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Öğe An experimental investigation into the drilling and physico-mechanical properties of a rock-like brittle material(Elsevier Science Bv, 2011) Yasar, E.; Ranjith, P. G.; Viete, D. R.Energy efficiency (specific energy) and penetration rate in rock drilling processes are dependent on various operational variables (applied load, torque etc.) in addition to the physico-mechanical properties of the rock being drilled. Experimental work, using a laboratory drilling setup, was carried out to investigate the interplay between the various operational variables and the physico-mechanical properties of cement mortar, an analogue for natural rock. Unconfined Compressive Strength (UCS) tests were first performed to characterise the cement mortar. The penetration rate and specific energy were determined for various experimental drilling scenarios and correlated with the operational variables employed for these drilling scenarios and the physico-mechanical properties of the cement mortar used. The results of the experimental work demonstrate the significance of applied load and torque for both penetration rate and specific energy in drilling. Additionally, the experimental results emphasise the influence of material (rock or cement) properties on the penetration rate and specific energy in drilling. From the testing data, empirical relationships are proposed for the purpose of determination of both penetration rate and specific energy for certain operational variables, and for given UCS of the material to be drilled. (C) 2011 Elsevier B.V. All rights reserved.Öğe Influence of rock mass properties on blasting efficiency(Academic Journals, 2009) Kilic, A. M.; Yasar, E.; Erdogan, Y.; Ranjith, P. G.The purpose of this paper is to determine the influence of rock mass properties on the blasting efficiency which is ratio of the block size distribution of the rock mass to the block size distribution of the muck-pile. The proposed methodology of blasting efficiency in this study is to compare physical and mechanical properties of the rock mass and block fragmentation under the same blasting conditions in Kirka borax mine. Intact rock properties, block size of rock mass before blasting and muck pile after blasting were found to measure blasting efficiency. Firstly, intact rock properties, which are unit volume weight, water absorption, uniaxial compressive strength, tensile (Brazilian) strength, cohesion and internal friction angle, were tested for each mining bench. Secondly, block sizes of rock masses in respect to discontinuity boundaries were measured and muck pile photos were taken in order to determine Block Fragmentation (BF) which is to separate the rock mass block size by blasting and that of the corresponding muck pile. Thirdly, statistical analysis between rock mass properties and block fragmentation were developed and these analysis test results have shown that a good relation between block fragmentation and Brazilian tensile strength and internal friction angle were found. As a result, block fragmentation in the same blasting conditions and other rock properties can be estimated from the best empirical correlations with the rock properties.Öğe Physico-mechanical behaviour of southeastern Melbourne sedimentary rocks(Pergamon-Elsevier Science Ltd, 2010) Yasar, E.; Ranjith, P. G.; Perera, M. S. A.[Abstract Not Available]Öğe Sand production during the extrusion of hydrocarbons from geological formations: A review(Elsevier Science Bv, 2014) Ranjith, P. G.; Perera, M. S. A.; Perera, W. K. G.; Choi, S. K.; Yasar, E.The petroleum industry spends millions of dollars each year to prevent and overcome sand control problems and their prediction has therefore become essential to minimize the adverse effects of sand production. This paper reviews existing experimental and modelling studies of the prediction of sand production. In experimental studies, the trapdoor system has been commonly used. The early experimental set-ups had a simple trapdoor configuration with a fluid inlet port to inject a single fluid to conduct qualitative tests. Other facilities were added over time, including facilities to conduct qualitative and quantitative tests, inject radial, axial and multiphase fluids and conduct tests in uniaxial and tri-axial stress environments. Experimental findings on sand production can be categorized into four different effects: the flowing fluid characteristics effect, the material characteristics effect, the loading effect, and the outlet size effect. However, the application of laboratory findings to field conditions has become doubtful due to the various assumptions used in laboratory studies, including the scaling down of the reservoir, the use of sieved river sands and/or synthetic samples, and the use of limited combinations of two-phase flows. In model development, some basic mechanisms have been recognized as responsible for sand production: shear and tensile failure, the critical pressure gradient and drawdown pressure, and erosion. Tensile failure occurs when the effective minimum principle stress applying on the rock mass reaches its tensile strength, and shear failure occurs when the applied stress on some planes in the wellbore area is higher than their bearing capacity. Reduction of reservoir pressure causes the effective hydrostatic stresses on it to be increased, breaking its pore structure, and the rock formation can be eroded internally and externally, producing sand by dynamic seepage drag forces. To date, both continuum and discrete element method (DEM) approaches have been considered in sand production models. Most approaches have been developed considering the hydro-mechanical or shear failure mechanisms and some have combined them. (c) 2014 Elsevier B.V. All rights reserved.
