1. (Part 32, PP 2007, animation+p/r : 2009.02.27 rev 2012.04.18)
Part Rock mass composition, its strength in tunneling practice on Iceland and Turkey
VIII-2008 Essen / V-2012
(Part 32, PP 2007, animation+p/r : rev )
Copyright notice Unauthorised copying of this presentation as whole or in parts in any form or by any means, electronic, photocopying, recording or otherwise, without prior written permision is prohibited.
ready

2. Where are you ???
ready

3. Nord-America Plate
Eurasia Plate
ready

4. 4 Icelandic geology 4 2 cm/year 2 cm/year Nord-America Plate
Eurasia Plate
press
ready
Icelandic geology 4 4

5. Geologic Time Scale
Iceland
ready

6. 20 - 30 millions 2 millions 2008 4.7 billion years =70 years press
ready
2 hours
2 days

7. Icelandic Rock Types
press
ready

8. Eruption fissures and dikes
press
press
ready
Eruption fissures and dikes

9. Moss covered lava – a common Icelandic landscape
ready
Moss covered lava – a common Icelandic landscape

10. Rock “material” — strong, stiff, brittle:
Weak rock > Strong concrete.
Strong in compression, weak in tension.
Post-peak strength is low unless confined.
Rock “mass” — behavior controlled by discontinuities:
Rock mass strength is 1/2 to 1/10 of rock material strength.
Discontinuities give rock masses scale effects.
press
ready

11. Unit Weights of Rocks
ready

12. Intact Rock Strength Interrelationships
ready

13. ER-qu Groups for Igneous Rocks
ready
Deere and Miller (1966)

14. Typical geological problems in tunnelling works
Rock instability.
Karst cavities.
Soft ground and fault zones.
Heavy water ingress.
ready

15. Overbreaks in TBM tunnel
Collapsing tunnel wall in D&B section
ready

16. Overbreak, ribbs and netting
ready

17. Jökulsa Diversion Tunnel - rock falling down in front
of cutter head and overbreak
ready

18. Rock falling down from the fault and overbreak
ready

19. Collapsing tunnel wall in TBM section
ready

20. Karst topography in limestone is formed by a chemical dissolution process when the groundwater circulates through the limestone.
Carbon dioxide from the atmosphere is fixed or converted in the soil in an aqueous state and combined with rain water to form carbonic acid, which dissolves carbonate rock.
Karstic features develop from a self- accelerating process of water flow along well- defined pathways such a bedding planes, joints and faults.
As the water percolates downward under the force of gravity, it dissolves and enlarges the pathways.
Enlargement of a pathway allows more water flow which increases the dissolution rate.
Siow Meng Tan 2006
press
press
press
ready
* karst - a geologic terrain or surface landscape with distinctive characteristics of relief and drainage arising primarily from dissolution of rock (or soils) by natural waters. Karstic terrains are underlain by rocks that have undergone significant dissolution by groundwater flow and are characterized by: (1) closed depressions of various size and arrangement, (2) disrupted surface drainage, and (3) caves and underground drainage systems. 20 20

21. NW corner of Iceland close to Ísafjörður
press
press
ready

22. None groutable rock- note small pieces of cement grout
PU grouted sandstone
PU grouted pores in scoria
press
ready

23. Water supply into Icelandic rock mass:
- Ólafsfjörður Tunnel
ready

24. Rock masses with few discontinuities, or
Massive rock:
Rock masses with few discontinuities, or
Excavation dimension < discontinuity spacing
Jointed or “blocky” rock:
Rock masses with moderate number of discontinuities
Excavation dimension > discontinuity spacing
Heavily jointed rock:
Rock masses with a large number of discontinuities
Excavation dimension >> discontinuity spacing
press
press
ready

25. Rock Fracture - Orientation
Single set of planes of weakness Stability is a function of excavation axis:
- Maximize - strike perpendicular.
- Minimize - strike parallel.
More typically multiple sets of planes of weaknesses:
- Maximize by avoiding having any strike close to parallel to axis.
press
press
ready

26. Larger excavation -> increased potential for blocky fall-out!!
Rock Fracture – Size / Scale Effects
Larger excavation -> increased potential for blocky fall-out!!
press
ready

