monitoring / shortŒterm predictionmonitoring /...

GruppeGeotechnikGraz ZT GMBH

! Verify design assumptions

! Together with updated geotechnical model allow short term prediction

! Provide input for final design and optimization of excavationand support on site

! Prediction of final displacements

! Control stability

! Data collection for future developments (expert systems)

TARGETS

MONITORING / SHORT�TERM PREDICTIONMONITORING / SHORT�TERM PREDICTION

EMedley

Text Box

FROM AEG SHORT COURSE " Tunnels Through Fault Rocks and Tectonic Melanges: A Short Course for Engineering Geologists and Geotechnical Engineers", Oakland, California; June 1, 2002; Instructors: Prof. Gunter Riedmueller and Prof. Wulf Schubert, Technical University of Graz, Austria and Gruppe Geotechnik Graz COPYRIGHT OF 3G - Gruppe Geotechnik Graz www.3-g.at REPRODUCED AND PROVIDED WITH THE PERMISSION OF AEG and 3G CONTACT: Dr. Alfred Fasching, CEO and Managing Director: [email protected]


! Absolute displacements of tunnel wall with electronic total station

! Relative displacement measurements with precision measuring tape, extensometers, inclinometers

! strains

METHODS



Tape convergence meter Multiple extensometers

Levelling points

METHODS



ABSOLUTE DISPLACEMENTS



! Displacements influenced by:

� Rock mass properties� Heterogeneity� Tunnel size� Primary stresses� Excavation sequence� Excavation rate� Support

INFLUENCING FACTORS



0

10

20

30

40

50

60

0 5 10 15 20 25 30 35 40days

settl

emen

t (m

m)

0

30

60

90

120

150

180

adva

nce

(m)

TIME � DISPLACEMENTcontinuous advance



0

10

20

30

40

50

60

0 5 10 15 20 25 30 35 40days

settl

emen

t (m

m)

0

30

60

90

120

150

180

adva

nce

(m)

TIME � DISPLACEMENTdiscontinous advance



0

10

20

30

40

50

60

0 5 10 15 20 25 30 35 40days

settl

emen

t (m

m)

0

30

60

90

120

150

180

adva

nce

(m)

TIME � DISPLACEMENTcomparison



PREDICTION OF DISPLACEMENTS



predicted displacements

PREDICTION OF DISPLACEMENTS



with top heading invert

without top heading invert


DIFFERENT SUPPORT



COMPARISON PREDICTION - REALITY


failure of top heading invert


DEVIATIONS FROM PREDICTION


collapse


DEVIATIONS FROM PREDICTION



Gräbern Tunnel, Austria

ROOF SETTLEMENTS, DEFLECTION CURVES




DISPLACEMENT VECTORS



DISPLACEMENT RATIO


DISPLACEMENT VECTOR ORIENTATION



HETEROGENEITY � VECTOR ORIENTATION



SETTLEMENT & VECTOR ORIENTATION TRENDS



DEFLECTION CURVE & VECTOR ORIENTATION TRENDS




DISPLACEMENT VECTORS


Inntal Tunnel, Austria


SPATIAL DISPLACEMENT VECTOR



VECTOR ORIENTATION - TREND


Hinterberg Fault Zone, Galgenberg Tunnel, Austria


lateral creepingof fault material

excavation

"arch" effect

Fault Zone

ARCH EFFECT




VISUALIZATION OF MONITORED DATA




! Mixed face conditions require different excavation methods on the same section

! Strong variation of rock mass quality! Stress redistribution and deformations extremely influenced by

arrangement of blocks and matrix! Prediction of displacements and lining utilization extremely difficult! Danger of brittle failures in blocks! Difficulty to determine proper support

BIMROCK EFFECTSBIMROCK EFFECTS


-0,45

-0,40

-0,35

-0,30

-0,25

-0,20

40 50 60 70 80 90 100

110

120

130

140

150

160

170

180

∆r

520 40

75

! Displacements depend on the length of the weak zone between two stiff blocks

DISPLACEMENTS IN MATRIX IN RELATION TO BLOCK DISTANCE PROBLEMS



! Final displacements influenced by zone length and stiffness contrast

-1,10

-1,00

-0,90

-0,80

-0,70

-0,60

-0,50

-0,40

-0,30

-0,20

40 50 60 70 80 90 100

110

120

130

140

150

160

170

180

E1/E2 = 1,5

E1/E2 = 2,0

E1/E2 = 4,0

DISPLACEMENTS



1,80

1,90

2,00

2,10

2,20

2,30

2,40

2,50

2,60

2,70

40,0

50,0

60,0

70,0

80,0

90,0

100,0

110,0

120,0

130,0

140,0

150,0

160,0

170,0

180,0

F 1,5 / Var 8

F 2,0 / Var 8

F 4,0 / Var 8

σ1/p1

! Stress concentation in blocks depend on stiffness contrast and distance between blocks

