Engineering Rock Mechanics
28 Geological setting Figure 2.25 (a) Joints caused by rapid brittle fracture. (b) Fold caused by slow ductile deformation. Alth ...
The influence of geological factors on rocks and rock masses 29 decreasing stress at constant strain. We might be considering pr ...
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3 Stress Stress is a concept which is fundamental to rock mechanics principles and applications. For those encountering stress f ...
32 Stress -nine components of which six are independent; -values which are point properties; -values which depend on orientation ...
Stress as a point property 33 Figure 3.1 (a) Normal forces and shear forces. (b) Normal stresses and shear stresses. different n ...
34 Stress \FI AN (a) (b) Figure 3.3 (a) Arbitrary loading of any rock shape. @) The normal force, m, and the shear force, AS, ac ...
The stress components on a small cube within the rock 35 1 < / UYY Direct stress Acting on a plane normal uxx -- to the x-axi ...
36 Stress Figure 3.5 Illustration of the development of two shear stresses on each face of an infinitesimal cube. 3.6 The symmet ...
The state OF stress at a point has six independent camponents 37 If we consider the stress matrix again, we find that it is symm ...
38 Stress body subjected to given loading will depend on the orientation of the cube in the body itself. We should consider, the ...
All unsupported excavation surfaces are principal stress planes 39 shear stresses acting on them and are therefore principal str ...
40 Stress 3.10 Concluding remarks We emphasize again that stress is a tensor with six independent components. When a force, F, i ...
4 In situ stress In this chapter, we will be describing why a knowledge of in situ rock stress is important for rock engineering ...
42 In situ stress 0 u2 0 0 03 OI (a) (b) (C) Figure 4.1 (a) Principal stresses acting on a small cube. @) Principal stresses exp ...
Methods of stress determination 43 Figure 4.2 In situ stress determination in the Carmenellis granite. a fuller description of t ...
44 In situ stress such flatjack measurements have to be conducted at six different orienta- tions. Note that, in general, the re ...
Methods of stress determination 45 in Fig. 4.3, the complete state of stress can be determined from measure- ments of strain in ...
46 In situ stress r FI a tj /, ac k ttt Note identification of cancellation pressure, P, Excavation time - ' Flatjack pressure - ...
Methods OF stress determination 47 pressures are measured at the test section, i.e. downhole rather than at the surface, if poss ...
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