the croatian experience in the use of the interactive...

10 May 200510 May 2005 11IREX Symposium: The interactive design mnethod, Paris, 2005IREX Symposium: The interactive design mnethod, Paris, 2005

The Croatian experienceThe Croatian experience ininthe use of the interactive the use of the interactive

design methoddesign method

Antun SzavitsAntun Szavits--NossanNossanMeho Saša KovačevićMeho Saša KovačevićUniversity of Zagreb, CroatiaUniversity of Zagreb, Croatia

10 May 200510 May 2005 IREX Symposium: The interactive design mnethod, Paris, 2005IREX Symposium: The interactive design mnethod, Paris, 2005 22

ContentContent

• Incentives• Monitoring instruments• Five case histories• New developments• Final remark


IncentiveIncentives s The Croatian motorway project

• Large infrastructure projects

• Ground conditionsthat defy standard design methods (soft,fissured, jointed and heterogeneousrocks/soils)

• Risk management


Monitoring instrumentsMonitoring instruments

• Surveying• Borehole

measurements:– Inclinometers– Sliding micrometers– Piezometers

• Anchor load cells• Total pressure cells• Clinometers, etc.

Sliding micrometer,Solexperts, Switzerland


Case history Case history II –– St Mark’s tunnelSt Mark’s tunnel


St Mark’s tunnel St Mark’s tunnel (2)(2)• Tunnel:

– < 22 m overburden, length 264 m, two tubes

• Geology:– from 0 m – 20 m: layers of mixed

clay, sand, silt and sandstone lumps

– > 20 m: dolomites, irregularly disintegrated

• Requirements:– limit surface settlements

(preservation of cemetery)• Design:

– Pipe roof, short excavation segments, immediate closure of the support ring, reinforced shotcrete, self-boring anchors

+8.00

+2.80

±0.00

-0.20-1.95

Invert

+2.50

Kalota

Face protection core

Face protectionShotcrete 10cm(+1 renforcement mesh Q188 if required)

Elephant foot if required

IBO anchors l=6m4980

16000

9530

30

30

30 30

CROSS-SECTION B-B

A

A

Detail 2

12.0012.00

7.18

Face protectionShotcrete 10cm(+1 reinforcement mesh Q188 if required)

7

531

642

LONGITUDINAL SECTION A-A

Shotcrete C25, 30cm+two reinforcement meshes Q283

Detail 1Protective pipe dia.114.3mm, l=15m

8.00

Steel lattice girder PS 95/20/30

15

3.91°

±0.00

-1.95

-0.20

+2.50

+8.00

B

B

Pipe roof100°-114°

Shotcrete C25, 30cm,two reinforcement meshes Q283,steel lattice girder PS 95/20/30


St Mark’s tunnelSt Mark’s tunnel (3)(3)Inclinometer and sliding deformeter layout

settlement 1 cm 0 4-4 8-8mm0

depth (m)

1 2 3 4 5 6 7


St Mark’s tunnelSt Mark’s tunnel (4)(4)

• Observational method:– establishing acceptable limits of behaviour

(acceptable surface settlements)– initial design– monitoring surface settlements and strains

along boreholes; pressure cells; measuring anchors

– applying contingency actions (adjusted excavation method; added additional rock bolts)


Case history Case history IIII:: ZagradZagrad excavationexcavation

• Excavation– Vertical cut 14 m – 20 m

deep– Adjacent 5 storey old

brick apartment house • Geology

– Flysh deposits overlain by 5 m of irregular fill

• Design– Staged excavation, RC

box girder, rock bolts

POMERIO ST. No.19INCLINOMETER -VERTICAL

30

0L=16.0 m

50Horizontal distance (m)

1510 2520

L=12.0 m

Ele

vatio

n (m

)

15 Horizontal deformeterL=16.0 m

5

10

L=16.0 m20

25

DEFORMETER

POMERIO ST.

