By Shri Manoj Verman, President, Indian National Group of ISRM
President, International Commission on Hard Rock Excavation
Vice President, Indian Society of Engineering Geology
at 31st National Convention of Civil Engineering
organised by
Gujarat State Center, The Institution of Engineers (India)
at Ahmedabad
An introduction to Semiconductor and its types.pptx
Challenges of Tunneling-- A Peep Into The Exciting World of Tunnelling
1. Dr Manoj Verman
Tunnelling & Rock Engineering Consultant
CHALLENGES OF TUNNELLING
A PEEP INTO THE EXCITING WORLD OF TUNNELLING
CHALLENGES OF TUNNELLING
A PEEP INTO THE EXCITING WORLD OF TUNNELLING
2. CHALLENGES OF TUNNELLING
A PEEP INTO THE EXCITING WORLD OF TUNNELLING
Dr Manoj Verman
President, Indian National Group of ISRM
President, International Commission on Hard Rock Excavation
Vice President, Indian Society of Engineering Geology
5. Mverman
THE HIMALAYAS, THE ANDES & THE ALPS – THE MOST
DIFFICULT TUNNELLING MEDIA IN THE WORLD
Himalayas
Alps
Andes
6. Mverman
TUNNEL BEHAVIOUR
• Tunnel behaviour is influenced by:
Insitu and induced stress
Geological structure/jointing,
Rock mass strength, and
Groundwater conditions.
19. Mverman
BRITTLE CONDITION
Maximum boundary
stress / Uniaxial
Compressive strength
Spalling
description
smax/sc ≈ 0.9 Minor to
moderate
spalling
smax/sc ≈ 1.2 Severe spalling
occurs
smax/sc ≈ 1.6 Spalling takes the
form of
rockbursts in
hard brittle rock
21. Mverman
SQUEEZING CONDITION
• Squeezing conditions in weak rock
masses – failure zone around a tunnel
generally requires the installation of
passive support (i.e. concrete lining)
33. Faults & rock strength
& … the two ends of the rock competence scale
Weak Ground –
Squeezing
Competent Ground – Bursting
Graphite Schist
Quartzite
34. Mverman
FAULTS
• Faults are fractures in crustal strata along
which rocks have been displaced
• The amount of displacement may vary
from only a few tens of millimetres to
several hundred kilometres
• In many faults, the fracture is a clean
break; in others, the displacement is not
restricted to a simple fracture, but is
developed throughout a fault zone
Fault in strata of the Limestone Group, Lower
Carboniferous, near Howick, Northumberland, England
35. Mverman
KALIASAUR – THE FAMOUS LANDSLIDE
(ON ROAD FROM SRINAGAR TO RUDRAPRAYAG, UTTARAKHAND
Kaliasaur - Crushed and broken quartzite rock mass associated with the ENE-WSW sub-
vertical fault system. Rock mass appears tectonically disturbed and completely broken.
38. Mverman
HIMALAYAN FAULT ZONES
• In general, the fault zones consist of
a highly deformed fault core (core
zone) and of a surrounding and
very fractured “damage zone”
• In these fault zones, water
circulation can also trigger
weathering processes due highly
fractured rocks, generating gouge
material (clayey sub-products)
• The expected thickness of the core
zone generally varies from 1 to
10m.
39. Mverman
“TOOTHPASTE” FAULT
(MYLONITIZED & GRANULATED
Mud flow Conditions
50m back from face
100 m mudflow along
tunnel
Severe Disruption to
already installed
support
Conditions much easier
WITHOUT WATER
47. 47
Wedge instability Rockfall
Support class A B C1
Main design action Mitigations
Confinement of rock wedges Bolts and fibre-reinforced shotcrete
Control of water pressure/inflow Drainages in advance
Long term stability Concrete final lining
Examples of Support Types
48. 48
Rockfall/caving Severe caving (faults,..)
Support class C2 F
Main design action Mitigations
Increase self-supporting
capacity
Forepoling umbrella pipes
Stabilisation of tunnel face (F) Pre-consolidation by fibreglass elements
Control of water
pressure/inflow
Drainages in advance
Radial reinforce and
confinament
Lattice girders/Steel ribs, fbr shotcrete,
bolts
Long term stability Concrete final lining with invert (F)
Examples of Support Types
49. Mverman
Hazard Wedge instability
Description Gravitational fall of rock blocks isolated by the
discontinuity network (weight force>shear
strength)
Instability Generally sudden, short term instability
Evolution Frequently an equilibrium condition is reached,
but this may be after fall of other wedges
Mitigation Preventive bolting, reduction of round length,..
V-Unstable wedges (2/6)Unstable Wedges
53. Mverman
Hazard Caving
Description Gravitational fall of portions of fractured rock
mass or weakly cohesive soils, eventually
alimented by the presence of water
Instability Generally sudden, short term instability
Evolution The complete collapse of the face may be
reached, with concurrent caving of tunnel crown
contour (chimney formation)
Mitigation Drainages, preconsolidation of the core,
prearmature/preconfinement of contour
excavation..
Caving
55. Technical solution for face
instability:
GALLERIE MO
Titolo :
PROGET
ANA
³
d
- Drainages (d)
fb
- cemented fibreglass (fb) u
u
- pipe umbrella arch (u)
Caving
56. Collapse of the face intercepting suddenly unforeseen water bearing, very fractured
and weathered rock mass (H=30m)
Vispa tunnel (Italy)
Caving
57. Technical solution 1 (>silty sands):
Menaggio tunnel (Italy)
VI-Caving (10/15)
- Drainages (d)
d
- Protective canopy:
jg+ pipe umbrella (u)
jg+u
- Jet grouting (jg) at
the face
jg
58. Menaggio tunnel (Italy)
s
Technical solution 2 (>mix
condition):
VI-Caving (11/15)
- Drainages (d)
d
- Protective canopy: jg+
pipe umbrella (u)
jg+u
jg+u
- face reinforcement by
jg/ cemented fibreglass
fb (lower section in
silty clay)
jg/fb