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Dynamic Properties of Sandstone Rock Subjected to Cyclic Loading15Rock mass can have a high degree of variability in rocktypes, properties and can contain extensive geologicalfeatures, such as dykes and faults, or sets ofdiscontinuities, such as bedding planes, joints, etc.Dimensions of rock mass structure are very largecompared to the maximum possible specimendimensions used under laboratory conditions. Therefore,due to inherent material variability in rock mass,laboratory results obtained from one specimen to anotherare likely to vary widely, even though the specimens mighthave been collected on nearby locations in a structure.Giving the example of the pegmatite and granodioriterock samples, Eberhardt (1998) pointed out that thoughthe pegmatite was found to have the lowest density ofthe three rock types tested; it had similar velocities tothose of the granodiorite specimens. The fact that theywere larger than expected velocities could be attributedto the much larger crystals found in the pegmatite andlarger crystals mean fewer grain boundaries, which actto reduce the velocity of the acoustic pulse. ThusEberhardt noted that in such extreme cases, physicalproperties of the individual minerals might control, orpartly control, the overall behaviour of the sample.The process of drilling and recovering core for laboratorytesting often results in sample disturbance through stressinducedmicro-fracturing, altering the physical propertiesof the rock. This disturbance may be the result ofmechanical abrasion and vibration due to the drillingprocess itself, and/or through stress relief cracking incases where the samples are retrieved from high in situstress regimes. In general, the extent of this disturbanceis often a function of drilling depth and, to a lesser degree,borehole orientation. For example, in situ stressesregimes generally increase with depth resulting in highercrack densities in the retrieved samples. Martin andStimpson (1994) noted that it then becomes possible forsamples of the same rock type, but obtained from differentin situ regimes, to have drastically different mechanicalproperties.8. CONCLUSIONThe Ostrava-Karvina coalfield (OKC) is classified as rockburst prone and having complex geo-mechanicalstructure. The sandstone rock samples studied were fromDarkov coal mine from the OKC, and they represent therock massif of a rock burst prone coal mine in the CzechRepublic. From the petro-graphic characterization,physical and geophysical properties, samples and rockspecimens are considered to embody a high degree ofsampling disturbance in terms of mineralogy, texture andstructure. This is also confirmed by various presentedrelationships between physical, geophysical and fatiguerock properties obtained through laboratory testing.Finally, it can be concluded that dynamic cyclic loadingconditions are very susceptible to rock type in terms ofmineralogy, texture and structure.ACKNOWLEDGMENTSThis work has been performed with financial grant No.105/01/0042 from Grant Agency of the Czech Republic.The study presented here is part of the Ph. D. thesissubmitted to Faculty of Mining and Geology, VSB-Technical University, Ostrava, Czech Republic, by thefirst author in the year 2004.The first author would like to take this opportunity to thankthe Czech Government for providing a scholarship topursue his doctoral study in the Czech Republic. Specialappreciation is also extended to Doc. Ing. L. Hofrichterovafrom the Department of Geophysics for her help incarrying out sonic tests, Dr. A. Kozusnikova from theInstitute of Geonics, for her help in carrying outmacroscopic petrographic analysis, and Dr. Ing. DalibarMatysek for his help in carrying out X-Ray diffractionanalysis. Thanks are due to Doc. Ing. P. Koneèný fromthe Institute of Geonics, ASCR, Ostrava for his valuablecriticism and suggestions. Thanks also belong to thelibrary staff who were of great help. Thanks also to myfriend Ing. Miloš Daniel for his programming help and toIng. P. Michalèík and Ing. O. Špinka for their help incarrying out experiments and Mrs. Hanka Kolarova forher editing help. I also wish to thank my wife Shaila andson Anurag for living without me and taking pain in theirstride and for their encouragement throughout this study.REFERENCES1. Bagde M.N. An investigation into strength and porousproperties of metamorphic rocks in the Himalayas: Acase study. Geotechnical and Geological Engineering2000;18:209-219.2. Bagde M.N. and Petros V. The effect of