STRESS DISTRIBUTION



STRESS CONCENTRATIONS



chainage [D]

verc

tor o

rient

atio

n [°

]

advance

settl

emen

t [m

]st

ress

/

σ

σZ

V,PR

IM[-]

chainage [D]

chainage [D]

STIFF STIFFSOFT

VEC

TOR

OR

IEN

TATI

ON

TREN

D +

1/2

DFI

NA

L SE

TTLE

MEN

TSFI

NA

L ST

RES

SES

NO

RM

ALIS

ED

σ σZ V,PRIM / [-]

MODEL1.1

2/3 E stiff

1/2 E stiff

1/4 E stiff

�normal�

�normal�Relative stress increasein stiff material

Relative stress decreasein soft material

Trough shaped displacement

Change of displacementvector orientation near transition

STIFF-SOFT-STIFF



! Stress concentrations can cause brittle failure in stiff blocks ! Resulting 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

BLOCK REINFORCEMENT



CASE STUDIES

Location Map

Tunnel Spital, Austria



! Twin 2,2 km long freeway tunnels in the Semmering region, eastern Austria

! Alignment along a major fault zone

! Excavation area 70 � 90 m2

! Underpassing of a railway line and built up area

! Maximum overburden 80 m

Project data

CASE STUDIES




Geological overview

CASE STUDIES




Nord tube: 1870-2000m

South tube: 1700-1800m

Geological overview

CASE STUDIES





Heterogeneity - Displacements

CASE STUDIES



Block

BIMROCK EFFECTSBIMROCK EFFECTSCASE STUDIES


Block effect on displacementsettlement crown / top heading


1773

1777

1779 1790

1788

1785



Cross sections




Bench excavation


! During bench excavation the block fails, leading to additional 60 mm of settlement



Failure of block




Final displacements & displacement vector orientation trend


cracks in the shotcrete on the southern sidewall

DAMAGESCASE STUDIES



GruppeGeotechnikGraz ZT GMBHGalgenberg Tunnel, Austria

CASE STUDIES

Project Data

Single tube double track railway tunnel, length 5142 m, maximum overburden 260 m. Design from 1990 to 1992. The construction (three headings) started in June 1993 and was completed in April 1996.

Tasks

Geological � geotechnical site investigation from the feasibility study to the tender design. Consultant services during construction

Geology

Paleozoic graphitic phyllite, greenschist and marble as well as Permo-Triassic quartzite, quartzphyllite and agglomeratewere subjected to intense Alpine thrusting and Tertiary strike-slip faulting


GruppeGeotechnikGraz ZT GMBHGalgenberg Tunnel, Austria

CASE STUDIES

Collapse

A collapse with fatal accident happened on July 1994 at station 1330 m. Eight meters of heavily supported tunnel section collapsed at the face.A miner, including excavation equipment, was buried under the collapsed rock mass.Redesign and maintenance work lasted for two months. The excavation was resumed in October 1994.



Collapse caused by brittle failure of stiff rock outside of excavation

Collapse

Galgenberg Tunnel, Austria

CASE STUDIES



HINTERBERG FAULT ZONEPrediction


CASE STUDIES



30

20

10

0

-10

-20

(L/S

)[°]

Plan view

Longitudinal section

HINTERBERG FAULT ZONEActual Situation


CASE STUDIES



HABERL FAULT - IMPROVED PROCEDURE

Modification of excavtion and support � reduction of top heading heigth, yielding elements, regroutable rock bolts


CASE STUDIES



Heterogeneity showing in strong variation of the vector orientation trend

-40

1800 1850 1900 1950 2000 2050

30

20

10

0

-10

-20

-30

-50

∆α

[°]

HABERL FAULT ZONE


CASE STUDIES



! The complex spatial distribution of rock masses with different stiffness and strength makes prediction of behaviour difficult

! High displacments as well as differences in displacements can lead to severe damage of the (stiff) lining; thus flexible linings are required where bigger displacements are expected, and preferable even in shallow tunnels

! The analysis of the diplacement vector orientations can support the prediction of the location and distribution of blocks

CONCLUSION


monitoring / shortŒterm predictionmonitoring /...

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