Qhafor Ameen Hamasur

Chapter Three
Laboratory tests
strength was done through an equation proposed by Thuro et al. (2001) as in
Fig (3-2), which shows the shape correction for L/D ratio from 1-3 in the
calculation of UCS as follows:
UCS * = UCS (0.925+0.036*L/D) ………..(3-2)
Where: UCS * =Calculated unconfined compressive strength of an equivalent
2:1 Length/Diameter specimen.
UCS=Measured unconfined compressive strength of the specimen tested
L=Test core length (height).
D=Test core diameter.
Also due to the effect of size (core diameter) on the uniaxial compressive
strength value, the below equation (Hoek and Brown,1980) is used:
б ci (d) = б ci (50) (50/d) 0.18 ……………….(3-3)
Where: б ci (d) = Unconfined compressive strength of specimen of diameter d.
б ci (50) = Unconfined compressive strength of 50mm diameter specimen.
From the above equation, the unconfined compressive strength of 50mm
diameter specimen can be calculated, which is the acceptable size in the rock
mass classification systems.
The results of the unconfined compression test for core specimens of both
surface sections and boreholes are shown in tables (3-1) and (3-2)
respectively.
3-3-Point load test
An extensive investigation by Broch and Franklin (1972) proved that this
test has a great importance in rock mechanics and engineering geology as an
indirect measure of the UCS, and it was regarded as a standard test by the
international society of rock mechanics in 1973 (Bieniawski, 1975).
This test is widely used in practice due to easiness of the test, simplicity of
specimen preparation and possible field application (Gunsallus and Kulhawy,
1984).
The test is performed according to the procedure of Brook (1985) and
ISRM (1985).The point load test involves the compressing of a rock sample
between conical steel platens until failure occurs, Fig (3-3), in which the point
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