Department Of Civil & Structural Engineering.

Transcription

1 Department Of Civil & Structural Engineering. Minutes of ISSMGE TC205 Technical committee: Safety and Serviceability in Geotechnical Design Tenth meeting, 9 th February 2015, by tele-conference (13:00-15:00 UTC) Participating: Brian Simpson (UK, chair) Peter Day (South Africa), Tim Länsivaara (Finland), Trevor Orr (Ireland), Adriaan van Seters (Netherlands), Jorgen Steenfelt (Denmark), Michael Lodahl (Denmark). Secretariat: Apologies: Absent: Sam Clarke (UK), Colin Smith (UK) Kerstin Lesny (Germany), Tony Allen (USA), KK Phoon (Singapore), Maria J. Avecillas (Ecuador), Lech Bałachowski (Poland), Richard Bathurst (Canada), Franco Francisca (Argentina), Roger Frank (France), Takashi Hara (Japan), Yusuke Honjo (Japan), Hongwei Huang (China), Petr Koudelka (Czech & Slovak Republics), Anders Kullingsjö (Sweden), Iacint Manoliu (Romania), Sam Paikowsky (USA), Agustin Popa (Romania), W.K. Pun (Hong Kong), Rodrigo Salgado (USA), Bernd Schuppener (Germany), Masahiro Shirato (Japan / India), Antonio Soriano (Spain), Marco Uzielli (Italy), Balazs Vasarhelyi (Hungary), Aida S. Zhakulin (Kazakhstan), Limin Zhang (Hong Kong), Fred Kuhawy (USA). 1. Introductions. 2. Acceptance of agenda, noting any other business. The agenda was accepted. 3. To note minutes of the previous meeting (7 th October 2014) - Document TC To note new members. Document: TC

2 5. Actions from previous meeting not otherwise on agenda. a. 5a. Members to send images of themselves to Sam Clarke. (Current photos may be seen in the document Photos of TC members.pdf on the TC205 website) b. 5b. Members to contribute suitable references related to SLS. Outstanding; Andrew Bond to check information he has received in relation to EC7/EG8. Colin Smith to Andrew regarding this. (PMN: Andrew had already supplied this and it will be circulated.) c. 5c. Sam Paikowski to circulate briefing document on work done on SLS. Outstanding. Colin Smith to Sam regarding this. d. 5d. Trevor Orr to report on discussions with Tim Lansivaara about his Paris paper on risk. Tim Lansivaara to circulate copy of paper Safety concepts for slope stability. (PMN: Done.) 6. Technical topic: a. Closure on previous discussion: Methods of calculating the serviceability limit state in geotechnical design Colin Smith to write up previous discussion. b. Reliability. Discussion to be based around the following papers: 'Dutch approach to Geotechnical design by Eurocode 7, based on probabilistic analyses' introduced by Adriaan van Seters 'Calibrating partial factors for Danish railway embankments using probabilistic analyses' introduced by Michael Lodahl. Selected notes from the discussion are presented in the Appendix. 7. Progress on TC205 State of the art report on Safety and Serviceability in Geotechnical Design. Colin Smith will be working on this over the coming months. 8. Meetings a. 16th ISSMGE European conference, Edinburgh, September conference papers have been submitted by members on TC205 topics. Current plans are for a TC205 workshop back-to-back with a workshop on numerical methods which will address Eurocode related topics. Plans require further development. Current ideas include coverage of ground anchors, water pressures, characteristic values and output of ETC10. Brian Simpson, Colin Smith, Trevor Orr. b. ISSMGE pan-american conference in Buenos Aires, November It was noted that TC304 are involved in this. Members are asked to express any enthusiasm for a TC205 involvement. c. ISGSR Conference Rotterdam October 2015 Tim & Adriaan currently have papers in this conference. Document: TC

