| 1. |
- Degago, S. A., et al.
(författare)
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Time- and stress-compressibility of clays during primary consolidation
- 2010
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Ingår i: Numerical Methods in Geotechnical Engineering - Proceedings of the 7th European Conference on Numerical Methods in Geotechnical Engineering, NUMGE 2010, Trondheim, Norway, 2-4 June 2010. - : CRC Press. - 9780415592390 ; , s. 125-130
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Konferensbidrag (refereegranskat)abstract
- The existence of creep deformation during primary consolidation has been widely accepted; however, there are still contradicting opinions on the mechanisms that govern creep during the primary consolidation phase. This study aims to assess creep effects during primary consolidation such that it is possible to critically evaluate and challenge some of these opinions. A special type of interconnected oedometer tests were designed and conducted. The tests were numerically studied using a soil model based on the isotache concept. These analyses show that the isotache concept can capture the important features of the tests well and thereby describe the time- and stress-compressibility of a soil during the entire soil compression phase.
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| 2. |
- Degago, S.A., et al.
(författare)
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Use and misuse of the isotache concept with respect to creep hypotheses A and B
- 2011
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Ingår i: Geotechnique. - 0016-8505 .- 1751-7656. ; 61:10, s. 897-908
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Tidskriftsartikel (refereegranskat)abstract
- Time-dependent settlements of thick in situ clay layers are normally analysed based on results of thin laboratory specimens. However, the time used to complete primary consolidation is significantly different for laboratory specimens and in situ soil layers. Two totally different cases, referred to as creep hypotheses A and B, have been used as a basis of discussion to assess the effect of creep during the primary consolidation phase. Several laboratory and field experiments have been conducted to study the effect of soil layer thickness on the time-dependent compressibility of a soil layer. Some of these tests seemed to support hypothesis A, others hypothesis B, and in some cases showed a behaviour between the two. As a result this question has continued to be a controversial topic among researchers, and remains to be an issue that needs to be resolved. In this study, some relevant experimental investigations from the literature are thoroughly studied and critically reviewed, and also explained consistently using the isotache concept. This work indicates that the isotache approach can capture the main characteristics of the time-dependent compressibility of clays during both the primary and secondary consolidation phases. It is also shown that the misuse of the isotache concept, as reported in the literature, may give a confusing picture of reality. Based on the considered data, it is demonstrated that the measured time-dependent compressibility of clays agrees well with hypothesis B.
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| 3. |
- Jostad, H. P., et al.
(författare)
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A procedure for determining long-term creep rates of soft clays by triaxial testing
- 2022
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Ingår i: European Journal of Environmental and Civil Engineering. - : Informa UK Limited. - 2116-7214 .- 1964-8189. ; 26:7, s. 2600-2615
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Tidskriftsartikel (refereegranskat)abstract
- The paper presents a procedure for determining a significantly larger range of creep rates (isotaches) of soft clays than found from standard incremental loading oedometer tests. The test is performed in a triaxial apparatus by first loading up to the virgin compression line at a relevant effective stress level and then determine the creep rates at different stress states along an unloading branch keeping the horizontal to vertical effective stress ratio constant. The test procedure is tested on a soft Norwegian plastic marine clay. Challenges due to the non-linear behaviour of natural soft clays where the standard creep and compression indexes are not constant values are demonstrated, and recommendations for how to account for this effect are given. The obtained results from the test are also compared with results from a parallel long-term creep phase in a standard oedometer apparatus taken from the same block sample.
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| 4. |
- Pazmiño, Sebastián A., et al.
(författare)
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A generalized 3DLS-DEM scheme for grain breakage
- 2022
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Ingår i: Computer Methods in Applied Mechanics and Engineering. - : Elsevier BV. - 0045-7825. ; 399
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Tidskriftsartikel (refereegranskat)abstract
- We introduce a new generalized 3DLS-DEM (3D Level Set Discrete Element Method) scheme that incorporates grain breakage, taking an important step towards realistic modeling at the micro-scale with DEM. For the first time, simulating thousands of real 3D grains that are able to break, which was possible due to the algorithm used for grain breakage. The presented scheme is not only capable of efficiently simulating grains with real shapes but also preserving mass and grains morphology with high fidelity when breakage occurs. Hence, with this approach, further works within the original 3DLS-DEM scheme could take into account other physical phenomena at the grain-scale such as electrostatic induced cohesion, heat transfer, or the presence of a fluid, etc. On the other hand, the breakage process modified grain size and roundness distributions, which, in turn, might change the strength and critical state of the sample. Withal, the overall process seems to suggest that grain breakage may be a sufficient condition to exacerbate the prevalence of shear banding within the sample. Finally, our model is able to perform breakage on several real 3D grains of a sample consisting of thousands of grains in a generalized 3DLS-DEM scheme.
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