Creep behaviour of soft clay
In spite of the well known problem related to time dependent settlements of soft clay, there are no commonly accepted methods for calculation of these settlements. This was the motivation for the CREBS (CREep Behaviour of Soft clay) Workshop 5-6 January 2006 at NGI.
After that two additional workshops have been organised: Pisa 2007 and Gothenburg 2009. This project, which started in 2006, is a result of these workshops.
The activities performed this year are as follows:
| 1. |
Evaluation of results obtained from six participants in the given hypothetical case study. Comparison of calculation models and reasons for differences in results. |
| 2. |
Presentation of results at the CREBS III workshop in Gothenburg in June 2009. |
| 3. |
Presentation of the results in a paper to NUMGE 2010 in Trondheim. |
| 4. |
Purchased a block sample from Onsøy. It was not time and budget for performing tests this year. The plan is to repeat tests performed in two coupled odometer apparatus at Chalmers by Ph.D student Samson Degago.
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| 5. |
Back-calculation of the Ellingsrud test fill by Master student Zeru Kiffle. |
| 6. |
Back-calculation of the Onsø test fill by Gustav Grimstad. |
| 7. |
Supporting and supervising Ph.D. student Samson Degago. Samson has manly studied results that support Hypotheses A. He has used the Soft Soil Creep model in Plaxis in this study. A key activity has been to study and understand the laboratory test results obtained by Professor Mesri's students.
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Example of results from the analyses of the hypothetical cases is shown in Figure 1. Figure 2 shows the three rotated yield surfaces in the elasto-viscoplastic SCLAY1S model used by Dr. Yin and Professor Karsunen in these analyses. The other models used in the analyses were based on the isotoche concept.
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| Figure 1: Calculated surface settlements |
Figure 2: Yield surfaces in the EVP SCLAY1S model by Yin & Karstunen |