Geological and geotechnical investigations for TBM projects

Transcription

1 Geological and geotechnical investigations for TBM projects Pål Drevland Jakobsen Norwegian University of Science and Technology

2 Contents Why and when execute ground investigations Examples of executed ground investigations and cost Comparison (TBM versus D&B / Hard rock versus soft ground) Conclusive remarks and further research References and sources of information Norwegian University of Science and Technology 2

3 Introduction why and when execute ground investigations (ITA WG 2 report no 15) Verification of rock/soil Indication of stability / excavation challenges Find existing geo-data. Feasibility Concept study/design Validate feasibility Drilling (probe or core) Find tunnel alignments and geometry Prepare geoprofiles Excavation method Documentation Handling of claims Probe drilling TBM data analyses Back-mapping Execution / excavation Detailed design Validate concept study/design Laboratory tests Detailed profiles Excavation method Norwegian University of Science and Technology 3

4 Level of GI are dependent on Available knowledge/documentation of the geology Contract (e.g. unit price contracts versus design/build contracts) Complexity of project (e.g. tunnel size, depth, neighbors) Norwegian University of Science and Technology 4

5 DWA 125E Norwegian University of Science and Technology 5

6 Case 1: Wistula river crossing Sub-river project in Gdansk, Poland 2 x m long TBM bored tunnels (13.3 m diameter) Mainly clay and sandy soil conditions Extensive pre-investigation scheme Norwegian University of Science and Technology 6

7 Wistula pre-investigation scheme General geotechnical tests + Standard Penetration Test (SPT) Mechanical tests Environmental tests Abrasivity tests Norwegian University of Science and Technology 7

8 Case 2: The Follo line Photos courtesy of AGJV Norwegian University of Science and Technology 8

9 Follo line field tests Colour Number of tests Comments 420 Probe-drilling for Follo line project 712 Probe drilling from other projects 14 Well-drillings (pore pressure measurements) + Lugeon 20 Core drilling holes m cores 59 Seismic profiles (velocity in the ground) m Norwegian University of Science and Technology 9 19 Resistivity profiles (identify planes of weaknes) m.

10 Follo line rock mechanical tests (lab) Norwegian University of Science and Technology 10

11 Follo line additional tests (AGJV) Additional resistivity testing and seismic refraction Core drilling + various laboratory tests Measure While Drilling Analyses / probe-drilling Optical televiewer measurements Norwegian University of Science and Technology 11

12 Case 3: Røssåga Tender and design process as a conventional D&B project Desk studies of geological maps Two core holes, mainly to assess the rock mass properties around the underground power-house Evaluation of experiences from the hydropower project in the 50 s Norwegian University of Science and Technology 12

13 Case 4: Ulriken Existing parallel tunnel that has been mapped as GI About 1 DRI/CLI sample per km tunnel Probe-drilling Refraction seismic Norwegian University of Science and Technology 13

14 Lessons learned from Ulriken GI Possible need for rock stress measurements UCS values in the tender documentation are based on measured values from Fløyfjell tunnelen Representability? Increase rock mass mapping of the existing Ulriken tunnel Norwegian University of Science and Technology 14

15 Comparision between apples and pears From Norwegian University of Science and Technology 15

16 Cost for GI (After ITA WG2 and own data) Urban short tunnels in soft ground Long tunnels in rock Norwegian University of Science and Technology 16

17 D&B and TBM (SVV publication 101) Norwegian University of Science and Technology 17

18 D&B and TBM (SVV publication 101 and new data) Norwegian University of Science and Technology 18

19 Hard rock tunnel investigations Factor TBM versus D&B Examples of investigations Boreability Substantially more for TBM Intact rock strength Rock mass quantification Abrasivity and rock hardness Water Equal Water head and estimated amounts Settlement sensitivity Stability Environmental impact Equal to less (potentially higher rock Equal to less (reduced blast vibrations). Rock mechanical tests Rock mass quantification Use of excavated material Trial blasting/rock mass sonic velocity Norwegian University of Science and Technology 19

20 Soft ground tunnel investigations Use existing data/knowledge in feasibility add pin pointed tests to reduce risk in design phase. Use or discharge of excavated muck Soil types Organic content Boulders Sieve curves etc Mechanical tests Abrasivity Water head Relative constant or varying? Norwegian University of Science and Technology 20

21 Recommendations for investigation density Provide values for all the representative zones Mechanical rock/soil properties Boreability properties including abrasivity Water head and amounts Mixed face? The easy solution for the project owner is to describe the share of materials How to assess this? Norwegian University of Science and Technology 21

22 Conclusive remarks The pre-investigation scheme is highly dependent on: Anticipated ground conditions from the feasibility study The anticipated complexity of the project The selection of contract type ( Who is paying for the risk who is paying to reduce the geological risk? ) Further details and experiences is planned to be published at WTC2017 in Bergen Norwegian University of Science and Technology 22

23 Acknowledgements and references Aknowlegdements to Bjørnar Gammelsæter (JBV), Leon Eide (JBV), Marek Multan (Marti- Norge AS) for sharing experiences on GI. Norsk Bergmekanikk gruppe Veileder for bruk av Eurokode 7 til Bergteknisk prosjektering. November 2011 (In Norwegian) Gammelsæter, B., Ground investigations for the Follo line. Personal communication April Eide, L., Ground investigations for the Ulriken tunnel. Personal communication April 2016 ITA WG 2. Strategy for site investigation of tunnelling projects. May DWA-A 125E Pipe Jacking and Related Techniques, German Association for Water, Wasterwater and Waste. December 2008 Statens vegvesen Publication 101. Riktig omfang av undersøkelser for berganlegg (In Norwegian). Norwegian University of Science and Technology 23