Engineering Rock Mechanics
348 Underground excavation instabilijl mechanisms nature of stress has to be considered, but in CHILE materials there is a relat ...
Stress-controlled instability mechanisms 349 79.2.7 Stresses and displucements around a circular excavation In rock mechanics an ...
350 Underground excavation instabiliiy mechanisms OJD.. I Boundarv stresses at e = 0" and 180" 1 t = 90" and 2fO": (To = ~~(3k-l ...
Stress-controlled instabiliv mechanisms 35 1 From these equations we can see that: (a) when p = p,, the internal pressure replac ...
352 Underground excavation instability mechanisms the lower mass of rock is replaced with a statically equivalent force p,A, whe ...
Stress-controlled instability mechanisms 353 redistribution over 10 tunnel diameters is shown in Fig. 19.13. Other interesting s ...
354 Underground excavation instability mechanisms maximum stress concentration is minimized. Fig. 19.17 shows how the stress con ...
Stress -con trolled instability mechanisms 355 = - P ((1 + k)[(l + 42) + (1 - q2) COS 2 (x - PI] 2q -(1 - k)[(l + q)2 cos2x + ...
356 Underground excavation instability mechanisms 14 12 '.. '., Figure 19.17 Optimal aspect ratio for an elliptical excavation ...
Stress-controlled instability mechanisms 357 Figure 19.18 Elliptical openings in transversely isotropic rock. Slip on pre-existi ...
358 Underground excavation instabiliv mechanisms Mohr - Coulomb criterion for the intact rock 1 + sin 0 Criterion for fractured ...
A note on tirne-dependency and weathering 359 possibility of discrete blocks developing as a consequence. This is especially lik ...
360 Underground excavation instability mechanisms There are index tests which assist in characterizing aspects of weather- ing, ...
Design and 20 analysis of u n der g ro u n d excavations In Chapter 19, we concentrated on the specific instability mechanisms r ...
362 Design and analysis of underground excavations If possible, design with the rock Figure 20.1 Assessing roof and sidewall str ...
Design against structurally-controlled instability 363 Figure 20.2 The effect of excavation orientation in relation to discontin ...
364 Design and analysis OF underground excavations 1 When the strata thin upwards, replace y in these equations with yo: When a ...
Design against structurally-controlled instability 365 The principle of the voussoir arch is open to some discussion, but a bloc ...
366 of the arch is such that excessive inter-block compressive stress is generated, then instability will arise because the stre ...
Design against structural/y-contro//~ instability 367 e zone I Figure 20.7 Simple model of rock bolts in stratified roofs. the e ...
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