27. Excavation results in stress redistribution at perimeter:
High & Low Stress
Excavation results in stress redistribution at perimeter:
- Low Stress or Tension: mobilized shear strength will be low - Failure!
- High Stress: locally, tangential stresses may exceed rock strength - Failure!
Above conditions can result in fall-out (walls, crown)
- Geometry of fall-out material a key consideration.
- Ideally eliminate or limit the zones of both high and low stress around the perimeter.
press
ready

28. High-Stress Failure Zones
Not always practical to have circular/elliptical sections
most convenient.
Stress concentration will occur as a function of stress field/orientation and excavation shape.
Shaded areas show where rock burst or yield is most likely to occur around a horseshoe opening under three types of principal stress orientation:
- Vertical.
- Horizontal.
- Inclined.
press
press
ready

29. Stress distribution in excavation areas
press
ready

30. Some types of behaviour types in underground openings (partly from Martin et al., 1999 and Hoek et al., 1995)
press
ready

31. Rock stable
ready

32. Block fall(s)
ready

33. Cave-in
ready

34. Buckling
ready

35. (ravelling)
ready
Rupturing

36. Slabbing
ready

37. Rock burst
120 cm
ready

38. Squeezing or swelling ground
ready

39. Main principles in the process of ground characterization
Empirical and
classification
methods
Geology
and ground
characterization
Numerical
analyses and other
calculations
Rock engineering
and design
Observational
methods
Main principles in the process of ground characterization
and rock engineering (Stille, Palmström 2003)
press
press
ready

40. Tunneling methods
D&B
TBM
ready

41. press
press
press
ready

42. Deformations of D&B and TBM tunnels
press
ready

43. Preparations for blasting Fractured rock after blasting
The influence of blasting
on the surrounding rock
( Palmstrom and Singh, 2001)
ready

44. Early Site Investigation Objectives
(reduce uncertainties):
Rock - intact rock strengths.
Stress - In-Situ Stress levels/orientations.
Fracture – discontinuities!!!
Water – head, permeability, estimates flow locations and rates.
Fault visible at the surface
press
ready

45. Some of these empirical design systems include:
Rock mass classification systems are important because they provide a consistent means of describing quantitatively the rock mass quality. This in turn has led to the development of many empirical design systems involving rock masses. 
Some of these empirical design systems include:
Open slope (face) span and support design.
Man-entry slope span design.
Tunneling support design.
Pillar design.
Cutter head cuttability assessment.
Rock slope design.
Underground excavation stand-up time.
Suitability for block caving.
press
ready

46. Empirical design methods
Appropriate during feasibility assessments.
Require classification of the rock mass.
Most commonly used today:
- Bieniawski RMR rating.
- NGI Q rating.
ready

47. The Q or NGI system was based on tunnelling.
KEY POINTS
Rock mass rating systems are a useful way of forming an evaluation of rock masses.
The Q or NGI system was based on tunnelling.
The RMR (CSIR) system is more commonly used for slope stability.
The strength of rock masses can be judged from these systems.
ready

48. NGI - Q Rating of Rock Masses
Q-Rating based on 6 parameters:
Rock Quality Designation, RQD
Number of Joint Sets, Jn
Roughness of Discontinuities, Jr
Discontinuity Condition/Filling, Ja
Groundwater Conditions, Jw
Stress Reduction Factor, SRF
Rating of Rock Formation:
press
ready

49. ? Table 1. Rock Mass Classification based on RQD RQD
Rock Quality Classification
<25%
Very Poor
25-50%
Poor
50-75%
Fair
75-90%
Good
90-100%
Excellent
press
ready

50. ready

51. Rock Quality Assumptions
Q= One joint set; rough, irregular, undulating joints with tightly healed, hard, non-softening, impermeable filling; dry or minor water inflow; high stress, very tight structure.
Q=3
- Two joint sets plus misc.; smooth to slickensided, undulating joints; slightly altered joint walls, some silty or sandy clay coatings; medium water inflows, single weakness zones.
Q=0.1
- Three joint sets; slickensided, planar joints with softening or clay coatings; large water inflows; single weakness zones.
press
press
ready
Q=100
Q=3
Q=0.1