3 d. 15th ISSMGE Asian Regional Conference in Fukuoka, Japan, 9-13 November Noted that TC304 are having a session. e. 19 th ISSMGE International conference, Seoul, September f. 10th Int. Conf. on Stress Wave Theory and Testing Methods for Deep Foundations, June 2016 Boston MA., USA g. TC304 & ASCE GI-RAM Mini-Symposium (MS-15) Reliability of Geotechnical Structures in ICASP 12, July 12-15, 2015, Vancouver Canada 9. Discussion topics for next meeting May State of the Art Report : Colin Smith to circulate the document for discussion. SLS issues: Contributions by Sam Paikowski and Andrew Bond (see 5b and 5c above) to form basis for discussion in next meeting. Colin Smith to circulate documents for discussion. 10. TC205 honour lecture at next ICSMGE ISSMGE appear to be proposing that a series of lectures rather than a single lecture be associated with each Honour Lecture. It was felt that such a series of lectures would be too much work for TC205 to commit to and that this would not be pursued at present. 11. Internet forum topics propose ideas for topics for debate. It was suggested that some recent work by Brian Simpson and Andrew Lees on SLS calculations could form a good forum topic. Colin Smith to contact Andrew Lees. 12. Any other business. It was noted that all members need to contact their representative institution to make sure they are the named contact for TC205. Secretariat to remind all members of the need to do this. Timing of meetings was discussed, there were no strong feelings about current timings. Secretariat to send out questionnaire regarding ideal meeting times for eastern / western members. Appendix: Notes of Discussion Topic: Reliability (Please note that the following notes are based on a discussion and may not provide definitive statements about any given topic). The following papers were discussed. Michael R. Lodahl, Kristian T. Brødbæk, Carsten S. Sørensen (2014) Calibrating partial factors for Danish railway embankments using probabilistic analyses. Journal of Rock Mechanics and Geotechnical Engineering 6 (2014) Document: TC

4 Ton VROUWENVELDER, Adriaan van SETERS and Geerhard HANNINK (2013) Dutch approach to Geotechnical design by Eurocode 7, based on probabilistic analyses. Modem Geotechnical Design Codes of Practice. P. Amold e/ a/. (Eds.). los Press. Following issues/comments/questions were raised: Calibrating partial factors for Danish railway embankments using probabilistic analyses Current Danish NA partial factor on undrained strength is 1.8. This is based on previous practice which employed a factor of 1.8 for foundations and 1.5 for stability and earth pressures. In order to avoid ambiguity, 1.8 was adopted in all cases in the Eurocode. Previous Danish practice made significant use of shear vane data. Reliability studies showed that a partial factor of ~1.5 was more appropriate for the railway embankments studied. This in part is due to averaging effects over large slip surfaces. For smaller slips the required factor gets closer to 1.8. This depends on the definition of the characteristic value 5% fractile on mean or distribution? This highlights the importance of selecting the characteristic value of a parameter on the basis of the limit state being assessed. Should the importance of the small scale/large scale issue be dealt with by the characteristic value or the partial factor? This topic was noted for future discussion in TC205. The railway study has led the railway authorities to re-evaluate partial factors for other projects. The cost/benefit in the case reported in the paper was significant. It was possible to undertake the study based on existing information without the need to conduct further SI. However this approach is only likely to be used on large projects with long time scales. The study in this case took ~ 6 months. A high beta value of 5.2 was used in the study. This was to match the same value used for bridges. Dutch approach to Geotechnical design by Eurocode 7, based on probabilistic analyses Sensitivity studies based on multiple simulations were carried out to determine appropriate alpha values. Table 5, the 1.1 factor on weight for shallow foundations is a divisor. Highest safety factor is attributed to the most uncertain parameter with the largest influence on the design. Thus for example the factor on c is 1.6 for shallow foundations but ~1.0 for anchored sheet pile walls, while the factor on tan' is ~1.15 in both cases. However since the factoring on c may be scenario dependent, the factors on c in the Dutch NA were set above 1.0. Document: TC

5 General Should reliability studies be more relevant to specific projects or code drafters (in terms of partial factors and/or guidance on undertaking reliability based studies?) Document: TC