3530

SELF-DRILLING ROCKBOLTS

SELF-DRILLING ROCKBOLTS SELF-DRILLING ROCKBOLTS


ZagradZagrad excavation (2)excavation (2)• Observational

method:– Initial design → limits

of behaviour (strain distribution, anchor loads)

– Monitoring: inclinometer, slidingdeformeter, load cells on anchors; benchmark survey

– Contingency actions: anchor prestressing, additional anchors

0

1

1

2

2

3

3

4

0510152025distance from excavation face (m)

disp

lace

men

t (m

m)


Case history Case history IIIIII:: KauflandKaufland excavationexcavation

• Excavation: 17 m deep, adjacent 8 storey apartment building

• Geology: jointed and layered limestone partially degraded

• Design: staged excavation, reinforcedshotcrete, rock bolts 0

68

74

70

72

76

80

78

82

84

86

90

88

92

V - vertical inclinometer - deformeter L=18.00 mH - horizontal deformeter L=15.00 m

SELF-DRILLING ROCKBOLTSL=6.00 m

+75.30 terrace level

+73.30 foundation level

10 20 30

H

V

40



L=12.00 m

L=9.00 m

+84.50

CRNCIC ST.

Slope linebefore excavation

BUILDING

Horizontal distance (m)

Ele

vatio

n (m

)


KauflandKaufland excavation (2)excavation (2)

• Observational method:– Initial design– Monitoring: inclinometer,

horizontal slidingdeformeter

– Contingency actions due to non stabilizing deformations above the excavation section:

• shortening of excavation section

• additional layer ofshotcrete


Case history IV:Case history IV: LenacLenac excavationexcavation

• Excavation– 35 m to 55 m deep

• Geology– Weathered limestone,

breccia, flysh• Design

– Staged excavation,multilayered reinforcedshotcrete, rock bolts

Horizontal deformeterL=15.00 m

DEFORMETER L=40.0 m

25 20 10 5 040 35 30Horizontal distance (m)

Elev

atio

n (m

)

SELF-DRILLING

L=12.00 m

ROCKBOLTSL=9.00 m

ROCKBOLTSL=6.00 m

3540

3025

01 0

205

45

ROCKBOLTS

VERTICAL INCLINOMETER -


LenacLenac excavation (2)excavation (2)

• Observational method:– Initial design → limits of

behaviour (strain distribution, anchor loads)

– Monitoring: inclinometer, sliding deformeter

– Contingency actions:prestressed anchor, additional anchors, shortening of excavation sections


Case history V: WTC excavationCase history V: WTC excavation

• Excavation– 15 m deep

• Geology– Weathered limestone,

breccia, flysh• Design

– Staged excavation, reinforced shotcrete, rock bolts, prestressedanchors

45

3735

4139

43

47

5149

5553

0 10 20 30

V

H

V - vertical inclinometer - deformeter L=16.00 mH - horizontal deformeter L=15.00 m

ROCKBOLTSL=9.00 m

ROCKBOLTSL=6.00 m

ROCKBOLTSL=5.00 m

Elev

atio

n (m

)

Horizontal distance (m)

SELF-DRILLING

SELF-DRILLING


WTC excavation (2)WTC excavation (2)• Observational method:

– Initial design → limits of behaviour (strain distribution, displacements)

– Monitoring: inclinometer, sliding deformeter

– Contingency actions: additional shotcretelayer, additional anchors


New developmentsNew developments

• Initial research in acoustic emission as a means to detect rock bolt overstressing

0.00

20.00

40.00

60.00

80.00

100.00

120.00

0 20000 40000 60000 80000 100000 120000 140000

Number of counts/tensile force (n/kN)

Tens

ilefo

rce

(kN

)

1

4

7

10

13

16

19

22

25

28

31

34

37

40

43

46


Final remark on the initial design Final remark on the initial design for the observational methodfor the observational method

• Peck, R. B. (1969): Establish design based on a working hypothesis of behaviour anticipated under the most probable conditions(p = 0.5);

• Powderham, A. J. (1994): A moderately conservative initial design based on more probable conditions (p > 0.5);

• Muir Wood, A. (2000): A conservative initial design for tunnels based on a simplified economical analysis (usually p > 0.5) .

1 2 3Relative cost of contingency actions, k

0.0

0.5

1.0

Opt

imal

pro

babi

lity

for i

nitia

l des

ign,

p

Peck (1969)

Muir Wood (2000)


ReferencesReferences

Muir Wood, A. (2000). Tunnelling: Management by design. E & FN Spon, London.

Peck, R. B. (1969). Advantages and limitations of the Observational Method in applied soil mechanics. Géotechnique, 44 (4), 619-636.

Powderham, A. J. (1994). An overview of the observational method: development in cut and cover bored tunnelling projects. Géotechnique,19(2),171-187.


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