52. Tunnel Support
Lining, e.g. shotcrete
Rock bolts
ready

53. Equivalent dimension = Span, Diameter or Height [m] /ESR = ?
- based on Q (RQD) value
Equivalent dimension = Span, Diameter or Height [m] /ESR = ?
ready

54. Tunnels and the Q rating ESR Values (Barton et al 1974)
Require De and ESR:
De = equivalent dimension
= ratio of excavation span or height to ESR
ESR = excavation support ratio
ESR = fn (the tunnel use & level of risk chosen)
ESR Values (Barton et al 1974)
Temporary mine openings
3 - 5
Permanent mine openings, water tunnels for hydro power, etc.
Power stations, major road & railway tunnels, etc. 1
Underground nuclear power stations, railway stations, etc.
0.8
press
ready

55. Tunnel supports and the Q ratingDE
Shotcrete thickness
press Q
press
press
ready

56. Example:
10 m span, ESR = 1
Q = 1.0
ready

57. ? Rock bolt Spacing vs. Rock Quality
The data basis used in the Q system for rock bolt spacing
where shotcrete is not installed (Palmstrom and Broch, 2006).
ready

58. The relation between grout-takes (kg/tunnel-m) and Q-value
Q-Rating based on 6 parameters:
Rock Quality Designation, RQD
Number of Joint Sets, Jn
Roughness of Discontinuities, Jr
Discontinuity Condition/Filling, Ja
Groundwater Conditions, Jw
Stress Reduction Factor, SRF
The relation between grout-takes (kg/tunnel-m) and Q-value 58
ready 58

59. RMR based on five parameters: Uniaxial strength of the intact rock qu
Rock Mass Rating (RMR)
RMR based on five parameters:
Uniaxial strength of the intact rock qu
Rock Quality Designation RQD
Spacing of Discontinuities.
Condition of the Discontinuities, length, roughness.
Aperture width, infill, weathering.
Groundwater Conditions.
RMR = R1+R2+R3+R4+R5
Adjustment for joint orientation relative to construction.
9 ratings to add  RMRbasic = 100 maximum
ready

60. Geomechanics Systems (CSIR) [after Bieniawski, 1984, 1989]
Rock Mass Rating (RMR)
Geomechanics Systems (CSIR) [after Bieniawski, 1984, 1989]
ready

61. Geomechanics Systems (CSIR) [after Bieniawski, 1984, 1989]
Rock Mass Rating (RMR)
Geomechanics Systems (CSIR) [after Bieniawski, 1984, 1989]
ready

62. Relation between in situ modulus of deformation and RMR
Rock quality
0 - 20
Very poor
Poor
Fair
Good
Very good
ready

63. RMR Rock quality 0 - 20 Very poor 21 - 40 Poor 41 - 60 Fair 61 - 80
RMR vs Stand-up Time
RMR
RMR
Rock quality
0 - 20
Very poor
Poor
Fair
Good
Very good
100 hours
ready

64. Flow chart of the basic procedure for design of underground structures
RQ – required project goals
Flow chart of the basic
procedure
for design of underground
structures
SB – the system behaviour in actual tunnel (failure modes)
press
press
ready

65. SB – the system behaviour for Icelandic tunnel (failure modes)
ready

66. D&B Excavation Classes (Kárahnjúkar Hydropower Project)
Quantiy of support installed in the heading zone.
Rock face composition does not affect the excavation class.
Heading zone = 3 round lengths.
Class 1 = 50 mm shotcrete in crown and/or < 2 bolts/m.
Class 4 = Steel ribs & lagging with 150 mm of shotcrete from invert to invert.
D&B Excavation Classes (Kárahnjúkar Hydropower Project)
press
press
ready

67. Excavation Classes vs. Permanent Supporting System
(Kárahnjúkar Hydropower Project)
Excavation Classes vs. Permanent Supporting System
ready

68. THE END (of part 1)
French fishermen ships in Fáskruðsfjördur
ready

69. Thank You for Your attention!
ready

70. Welcome to www.najder.se
ready