1. Triaxial tests were carried out on 54-mm-diameter (NX core) intact rock specimens. The applied confining nressures and the principal stress differences at failure are summrised below.
Confining pressure (MPa)
|
0
|
5.0
|
10.0
|
15.0
|
20.0
|
25.0
|
|
Principal stress difference (MPa)
|
59.5
|
87.5
|
I 16.0
|
139.5
|
167.5
|
192.5
|
Plot σ1, against σ3 at failure and determine the uniaxial compressive strength and the friction angle of the intact rock.
2. The intact rock that follows the Mohr-Coulomb failure criterion has c = 15 MPa and Φ = 27°. Estimate the uniaxial compressive strength;, the uniaxial tensile strength σ, and the Brazilian indirect tensile strength σ't. Give an estimate of the point load strength index Is(50) and suggest a realistic range for the Youngs modulus E.