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- Bernander, Stig, et al.
(författare)
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Downhill progressive landslides in long natural slopes: triggering agents and landslide phases modeled with a finite difference method
- 2016
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Ingår i: Canadian geotechnical journal (Print). - : Canadian Science Publishing. - 0008-3674 .- 1208-6010. ; 53:10, s. 1565-1582
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Tidskriftsartikel (refereegranskat)abstract
- A large landslide in Tuve (Gothenburg, Sweden 1977) initiated the development of a model for slope stability analysis taking the deformation-softening of soft sensitive clays into consideration. The model studies triggering agents and five phases in progressive slope failure are identified: (1) in-situ, (2) disturbance, (3) unstable ‘dynamic’, (4) transitory (or permanent) equilibrium, and (5) ‘global’ failure. The clay resistance in these phases may differ widely; mostly due to different rates of loading. Two time dependent failure criteria are defined: (i) the triggering load condition in the disturbance Phase (2), and (ii) the transitory equilibrium in Phase (4), indicating whether minor downhill displacements or a veritable landslide catastrophe will occur. The analysis explains why downhill landslides tend to spread over vast areas of almost horizontal ground further down-slope. The model has been applied to landslides in Scandinavia and Canada. Three case studies are briefly discussed. The model is a finite difference approach, where local downhill deformations caused by normal forces is maintained compatible with deviatory shear deformations above the potential (or the established) failure surface. Software and an easy-to-use spreadsheet are introduced as well as recent developments. See also Video Abstract.
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| 2. |
- Bernander, Stig, et al.
(författare)
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Progressive Landslide Analysis in Canadian Glacial Silty Clay in Churchill River
- 2017
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The poster presents the risks for a progressive landslide in a natural dam. The stability will be critical when the water level is raised after the building of a hydro power plant, Bernander (2016), Dury (2017). The analysis is based on a finite difference method developed by Stig Bernander (2011), Bernander et al.(2016) The following issues will be discussed: - Material properties- Risk for liquefaction- Three possible failure surfaces: one horizontal, one inclined and one curved- Failure riska for different material propeties- The need to check the real properties of the soil
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| 3. |
- Bernander, Stig
(författare)
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Progressive landslides in long natural slopes : Formation, potential extension and configuration of finished slides in strain-softening soils
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- After the large landslide in Tuve (Gothenburg, 1977), the author began developing a finite difference model for slope stability analysis taking the deformation-softening of soft sensitive clays into consideration. In the model, the mean down-slope deformation in each element caused by normal forces is maintained compatible with the deformation generated by shear stresses. He developed software for the model and presented it at international soil mechanics conferences during the 1980-ies. In 2000 he summarized his findings in a Licentiate thesis. An easy-to-use spread-sheet has also been developed. In this thesis the author conveys his experiences of slide modeling focusing on the nature of triggering agents and the different phases that a slope may undergo before its stability becomes truly critical.
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| 4. |
- Bernander, Stig
(författare)
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Progressive landslides in long natural slopes : potential extension and configuration of finished slides in strain-softening soils
- 2000
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- A finite difference method is presented for progressive slides in long natural slopes. The method is based on a strain softening material model. A detailed worked out example is given as well as examples using a spread sheet PC program and a PC program for Windows. Several Scandinavian slides are analysed and discussed as case studies e g Tuve (1977), Surte (1951), Bekkelaget (1953), Rollsbo (1967), Rävekärr (1971), Tre-styckevattnet (1990) and Svärtaån (1938). The nature of down-slope progressive failures in natural slopes is described and the applicability of ideal-plastic failure analysis is questioned. Principles and procedures for investigation potential landslides are presented. A short historical background to the landslide problem is given in an introductory chapter.
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| 5. |
- Dury, Robin, 1994-, et al.
(författare)
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Progressive Landslide Analysis with Bernander Finite Difference Method
- 2017
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The poster presents a new Spreadsheet developed by Robin Dury (2017) to simplify the use of the Finite Difference Method developed by Stig Bernander et al (2011, 2016).It includes:- Material Properties- Finite Difference Method- Progressive failure process with five phses- Discussion- References
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| 6. |
- Elfgren, Lennart, 1942-, et al.
(författare)
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Response to and Comments on “Geotechnical Peer Review of Dr. S. Bernander’s Reports and Analysis of the North Spur”
- 2018
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The concerns regarding the stability of the North Spur can be summarized in three points:(1) None of the most critical inclined failure surfaces have been studied by Muskrat Falls Corporation. These failure surfaces may be initiated on the upstream side of the dam containment. Here the effects of the deformations, caused by the pressure of the rising water level, have to be resisted by the metastable soil layers in the North Spur. A local failure may occur progressing downwards towards the downstream side of the Spur. A catastrophic dam breach would follow. The GPRP further categorically overlooks the fact that horizontal failure planes cannot possibly represent the highest risk of instability irrespective of whether the analysis is based on the Limit Equilibrium Mode (LEM) or on the Progressive Failure Mode.(2) The stress/strain deformation properties of the porous soils in the North Spur have not been made available. Only strength properties, related to fully drained conditions, have been given. How stresses relate to simultaneous deformations under undrained (or partially undrained) conditions have not been defined in any way. Such relationships are crucially essential for any up-to-date analysis of slope stability.(3) A high risk of North Spur instability has been found related to impoundment. A series of investigatory calculations have been made, based on deformation properties from similar landslides and on a wide variety of assumed input data for possible critical failure surfaces. The results of these analyses indicated a safety factor far below 1.The peer review does not address the above three points. It gives a good view of the general conditions but also contains misconceptions, erroneous considerations and refutable comments indicating that the earlier reports by Bernander have not been fully understood by the panel members.As no up-to-date analysis of the stability of the North Spur has been provided, our conclusion is that an independent group of experts, appointed by government, should be entrusted with this important task.
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