Lecture 4
Tunneling Through Fault Zones and
Melanges
BIMROCKS SHORT COURSE
Dr. Edmund Medley
Consulting Geological Engineer, Belmont, California, USA
[email protected]
Geological Engineering Department, Haceteppe Univ, Ankara
June 22 and 23, 2004
Much of this lecture is
possible thanks to the use
of slides and photographs
permitted by:
Gruppe Geotechnik Graz,
Austria
Prof. Dick Goodman
Copyright: Dr. Edmund Medley, PE CEG
Consulting Geological Engineer
[email protected]
2
BIG CONCLUSION 1:
Remember this picture!!!
Matrix
Blocks, inclusions,
lenses, etc
Proposed
Tunnel
Scale: 1:??????
Matrix
Actual Distribution of Blocks
Medley, 2000
BIG CONCLUSION 2:
Remember this picture as well!!!
Matrix
Proposed Tunnel
Matrix
Apparent Distribution of Blocks
Willis, 2000
Tunneling failures can occur in relatively coherent rock-masses
Photo: courtesy
Prof. R. Goodman
Copyright: Dr. Edmund Medley, PE CEG
Consulting Geological Engineer
[email protected]
5
Some
SomeRock
RockMass
MassBEHAVIOUR
BEHAVIOURTYPES
TYPES
Copyright: Dr. Edmund Medley, PE CEG
Consulting Geological Engineer
[email protected]
6
Tunneling
Tunnelingin
infault
faultrocks
rocksand
andmelanges
melangescan
canresult
resultin
in failures
failures
Collapsed Tunnel M2, Egnatia Motorway, Greece
Copyright: Dr. Edmund Medley, PE CEG
Consulting Geological Engineer
[email protected]
7
Tunnel
TunnelCollapse
Collapsein
inunexpected
unexpectedbimrock
bimrock
Galgenberg Tunnel, Austria
Copyright: Dr. Edmund Medley, PE CEG
Consulting Geological Engineer
[email protected]
8
Example
Study
of
Hazard
Hepp
Kavsak
(Turkey)
ExampleCase
Case
Study
ofGeotechnical
Geotechnical
Hazard
Hepp
Kavsak
(Turkey)
Assessment
Assessment
Project Data
Upgrading of the river for energy production.
• Headrace tunnel (length 9km, diameter 9,0m
• Power house
Tasks
Geotechnical hazard assessment and optimization of design
prior to construction
Copyright: Dr. Edmund Medley, PE CEG
Consulting Geological Engineer
[email protected]
9
Geotechnical
GeotechnicalLongitudinal
LongitudinalSection
Sectionfor
forthe
theTender
TenderDesign
Design
“faulted”
Copyright: Dr. Edmund Medley, PE CEG
Consulting Geological Engineer
[email protected]
10
Site
Sitemapping
mappingin
infaulted
faultedrocks
rocks
Copyright: Dr. Edmund Medley, PE CEG
Consulting Geological Engineer
[email protected]
11
Site
Sitemapping
mapping
Geotechnical Hazard Assessment
Copyright: Dr. Edmund Medley, PE CEG
Consulting Geological Engineer
[email protected]
12
Site
Sitemapping
mappingof
ofgeological
geologicalstructures
structures
Copyright: Dr. Edmund Medley, PE CEG
Consulting Geological Engineer
[email protected]
13
Site
Sitemapping
mappingof
ofbimrock...
bimrock...
Copyright: Dr. Edmund Medley, PE CEG
Consulting Geological Engineer
[email protected]
14
Revised
Revised Geotechnical
Geotechnical Longitudinal
Longitudinal Section
Section
Fault zones with bimrocks
Copyright: Dr. Edmund Medley, PE CEG
Consulting Geological Engineer
[email protected]
15
Geotechnical
GeotechnicalLongitudinal
LongitudinalSection
Sectionfor
forthe
theTender
TenderDesign
Design
“faulted”
Copyright: Dr. Edmund Medley, PE CEG
Consulting Geological Engineer
[email protected]
16
BIMROCK
BIMROCKEFFECTS
EFFECTSin
inTUNNELS
TUNNELS
¾ Mixed face conditions require different
excavation methods on the same section
¾ Strong variation of rock mass quality
¾ Stress redistribution and deformations
extremely influenced by arrangement of
blocks and matrix
¾ Prediction of displacements and lining
utilization extremely difficult
¾ Danger of brittle failures in blocks
¾ Difficulty of determination of proper support
Copyright: Dr. Edmund Medley, PE CEG
Consulting Geological Engineer
[email protected]
17
BIMROCK
BIMROCKEFFECTS
EFFECTS
PROBLEMS of
DISPLACEMENTS IN MATRIX IN RELATION TO BLOCK DISTANCE
¾Displacements depend on the length of the
180
170
160
150
140
130
120
110
100
90
80
70
60
50
40
weak zone between two stiff blocks
-0,20
-0,25
-0,30
5
-0,35
Δr
length of
weak zone
20
40 m
75 m
-0,40
Δr
-0,45
Copyright: Dr. Edmund Medley, PE CEG
Consulting Geological Engineer
[email protected]
18
BIMROCK
BIMROCKEFFECTS
EFFECTS
DISPLACEMENTS
¾Final displacements influenced by zone length and
180
170
160
150
140
130
120
110
100
90
80
70
60
50
40
stiffness contrast between blocks and matrix
-0,20
-0,30
-0,40
E1/E2 = 1,5
-0,50
-0,60
-0,70
E1/E2 = 2,0
E1/E2 = 4,0
-0,80
-0,90
-1,00
-1,10
