Page 143 - Reservoir Geomechanics
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126 Reservoir geomechanics
Maximum friction
EXPLANTATION
100
SLOPE = 1.0
90
t = 0.85 s N
80
70
Shear stress, t (MPa) 60 SLOPE = 0.6
50
40
30
20
10
0
0 10 20 30 40 50 60 70 80 90 100
Normal stress, s N (MPa)
Figure 4.23. Rock mechanics tests on wide range of rocks (and plaster in a rock joint)
demonstrating that the coefficient of friction (the ratio of shear to effective normal stress) ranges
between 0.6 and 1.0 at effective confining pressures of interest here. Modified after Byerlee (1978).
normal stress, rate of slip, etc. such that the coefficient of friction is found to be within
a relatively small range:
0.6 ≤ µ ≤ 1.0 (4.41)
This relation is sometimes known as Byerlee’s law. In fact, John Jaeger, perhaps the
leading figure in rock mechanics of the twentieth century, once said: There are only
two things you need to know about friction. It is always 0.6, and it will always make a
monkey out of you.
