Lessons learnt from constructing the FE tunnel incl. some monitoring results

Transcription

1 LUCOEX conference Oskarshamn, Sweden 3 rd of June 2015, Session 3 Lessons learnt from constructing the FE tunnel incl. some monitoring results Herwig R. Müller, Sven Köhler, Tobias Vogt

2 concrete plug (5m)

3 Geological overview Giger et al. (ARMA 2015 in prep.) 3

4 Mont Terri URL comparison with siting region Mont Terri URL exemplary region ZNO 4

5 Mont Terri URL horizontal section Highway tunnel Opalinus Clay 50m Full-Scale Emplacement (FE) Experiment 5

6 FE tunnel construction From April until September m long, approx. 3m diameter Advance rate approx. 1m / day Pneumatic hammer & road-header Photos: COMET Daily geological mappings Panoptic scans (ShapeMetrix) 3D infrared scans (Kinect)

7 FE tunnel sections 10m 23m in total 9 sections Lisjak et. al (2014) in total approx. 60 reflector points 7

8 FE steel arch section (last 12 meters) Photo: Vogt Photo: Köhler Simulation of Zwischensiegel - section No shotcrete, no rock bolts (needed) Only steel arches (with sliding gap) & wire mesh Bedding of steel arches on flexible grout-injected hose (similar to Bullflex system) 8

9 FE shotcrete section (first 38 meters) Shotcrete with reduced ph-value dry mix application (W/C-ratio approx. 0.65) approx. 60% cement & 40% silica fume Unconfined compressive strength (UCS) (after 28 days) of approx. 42MPa on average (after 91 days) of approx. 50MPa on average Finally: 16cm, two layers, with wire mesh Photo: Köhler 9

10 Tunneling in fault zone Tunnel parallel to strike of bedding Fault zone approx. parallel to bedding Top 20cm mapping by swisstopo

11 Tunnel wall deformation measurements Example of monitoring section C3 Lisjak et. al (2014) Renovation of invert Average displacement vectors in the shotcrete section 11

12 Shotcrete vs. steel arch section Example from 2 of in total 10 measurement sections Shotcrete Steel arch (with sliding gap!) Deformations sketched with magnification factor of 20! Fault zone in lower right corner to middle of the tunnel face Fault zone in the middle of the tunnel face 12

13 Faulty tunnel invert Damaged shotcrete (green arrow) Non-circular excavation profile (blue arrow) Poor quality of shotcrete in the invert / lower section of the tunnel (magenta arrow) renovation paid by construction company Laserscan Photo: Vogt 13 10cm

14 Renovation of invert After renovation (Sept. 2012) until end of backfilling / construction of plug (March 2015) stable / no problems!

15 Instrumentation before tunnel construction Diagonal view towards FE-A cavern not part of LUCOEX Multi-packer systems In total ca. 960 sensors and measurement points were installed mainly 2011 (FE instrumentation phase 1 of 4): - 6 boreholes with multi-packer systems, 6 intervals each (for pressure and temperature monitoring) - 2 boreholes with single-packer systems, 1 interval each (for pressure and temperature monitoring) - 2 boreholes with inclinometer-chains, 40 segments each Inclinometers + Fibre optical cables - 610m of fiber-optical cable on inclinometer chasing for distributed temperature sensing (Raman effect; resolution 1m; precision 0.1 C) 15

16 During the tunnel excavation Borehole Foto: COMET Inclinometer chain Interval Packer 16

17 exemplary measurements at one tunnel section Comparison of porewater pressure with settlement above gallery (inclinometer) at GM31 Water pressure, packer interval Settlement, horizontal inclinometer chain 17

18 Measurements during the FE tunnel excavation Interval pressures in 2 multi packer systems closest to the FE tunnel Interval pressures [kpa] Tunnel advance [m] Tunnel advance [m] Cross section showing interval positions; radial distance to tunnel wall m 18

19 Measurements during the FE tunnel excavation Temperature in the rock mass during the tunnel construction measured with the optical fibre installed on the inclinometer casing Heat from e.g. lights, people, machinery, etc. Date Temperature [ C] Tunnel portal [m] 19

20 Summary «Tunneling» FE tunnel was constructed 2012 in Opalinus Clay at the Mont Terri URL. Tunnel was constructed parallel to the strike of bedding & to a fault zone. Tunnel with 3m diameter & 50m length & 2 different support systems (first 38m with shotcrete and last 12m with steel arches). Steel arch section behaved favourable (esp. shortly after excavation). Shotcrete section initially showed an asymmetric tunnel wall convergence with high deformation rates failure of the invert. Shotcrete in the invert did not meet the quality requirements. Faulty shotcrete had to be replaced by the construction company. After the invert renovation (Sept. 2012) until the plug construction (March 2015) no further problems with tunnel stability were observed. Feasibility of constructing a repository tunnel in an over-consolidated clay-stone using standard industrial equipment was successfully verified. A dense instrumentation (installed before the excavation of the tunnel) recorded interesting and useful mine-by data. 20

21 Thank you for your attention! Herwig R. Müller Hardstr. 73, 5430 Wettingen, Switzerland Telephone: Mobile: Photo: Vogt