The Croatian experience in the use of the interactive design method

Transcription

1 The Croatian experience in the use of the interactive design method Antun Szavits-Nossan Meho Saša Kovačević University of Zagreb, Croatia 10 May 2005 IREX Symposium: The interactive design mnethod, Paris,

2 Content Incentives Monitoring instruments Five case histories New developments Final remark 10 May 2005 IREX Symposium: The interactive design mnethod, Paris,

3 Incentives Large infrastructure projects Ground conditions that defy standard design methods (soft, fissured, jointed and heterogeneous rocks/soils) Risk management The Croatian motorway project 10 May 2005 IREX Symposium: The interactive design mnethod, Paris,

4 Monitoring instruments Surveying Borehole measurements: Inclinometers Sliding micrometers Piezometers Anchor load cells Total pressure cells Clinometers, etc. Sliding micrometer, Solexperts, Switzerland 10 May 2005 IREX Symposium: The interactive design mnethod, Paris,

5 Case history I St Mark s tunnel 10 May 2005 IREX Symposium: The interactive design mnethod, Paris,

6 St Mark s tunnel (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 LONGITUDINAL SECTION A-A Shotcrete C25, 30cm +two reinforcement meshes Q Steel lattice girder PS 95/20/30 CROSS-SECTION B-B Detail 2 Kalota B B ±0.00 Detail 1 ± Pipe roof A Face protection core 6 Protective pipe dia.114.3mm, l=15m Face protection Shotcrete 10cm (+1 reinforcement mesh Q188 if required) Face protection Shotcrete 10cm (+1 renforcement mesh Q188 if required) Shotcrete C25, 30cm, two reinforcement meshes Q283, steel lattice girder PS 95/20/30 Elephant foot if required IBO anchors l=6m Invert A 10 May 2005 IREX Symposium: The interactive design mnethod, Paris,

7 St Mark s tunnel (3) Inclinometer and sliding deformeter layout settlement 1 cm mm depth (m) 10 May 2005 IREX Symposium: The interactive design mnethod, Paris,

8 St Mark s tunnel (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) 10 May 2005 IREX Symposium: The interactive design mnethod, Paris,

9 Case history II: Zagrad excavation 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 Elevation (m) VERTICAL INCLINOMETER - DEFORMETER POMERIO ST. SELF-DRILLING ROCKBOLTS L=16.0 m Horizontal deformeter L=16.0 m POMERIO ST. No.19 SELF-DRILLING ROCKBOLTS SELF-DRILLING ROCKBOLTS L=16.0 m L=12.0 m Horizontal distance (m) May 2005 IREX Symposium: The interactive design mnethod, Paris,

10 Zagrad excavation (2) Observational method: Initial design limits of behaviour (strain distribution, anchor loads) Monitoring: inclinometer, sliding deformeter, load cells on anchors; benchmark survey Contingency actions: anchor prestressing, additional anchors displacement (mm) distance from excavation face (m) 10 May 2005 IREX Symposium: The interactive design mnethod, Paris,

11 Case history III: Kaufland excavation Excavation: 17 m deep, adjacent 8 storey apartment building Geology: jointed and layered limestone partially degraded 82 Design: staged excavation, 76 reinforced shotcrete, rock bolts 0 Elevation (m) Slope line before excavationh terrace level foundation level V CRNCIC ST BUILDING SELF-DRILLING ROCKBOLTS L=12.00 m SELF-DRILLING ROCKBOLTS L=9.00 m SELF-DRILLING ROCKBOLTS L=6.00 m V - vertical inclinometer - deformeter L=18.00 m H - horizontal deformeter L=15.00 m Horizontal distance (m) May 2005 IREX Symposium: The interactive design mnethod, Paris,

12 Kaufland excavation (2) Observational method: Initial design Monitoring: inclinometer, horizontal sliding deformeter Contingency actions due to non stabilizing deformations above the excavation section: shortening of excavation section additional layer of shotcrete 10 May 2005 IREX Symposium: The interactive design mnethod, Paris,

13 Case history IV: Lenac excavation Excavation 35 m to 55 m deep Geology Weathered limestone, breccia, flysh Design Staged excavation, multilayered reinforced shotcrete, rock bolts ROCKBOLTS L=9.00 m SELF-DRILLING ROCKBOLTS L=12.00 m ROCKBOLTS L=6.00 m VERTICAL INCLINOMETER - DEFORMETER L=40.0 m Horizontal deformeter L=15.00 m Horizontal distance (m) Elevation (m) 10 May 2005 IREX Symposium: The interactive design mnethod, Paris,

14 Lenac 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 10 May 2005 IREX Symposium: The interactive design mnethod, Paris,

15 Case history V: WTC excavation Excavation 15 m deep Geology Weathered limestone, breccia, flysh Design Staged excavation, reinforced shotcrete, rock bolts, prestressed anchors Elevation (m) H V ROCKBOLTS L=5.00 m SELF-DRILLING ROCKBOLTS L=9.00 m SELF-DRILLING ROCKBOLTS L=6.00 m V - vertical inclinometer - deformeter L=16.00 m H - horizontal deformeter L=15.00 m Horizontal distance (m) 10 May 2005 IREX Symposium: The interactive design mnethod, Paris,

16 WTC excavation (2) Observational method: Initial design limits of behaviour (strain distribution, displacements) Monitoring: inclinometer, sliding deformeter Contingency actions: additional shotcrete layer, additional anchors 10 May 2005 IREX Symposium: The interactive design mnethod, Paris,

17 New developments Initial research in acoustic emission as a means to detect rock bolt overstressing Tensile force (kn) Number of counts/tensile force (n/kn) 10 May 2005 IREX Symposium: The interactive design mnethod, Paris,

18 Final remark on the initial design for 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). Optimal probability for initial design, p Relative cost of contingency actions, k Muir Wood (2000) Peck (1969) 10 May 2005 IREX Symposium: The interactive design mnethod, Paris,

19 References 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), Powderham, A. J. (1994). An overview of the observational method: development in cut and cover bored tunnelling projects. Géotechnique, 19(2), May 2005 IREX Symposium: The interactive design mnethod, Paris,

20 Thank you for your attention 10 May 2005 IREX Symposium: The interactive design mnethod, Paris,