microstructureon fatigue behaviour of intact sandstone..Int. J. of Geosciences 2011; 2(3):240-247.3. Bagde MN, Petros V. Fatigue properties of intactsandstone samples subjected to dynamic uniaxialcyclical loading. Int. J. Rock Mech. Min Sci 2005;42:237-250.4. Bagde M.N. and Petros V. Waveform effect onfatigue properties of intact sandstone in uniaxialcyclic loading. Rock Mech Rock Eng 2005;38(3):169-196.5. Bagde M.N. and Petros V. The effect of machinebehaviour and mechanical properties of intactsandstone under static and dynamic uniaxial cyclicloading. Rock Mech Rock Eng 2005;38(1): 59-67.6. Brauner G. Rockbursts in coal mines and theirprevention. Balkema, Rotterdam, 1994:144pp.Volume 1 v No. 1 v January 2012
16 ISRM (India) Journal7. Chong C.H. and Johnson D.H. Dynamic and staticmoduli. Geophysical Research Letters1981; 8(1): 39-42.8. Eberhardt E. Brittle rock fracture and progressivedamage in uniaxial compression. Ph. D. Thesis.College of Studies and Research, Department ofGeological Sciences, University of Saskatchewan,Saskatoon, 1998:334pp.9. Eissa E.A. and Kazi A. Relation between static anddynamic Young´s moduli of rocks. Int. J. Rock Mech.Min. Sci. & Geomech. Abstr1988; 25(6): 479-482.10. Fairhurst C.E. and Hudson J.A. Draft suggestedmethod for the complete stress-strain curve for intactrock in uniaxial compression. In: International Societyfor Rock Mechanics Commission on Testing Methods,Fairhurst, C. E. and Hudson, J. A. (Co-ordinators),Int. J. Rock Mech. Min. Sci. 1999;36: 279-289.11. ISRM :Suggested methods of rock characterization,testing, and monitoring. ISRM Commisson on TestingMethods, E. T. Brown (Editor),1981; Pergamon Press,211pp.12. Konecny P, Velicka V, Snuparek R, Takla G andPtacek J. Rockbursts in the period of mining activityreduction in Ostrava-Karvina coalfield. In: 10thCongress of the ISRM–Technology Roadmap forRock Mechanics, 2003;Vol. 2, 8-12.13. Martin C.D. and Chandler N.A. The ProgressiveFracture of Lac du Bonnet granite. Int. J. Rock Mech.Min. Sci. & Geomech. Abstr. 1994;31(6): 643-659.14. McDowell P.W. Seismic Investigation for RockEngineering. In: Comprehensive Rock Engineering-Principles, Practice & Projects, Vol. 3-Rock Testingand Site Characterization, Hudson (Editor),1993;Pergamon Press, 619-634.15. Martin C.D. and Stimpson B. The effect of sampledisturbance on laboratory properties of Lac du Bonnetgranite. Can. Geotech. 1994;31: 692-702.16. Petros V, Bagde M.N., Holub K. and Michalcik P.Comparison of changes in the strength and thedeformation behaviour of rocks under static anddynamic loading. In:10 th Congress of the ISRM –Technology Roadmap for Rock Mechanics, Vol. 2,8-12 September, Sandton Convention Centre,Johannesburg, South Africa, Handley, M. and Stacey,D. (Technical Co-ordinators), The South AfricanInstitute of Mining and Metallurgy, 2003:899-902.17. Petros V. and Bagde M.N. Výzkumnapìt´opøetvárneho chování hornin pøi dynamickémnamáhání (Investigation into stress-deformationbehaviour of rock under dynamic loading). Projectreport, VSB-Technical University of Ostrava, Facultyof Mining and Geology, Institute of Mining Engineeringand Safety, Ostrava, Czech Republic, 2004, 58pp.(In czech).18. Petroš V. and Holub K. Investigation of groundvelocities during the rock bursts. ACTA MONTANAIRSM AS CR , Series A, 2003;No. 22 (129), 15-20.19. Soroush H. and Fahimifar A. Evaluation of somephysical and mechanical properties of rocks usingultrasonic pulse technique and presenting equationsbetween dynamic and static elastic constants. In: 10thCongress of the ISRM – Technology Roadmap forRock Mechanics, 2003;Vol. 2, 8-12 September,Sandton Convention Centre, Johannesburg, SouthAfrica, M. Handley and Dick Stacey (Technical Coordinators),The South African Institute of Mining andMetallurgy,1113-1118.20. Starzec P. Dynamic elastic properties of crystallinerocks from south-west Sweden. Int. J. Rock Mech.Min. Sci 1999; 36: 265-272.21. Stavrogin A.N. and Tarasov B.G. Experimentalphysics and rock mechanics. Balkema (Rotterdam),2001:356pp.22. Steblay BJ, Knejzlik J. and Koneèný P. Rock massbehaviour control during exploitation of rockburstprone coal seams-American and Czech approach andexperiences. In: Geomechanics 96, Rakowski(Editor), Balkem/Rotterdam, 1996:73-80.23. Walsh J.B. The Influence of Microstructure on RockDeformation. In: Compressive Rock Engineering -Principles, Practice & Projects, Vol .1 - Fundamentals,Hudson (Editor), 1993; Pergamon Press, 243-254.Volume 1 v No. 1 v January 2012
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