Copyright: Dr. Edmund Medley, PE CEG
Consulting Geological Engineer
[email protected]
19
BIMROCK
BIMROCKEFFECTS
EFFECTS
180,0
170,0
160,0
150,0
140,0
130,0
120,0
110,0
90,0
80,0
70,0
60,0
50,0
40,0
σ1/p1
100,0
STRESS DISTRIBUTION
¾Stress concentration in blocks depend on
stiffness contrast and distance between blocks
2,70
2,60
2,50
2,40
2,30
2,20
2,10
2,00
1,90
F 1,5 / Var 8
F 2,0 / Var 8
F 4,0 / Var 8
1,80
Copyright: Dr. Edmund Medley, PE CEG
Consulting Geological Engineer
[email protected]
20
BIMROCK
BIMROCKEFFECTS
EFFECTS
STRESS CONCENTRATIONS
Copyright: Dr. Edmund Medley, PE CEG
Consulting Geological Engineer
[email protected]
21
BIMROCK
BIMROCKEFFECTS
EFFECTS
advance
STIFF
stress σZ / σV,PRIM [-]
σZ / σV,PRIM [-]
NORMALISED
FINAL STRESSES
MODEL
1.1
SOFT
STIFF
STIFF-SOFT-STIFF
Relative stress increase
in stiff material
“normal”
2/3 E stiff
1/2 E stiff
1/4 E stiff
Relative stress decrease
in soft material
settlement [m]
FINAL SETTLEMENTS
chainage [D]
Trough shaped displacement
verctor orientation [°]
TREND +1/2 D
VECTOR ORIENTATION
chainage [D]
“normal”
Change of displacement
vector orientation near
transition
Copyright: Dr. Edmund Medley, PEchainage
CEG[D] Consulting Geological Engineer
[email protected]
22
BIMROCK
BIMROCKEFFECTS
EFFECTS
BLOCK REINFORCEMENT
¾Stress concentrations can cause brittle failure in stiff
blocks
¾Resulting stress redistribution leads to additional
displacements in the matrix material
• Knowledge of the spatial distribution of blocks and matrix
•
•
essential to properly estimate stress situation
Short term prediction and prediction of displacements
extremely important
Support / reinforcement of blocks necessary to avoid brittle
failure and long term stress redistribution, frequently
mistaken for creeping
Copyright: Dr. Edmund Medley, PE CEG
Consulting Geological Engineer
[email protected]
23
BIMROCK
BIMROCKEFFECTS
EFFECTS
CASE STUDIES
Location Map
Tunnel Spital, Austria
Copyright: Dr. Edmund Medley, PE CEG
Consulting Geological Engineer
[email protected]
24
BIMROCK
BIMROCK EFFECTS:
EFFECTS: Case
Case Study
Study
Project data : Tunnel Spital, Austria
¾ Twin 2,2 km long freeway tunnels in the
Semmering region, eastern Austria
¾ Alignment along a major fault zone
¾ Excavation area 70 – 90 m2
¾ Underpass of a railway line and built up area
¾ average overburden 30 m, maximum 80 m
Copyright: Dr. Edmund Medley, PE CEG
Consulting Geological Engineer
[email protected]
25
BIMROCK
BIMROCKEFFECTS
EFFECTSCASE
CASESTUDY
STUDY
Tunnel Spital, Austria
Copyright: Dr. Edmund Medley, PE CEG
Geological overview
Consulting Geological Engineer
[email protected]
26
BIMROCK
BIMROCKEFFECTS
EFFECTSCASE
CASESTUDY
STUDY
Geological sections at tunnel faces at various tunnel locations
1773
1785
1777
1788
1779
1790
Tunnel Spital, Austria
Copyright: Dr. Edmund Medley, PE CEG
Consulting Geological Engineer
[email protected]
27
BIMROCK
BIMROCKEFFECTS
EFFECTSCASY
CASYSTUDY
STUDY
Geological overview
Nord tube: 1870-2000m
South tube: 1700-1800m
Copyright: Dr. Edmund Medley, PE CEG
Consulting Geological Engineer
[email protected]
28
BIMROCK
BIMROCKEFFECTS
EFFECTSCase
Casestudy
study
Heterogeneity - Displacements
Tunnel Spital, Austria
Copyright: Dr. Edmund Medley, PE CEG
Consulting Geological Engineer
[email protected]
29
BIMROCK
BIMROCKEFFECTS
EFFECTSCASE
CASESTUDY
STUDY
Block effect on displacement
settlement crown / top heading
Block
Tunnel Spital, Austria
Copyright: Dr. Edmund Medley, PE CEG
Consulting Geological Engineer
[email protected]
30
BIMROCK
BIMROCKEFFECTS:
EFFECTS:COLLAPSE
COLLAPSEat
atGALGENBERG
GALGENBERGTUNNEL,
TUNNEL,AUSTRIA
AUSTRIA
A fatal collapse July 1994 at station 1330 m.
Eight meters of heavily supported tunnel section collapsed at the face.
A miner, and equipment was buried
Redesign and maintenance work lasted for two months.
Collapse caused by brittle failure of stiff rock
outside of excavation
Copyright: Dr. Edmund Medley, PE CEG
Consulting Geological Engineer
[email protected]
31
BIG CONCLUSION 1:
Remember this picture!!!
Matrix
Blocks, inclusions,
lenses, etc
Proposed
Tunnel
Scale: 1:??????
Matrix
Actual Distribution of Blocks
Medley, 2000
BIG CONCLUSION 2:
Remember this picture as well!!!
Matrix
Proposed Tunnel
Matrix
Apparent Distribution of Blocks
Willis, 2000
Copyright: Dr. Edmund Medley, PE CEG
Consulting Geological Engineer
[email protected]
34
ex•po•nent
(ik-spo’nent) n.
1. One who expounds or interprets.