International Journal of Rock Mechanics & Mining Sciences 38 (2001) 227–243 Applications of an explicit solution for the transversely isotropic circular disc compressed diametrically G.E. Exadaktylos*, K.N. Kaklis Technical University of Crete, Department of Mineral Resources Engineering, Chania GR-73100, Greece Accepted 10 October 2000 Abstract This paper focuses on the Brazilian test configuration of anisotropic rocks. The proposed methodology follows that of Pinto (ProceedingsoftheFourthISRMCong,Montreux,1979);however,itismoreaccuratesinceweadoptAmadei’smethodofanalysis (Int.J.RockMech.Min.Sci.Geomech.Abstr.33(1996)293)thataccountsfortheinfluenceofanisotropyonthestressdistribution. Inafirststep,explicitexpressionsforstressesandstrainsfortheanisotropiccirculardisccompresseddiametricallyarepresentedby employing Lekhnitskii’s formalism. It is shown that the proposed analytical solution can be effectively used as a ‘‘back-analysis’’ toolforthecharacterizationofrockelasticityandstrengthproperties.Thisisillustratedbothinthecaseofpublishedexperimental results on schist and gneiss rock types, and finally in the case of specially designed Brazilian tests on Dionysos marble. # 2001 Elsevier Science Ltd. All rights reserved. 1. Introduction Anisotropic rocks of metamorphic origin such as marbles, slates, schists, gneisses, phyllites and other, as wellas,sedimentaryrockssuchassandstones,siltstones, limestones, coal and many others, are seen to occur in many practical applications in rock engineering and rock mechanics. For example, we can mention here stability of slopes, underground excavations and bore- holes for mining, quarrying, petroleum and geothermal applications,rockcharacterizationinthelaboratoryand in situ, stress and deformation measurements in rocks and performance of natural building stones in monu- mental structures and modern building structures. Despite its importance rock anisotropy is still poorly understood and the estimation of elasticity constants andstrengthofanisotropicrocksstillremainsadifficult task [1]. In bulk specimens of rock, the mechanical properties depend not only on the properties of the individual crystals,butalsouponthewayinwhichthecrystalsare assembled. The relevant information is given by a full petrographic description which includes the mineralogi- cal composition of crystals, grains, cementing materials, and alteration products and also the grain structure and the cracks. The degree of anisotropy (aelotropy) of the stone is an important geological factor since mechanical properties depend on the direction of the loading with respect to the anisotropy axes of the rock. For example, the process of splitting of an anisotropic stone is greatly facilitated by the rift. The rift is usually parallel with the bedding and may be emphasized by the presence of fibrous or platey minerals.Theseusuallyoccupypositionswiththeirlong axis parallel to the direction of grain elongation, and thusincreasethetendencytosplitinthatdirection.Rift is a property of decorative and monumental stones that the quarryman should take into account in planning operations (Fig.1). Furthermore, the tensile strength of rock is generally stated to be less than approximately 10% of its compressive strength. Griffith’s theory predicts that the uniaxial compressive strength of rocks is eight times theuniaxialtensilestrength,whereasMurrell’sextension of the Griffith criterion gives the value of ratio of compressive strength over tensile strength equal to 12 [2]. Hence, the experimental determination of tensile strength of rocks is of great importance in current rock engineering practice regarding prevention of rock failure of underground and surface works, as well as in structural engineering practice in which the *Corresponding author. Tel.: +30-821-36450; fax: +30-821-69554. E-mail address: exadakty@mred.tuc.gr (G.E. Exadaktylos). 1365-1609/01/$-see front matter # 2001 Elsevier Science Ltd. All rights reserved. PII:S1365-1609(00)00072-1