Sample Disturbance of Onsøy Clay Due to Gas Exsolution
High quality block clay samples at Onsøy were obtained by using the Sherbrooke sampler. Pore water with various degrees of gas dissolved were introduced to soil specimen under a back pressure simulating 1500 m water depth. Then total stresses were released, resulting in gas coming out of solution before trimming samples for advanced tests. Results from both Triaxial compression tests (CAUC) and Direct simple shear tests (DSS) showed that sample disturbance is increasing due to gas exsolution up to η = 20% and there is less increase in effects on undrained shear strength for η = 20 to 67%. Δe/ei and anisotropy ratio indicate that sample disturbance due to gas exsolution has more influence on DSS and CRSC tests than on CAUC tests. CRSC tests showed that preconsolidation stress is decreasing with increasing degree of gas saturation. Tube sampling disturbance of onsøy clay from previous study is discussed and compared with disturbance due to gas coming out of solution.
KeywordsGas exsolution Undrained shear strength Sample disturbance Degree of gas saturation
The authors would like to acknowledge constructive discussions with NGI colleagues and the support from the Norwegian Deepwater Programme - Seabed Project, as represented by Statoil. The Norwegian Research Council has also given financial support through the Norwegian Geotest Site Project where Onsøy is one of the sites being developed as part a large infrastructure facility for future research related to geotechnical engineering.
- 1.Lunne, T., Berre, T., Strandvik, S., Andersen, K.H., Tjelta, T.I.: Deepwater sample disturbance due to stress relief. In: Proceedings OTRC Conference, April 2001, pp. 64–85 (2001)Google Scholar
- 2.Yang, S.L., Lunne, T., Andersen, K.H., Tjelta, G.: Experimental study on effect of stress relief and gas exsolution on sample quality. In: Proceedings on Smarter Solutions for Future Offshore Development, London, pp. 332–337 (2017)Google Scholar
- 3.Bjerrum, L.: Problems of soil mechanics and construction on soft clay. In: proceedings of the 8th International Conference on Soil Mechanics and Foundation Engineering, Moscow, vol. 3, pp. 111–159. A.A. Balkema, Rotterdam (1973)Google Scholar
- 5.Hight, D.W., and Leroueil, S. 2003. Characterization of soils for engineering purposes. In: Tan, T.S., Phoon, K.K., Hight, D.W., Leroueil, S. (eds.) Proceedings of the International Workshop Characterization and Engineering Properties of Natural Solid, Singapore, 2–4 December 2002, vol. 2, pp. 149–162. A.A. Balkema, Rotterdam (2002)Google Scholar
- 6.Ladd, C.C., DeGroot, D.J.: Recommended practice for soft ground site characterization: arthur casagrande lecture. In: Culligan, P.J., Einstein, H.H., Whittle, A.J. (eds.) Soil and Rock America 2003: Proceedings of the 12th Panamerican Conference on Soil Mechanics and Geotechnical Engineering, Cambridge, 22–26 June 2003, vol. 1, pp. 3–57. VGE Verlag Gluckauf, Essen (2003)Google Scholar
- 10.Lunne, T., Long, M., Forsberg, C.F.: Characterisation and engineering properties of Onsøy clay. In: Tan, T.S., et al. (ed.) Characterisation and Engineering Properties of Natural Soils, Balkema 2003. Proceedings of the International Workshop, Singapore 2002, vol. 1, pp. 395–427 (2003)Google Scholar
- 11.NGI: Studying the effect of gas on soil properties measured on deepwater samples. Results of laboratory tests for evaluation of disturbance due to gas. NGI project 20001411-3. Final report dated on 5 March 2002 (2000)Google Scholar
- 12.Sandbækken, G., Berre, T., Lacasse, S.: Oedometer testing at the Norwegian Geotechnical Institute. Consolidation of Soils: Testing and Evaluation: A Symposium. Fort Lauderdale, Fla. 1985. American Society for Testing and Materials, vol. 892, pp. 329–353. Special Technical Publication (1986). Also Published in: Norwegian Geotechnical Institute, Oslo. Publication, vol. 168 (1987)Google Scholar
- 13.Lunne, T., Berre, T., Strandvik, S.: Sample disturbance effects in deep water soil investigations. In: Offshore Site Investigation and Foundation Behaviour 1998, New Frontiers, SUT Conference London 1998, pp. 199–220 (1998)Google Scholar