rocks: (1) ligament connections and (2) microcracking and its coalescence in FPZ. A Computed Tomography (CT) scan technique was also used to investigate the FPZ behaviour in selected rock specimens. The CT scan results showed that the fracturing velocity is entirely dependent on the appropriate amount of fracture energy absorbed in rock specimens due to the change of frequency and amplitudes of the dynamic loading. Extended Finite Element Method (XFEM) was used to compute the displacements, tensile stress distribution and plastic energy dissipation around the propagating crack tip in FPZ. One of the most important observations, the shape of FPZ and its extension around the crack tip, was made using numerical and experimental results, which supported the CT scan results. When the static rupture and the cyclic rupture were compared, the main differences are twofold: (1) the number of fragments produced is much greater under cyclic loading than under static loading, and (2) intergranular cracks are formed due to particle breakage under cyclic loading compared with smooth and bright cracks along cleavage planes under static loading.
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    Experimental Investigation of Fracture Process Zone in Rocks Damaged Under Cyclic Loadings
    (Springer, 2017) Ghamgosar, M.; Erarslan, N.; Williams, D. J.
    Compared with other materials, most rocks generally fail in a brittle fashion rather than exhibiting yielding or purely plastic deformation. However, the initiation and coalescence of micro-cracks in the nonlinear region, known as the 'fracture process zone' (FPZ), are the primary reason for fracture propagation in rocks. Different elasticity-related models proposed for determining the features of the FPZ have not achieved an adequate understanding of its various fracture patterns. Based on previous experiments and numerical models, micro-crack density has been shown to be a function of loading history and to vary depending on whether the loading is monotonic or cyclic. The aim of the study reported here was to examine the different patterns of the FPZ under various types of cyclic loading and to quantitatively define damage and fracture patterns through the grains or rock matrix. Considerable laboratory testing was conducted, and fractured samples were investigated by computerised tomography scanning, supported by thin-section analysis. In the study, two different types of cyclic loading were tested: stepped and continuous. A diametral compressive loading was applied at predetermined amplitude and frequency with the continuous cyclic loading. The applied cyclic diametral compressive load was returned to the original level after each step, and at the next step, the amplitude started from zero, with stepped cyclic loading (SCL). An average 30 % strength reduction was found due to the SCL and emergence of high micro-fracture density in the FPZ. We presume that hard rock breakage techniques will be improved, especially for rock-cutting technologies, such as drag bits and oscillating disc cutting, by understanding the effects of cyclic loading on rock strength.
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    Laboratory investigations of fracture toughness and tensile strength for various rock types
    (Crc Press-Balkema, 2016) Ghamgosar, M.; Erarslan, N.; Tehrani, K.
    Microfractures and discontinuities are the common structural features of the rock mass lead initiating and developing the brittle fractures in rocks. Fracture toughness is an intrinsic material property for the pre-exist cracks initiate fracture development and play a significant role in brittle fracturing. The Cracked Chevron-Notched Brazilian Disc (CCNBD) samples were tested to determine the fracture toughness of monsonite and sandstone samples. Since conducting fracture toughness tests are quite hard compared with the Brazilian test, the tensile strength can be determined by using the tensile fracturing parameters of rocks. Moreover, stress analysis obtained from the Extended Finite Element (XFEM) modelling confirmed a comprehensive relationship between tensile strength and tensile fracturing parameters of rocks. Based on the laboratory experiments, the tensile strength o f rocks can be used for the modelling of tensile fracturing and this will improve our understanding of rock fracturing behaviour utilising for the rock cutting and mining designs.
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    Laboratory investigations of fracture toughness and tensile strength for various rock types
    (International Society for Rock Mechanics, 2016) Ghamgosar, M.; Erarslan, N.; Tehrani, K.
    Microfractures and discontinuities are the common structural features of the rock mass lead initiating and developing the brittle fractures in rocks. Fracture toughness is an intrinsic material property for the pre-exist cracks initiate fracture development and play a significant role in brittle fracturing. The Cracked Chevron-Notched Brazilian Disc (CCNBD) samples were tested to determine the fracture toughness of monsonite and sandstone samples. Since conducting fracture toughness tests are quite hard compared with the Brazilian test, the tensile strength can be determined by using the tensile fracturing parameters of rocks. Moreover, stress analysis obtained from the Extended Finite Element (XFEM) modelling confirmed a comprehensive relationship between tensile strength and tensile fracturing parameters of rocks. Based on the laboratory experiments, the tensile strength of rocks can be used for the modelling of tensile fracturing and this will improve our understanding of rock fracturing behaviour utilising for the rock cutting and mining designs. © 2016 Taylor & Francis Group, London
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    Viability assessment of cerchar abrasivity test for the anisotropic brisbane rocks
    (International Society for Rock Mechanics, 2015) Erarslan, N.; Ghamgosar, M.
    With the increased use of mechanized rock excavation, there have been developed internationally a number of methods to assess the abrasivity of rock materials. These methods range from determination of abrasive and hard mineral content using petrographic thin section analysis to weight loss or rate of wear flat development on specified test pieces. The Cerchar abrasivity index (CAI) test has been widely accepted for the assessment of rock abrasiveness and is determined as the abrasion of a steel pin after scratching over the freshly-broken or saw-cut surface of a rock. Two types of testing devices are in use today: (i) the original 'Cerchar apparatus', and (ii) the 'West apparatus', which was adopted herein. The CAI is calculated from the measured diameter of the resulting wear flat on the steel pin after 10mm scratching. This test has been considered to provide a reliable indication of rock abrasiveness for isotropic rocks. However, a great amount of rocks in natureis anisotropic. Phyllite is an anisotropic and foliated metamorphic rock and various types of phyllite specimens were tested in this research. Although phyllite is a type of rock primarily composed of quartz and the expected CAI value can be high, mechanical cutting of this rock should not be very problematic compared with igneous rocks have same CAI value. As phyllite is a foliated metamorphic rock, most of the specimens split into sheets through the quartz seam by the tip during scratching normal to the axis of quartz seams. Hence, viability assessment of Cerchar abrasivity test and F-Schimazek index values for the anisotropic rocks is investigated in this research. © 2015 by the Canadian Institute of Mining, Metallurgy & Petroleum and ISRM.