TEST YOUR KNOWLEDGE Answers on Page 32
Robert G. Font, CPG-03953
rgfont@cs.com
1. In our field work, we have recognized an erosional surface (time gap) between horizontally-lying, parallel layers of sedi- mentary rocks. What term best applies to this situation?
a) Nonconformity. b) Disconformity. c) Angular unconformity. d) Man, these questions can lead to brain deformity…
2. The formula CaSO4 describes the chemical composition of this sedimentary deposit: a) Dolomite.
b) Limestone. c) Rock salt. d) Anhydrite. e) Chemical formulae are for the birds, dude. FYI, I am not Louis Pasteur….
3. In our studies of rock mechanics and continuum mechanics concerning the theory of elasticity, the state of stress at a point in a body in a deformed state is given by the “stress tensor.” The “stress tensor” is mathematically represented by:
a) A scalar function. b) A parabola. c) A three by three matrix. d) A hyperbola. e) I take the fifth!
4. We are searching for ores of tin. Which of the following mineral compounds would best fulfill our quest? a) Ilmenite. b) Cinnabar. c) Wolframite. d) Cassiterite. e) I’d rather look for another “Rin Tin Tin”….
5. Two important equations in the Coulomb-Mohr fracture criterion are: P1 = P3 * tan2 (45o + Ø/2) + 2C * tan (45o + Ø/2) S = C + Pn * tan Ø
(1) (2)
Equation (1) expresses the relationship between the major and minor principal stresses P1 and P3 (respectively) at failure. Equation (2) defines shear strength (S) as a function of the cohesive strength (C), plus the frictional strength (Pn * tan Ø). Recall that (Pn) is the normal stress acting on the failure surface and (Ø) is the angle of internal friction. From (1) and (2) above, we may express the value of the “undrained shear strength” ((Su) and the “unconfined compressive strength” (UCS) of saturated clays, recalling that these tend to behave as purely cohesive materials with an apparent Ø = 0. What are these values?
a) Su = C and UCS = 2C b) Su = 2C and UCS = 4C c) Su = 3C and UCS = 6C d) Man, I don’t go for this kind of stuff. Just give me a rock hammer and let me play!”
32 TPG •
Oct.Nov.Dec 2017
www.aipg.org
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