Use of the Boussinesq equation for determining the distribution of stress within a diametrical point load test

Citation
Ms. Al-derbi et Mh. De Freitas, Use of the Boussinesq equation for determining the distribution of stress within a diametrical point load test, ROCK MECH R, 32(4), 1999, pp. 257-265
Citations number
8
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Geological Petroleum & Minig Engineering
Journal title
ROCK MECHANICS AND ROCK ENGINEERING
ISSN journal
0723-2632 → ACNP
Volume
32
Issue
4
Year of publication
1999
Pages
257 - 265
Database
ISI
SICI code
0723-2632(199910/12)32:4<257:UOTBEF>2.0.ZU;2-#
Abstract
The maximum tensile stress at failure for a dry specimen, as determined by the Boussinesq equation for the diametrical point load test, was found to b e in very good agreement with the diametrical point load tensile strength ( Is) as defined by ISRM (1985). The force at failure for specimens of differ ent geometry was used to determine the stress distribution along the line o f loading. Distinctive tensile stress gradients dominate almost 84 percent of the specimen radius regardless of the size of the specimen. The maximum tensile stress is located away from the centre of the specimen at a distanc e approximately 76 percent along the specimen radius, measured from the cen tre. The stress magnitude at the centre of the specimen is small and repres ents about 13 percent of the maximum tensile stress calculated, which sugge sts that the initiation of the fracture is not from the specimen centre. At the zone of contact between the specimen and the loading cones there exist s great compressive stress in areas where much material destruction occurs under the loading platen cones. The value of this compressive stress varies from specimen to specimen and, for the material used in these experiments (Oolitic limestone), ranges from 5.3 to 7.2 times the dry unconfined compre ssive strength of the material. According to the ISRM Suggested Method for Point Load Test, Is((50)) is approximately 0.8 times the uniaxial tensile s trength. The maximum tensile stress revealed by the Boussinesq equation (Bs ) was correlated with Is((50)) and found to be in the order of 0.9 times th e uniaxial tensile strength.