1、翻译部分英文原文Experimental, numerical and analytical studies on tensile strength of rocksNazife Erarslan , DavidJohnWilliamsGolderGeomechanics Centre, School of Civil Engineering, TheUniversity of Queensland, Brisbane, Qld 4072, AustraliaAbstract: The difculties associated with performing a direct uniaxia
2、l tensile test on a rock specimen have led toa number of indirect methods for assessing the tensile strength. This study compares experimentalresults of direct and indirect tensile tests carried out on three rock types: Brisbane tuff, granite andsandstone. Thestandard Brazilian indirect tensile test
3、caused catastrophic crushing failure of the diskspecimens, due to the stress concentration produced by the line loading applied and exacerbated by thebrittleness of the rock tested, rather than the expected tensile splitting failure initiated by a centralcrack. This nding led to an investigation of
4、the effect of loading conditions on the failure of Braziliandisk specimens using three steel loading arcs of different angle applied to three different rock types,using numerical modeling and analytical results. Numerical modeling studies were also performed toinvestigate theeffect of a pre-existing
5、 crack on the stress distribution within Brazilian disk specimens.It was found that there is substantially higher tensile stress concentration at the center of the disk witha pre-existing crack compared with that for a disk without a pre-existing crack. The maximum stressintensity factor (fracture t
6、oughness) values at the tip of the central pre-existing cracks were determinedfrom numerical modeling and compared with fracture toughness values obtained experimentally forthe three rock types. It was concluded that a 20loading arc gives the best estimate of the indirecttensile strength.Keywords:Br
7、azilian test;Direct tensile strength of rock;FRANC2D;Indirect tensile strength of rock;Pre-existing crack.1IntroductionThe difculties associated with performing a direct uniaxialtensile test on a rock specimen have led to a number of indirectmethods for assessing the tensile strength. In 1978, the B
8、raziliantest was ofcially proposed by the International Society for RockMechanics (ISRM) as a suggested method for determining thetensile strength of rock materials 1. The Brazilian test, orsplitting tension test, isperformed by applying a concentratedcompressive load across the diameter of a disk s
9、pecimen. TheBrazilian test is also a suggested method for determining thetensile strength of concrete materials.The Brazilian test has been criticized since itwas initiallyproposed. Fairhurst 2 first discussed the important issue of thevalidity of the Brazilian test. He stated that failure may occur
10、away from the center of the test disk for small angles of loadingcontact area and also thecalculated tensile strength from aBrazilian test is lower than the true value of thetensile strength.Hondros 3 developed an approach to measure the elasticmodulusand Poissons ratio using a Brazilian disk, and a
11、lsoformulated a complete stresssolution for the case of a radialload distributed over a nite circular arc of the disk.Although the Brazilian test has been studied extensively, bothexperimentallyand theoretically, relatively little attention havebeen directed towards researchingthe validity of the te
12、st. Severalkey questions remain unresolved: for example, how to guaranteecrack initiation at the center of the specimen (beneath theconcentratedload), how to obtain an accurate representation ofthe tensile strength of the rockfrom the test, and how to obtainclosed-form expressions for the complete s
13、tressand strain eldsboth for the Brazilian tests and for the case when the load isapplied as a pressure acting normal to and uniformly across an arcof nite length. Hudson et al. 4 found that the tensile strength ofrock varies considerably whenmeasured by different methodsand that the heterogeneity o
14、f the rock tested and the contactcondition between the specimen and the steel platens of thetesting machinewill inuence the tensile strength value obtained.He observed that, In the Brazilian test, it was found that failurealways initiated directly under the loading points if at steelplatens were use
15、d to load the specimen, which actually invali-dates the test for the determination of tensile strength. Wanget al. 5 used specimens with two parallel at ends at the loadingpoints to prevent local crack initiation at the loading points. However, they found that the atness and parallelness of the aten
16、ds are critical for a successful test.The classical theory 1 assumed that the concentrated load isapplied over an innitesimally small width as a line load, butclearly this would lead to stresses of very high intensity. Theactual loads are not concentrated but are distributed over nitearc of the disk. The tensile strength of a rock disk specimen iscalculated using the equation:（1）where P is the failure load, and d and t are the
