Talk:Critical state soil mechanics

Sanpaz et al: Good job on this page! I think a history section would be useful: Osborne Reynolds, Donald Taylor, Casagrande, leading up to Roscoe, Schofield and Wroth. This info is all in the Schofield 2006 reference you mention. I put some of this history on the geotechnical engineering page. Maybe some of this could be borrowed for this page too. Maybe a reference to DM Wood's book, or Powrie, Budhu text books would bring it up to the present. Blkutter (talk) 08:05, 10 August 2010 (UTC)

Personal atacks: This statment meets not the requirement of personal attack as a) it is documented in a respected biography of Skempton and so is *historical fact* b) both parties are disceased and c) the comment is very germane to the discussion that CSSM is skolastik.

>> The critical-state and concepts surrounding it have a long history of being "scholastic," with Sir Alec Skempton, the “founding father” of British soil mechanics, attributed the scholastic nature of CSSM to Roscoe, of whom he said: “…he did little field work and was, I believe, never involved in a practical engineering job.” (Niechcial, 2002).

For this reason I add it now. Efischer80 (talk) 15:13, 17 December 2017 (UTC)

Critique
This section is written with the purpose of convincing people that Critical State Soil Mechnics is wrong, and that the theory of DSSM is correct. An acceptable approach, in my opinion would be would be to make a short criticism here (e.g., one or two sentences), and create a separate page describing the theory of DSSM objectively. This "Critique" section has three paragraphs that do not cite a source. The last paragraph cites one author, Paul Joseph, that has published several articles critical of CSSM, but his work has not yet been adopted in any text books or secondary sources; on the other hand, critical state soil mechanics is presented in many modern textbooks. I encourage the editor to create a separate page on DSSM and to link to that page from this one.

I will delete the sentences devoted to personal criticism of Roscoe because personal attacks are not allowed on Wikipedia No personal attacks. Blkutter (talk) 22:32, 25 July 2016 (UTC)

I would like to add the following section to this page. Unless hearing to the negative I will do so in 30 days.

Critique: Critical state and elasto-plastic soil mechanics have been the subject of criticism ever since they were first introduced. The key factors driving the critique are primarily the assumption that soils behave like metals, specifically, that they are implicitly made of isotropic point particles. Real soils have particles with anisotropic properties that strongly determine observed behavior. Consequently, models based on a metals based theory of plasticity are not able to model behavior of soils that is a result of anisotropic particle properties. Because of this elasto-plastic soil models are only able to model "simple stress-strain curves" such as that from isotropic normally or lightly over consolidated "fatty" clays, i.e., CL-ML type soils constituted of very fine grained particles. Also, in general, volume change is governed by considerations from elasticity and, this assumption being largely untrue for real soils, results in very poor matches of these models to volume changes or pore pressure changes. Also, elasto-plastic models describe the entire element as a whole and not specifically conditions directly on the failure plane, as a consequence of which, they do not model the stress-strain curve post failure, particularly for soils that exhibit strain-softening post peak. Finally, most models separate out the effects of hydrostatic stress and shear stress, with each assumed to cause only volume change and shear change respectively. In reality, soil structure, being analogous to a "house of cards" shows both shear deformations on the application of pure compression, and volume changes on the application of pure shear.

For these reasons, critical-state and elasto-plastic soil mechanics have been subject to charges of scholasticim, with charges that the tests to demonstrated its validity are restricted to "conformation tests" where only simple stress-strain curves are demonstrated to be modeled satisfactorily. The critical-state and concepts surrounding it have a long history of being "scholastic," with Sir Alec Skempton, the “founding father” of British soil mechanics, attributed the scholastic nature of CSSM to Roscoe, of whom he said: “…he did little field work and was, I believe, never involved in a practical engineering job.” (Niechcial, 2002).. In the 1960's and 1970's, Prof. Alan Bishop at Imperial College used to routinely demonstrate the inability of these theories to match the stress-strain curves of real soils. More recently, Joseph has suggested that critical-state and elasto-plastic soil mechanics meet the criterion of a “degenerate research program” a concept proposed by the philosopher of science Imre Lakatos, for theories where excuses are used to justify an inability of theory to match empirical data. Lakatos was commenting in general about scientific programs and probably did not even know that a field like soil mechanics existed, which makes his comments all the more powerful. Additional criticisms are that the theory is "descriptive," i.e., only describes known behavior and lacking the ability to either explain or predict standard soil behaviors such as, why the void ratio in a one dimensional compression test varies linearly with the logarithm of the vertical effective stress. This behavior, critical state soil mechanics simply assumes as a given.

Refs: Niechcial, J. (2002). A Particle of Clay: The Biography of Alec Skempton, Civil Engineer. Whittles Publishing. ISBN 1-870325-84-2. Joseph, Paul G. (2013). "Dynamical systems based soil mechanics (DSSM), a short self-study course".

Efischer80 (talk) 11:59, 24 July 2015 (UTC)

Added. — Preceding unsigned comment added by 70.167.21.20 (talk) 13:20, 24 August 2015 (UTC)