Talk:Shear strength (soil)

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Contents 1 Missing points 2 Move soils information 3 Clarificaton 4 Measurement 5 Critical State Vs. Steady State 6 Maintanance

[edit] Missing points

Two points seem missing in this article. Cohesion is not a function of negative pore pressure; it is caused by diagenetic forces between the solids in soil. Apparent cohesion is caused by negative pore pressure; that force dissipates as the negative pore pressure is satisfied and the soil shifts to the drained condition. Secondly, φ is the internal friction angle. It is not a resistive force. The resistive force from the friction angle is N*tan(φ); the resistance is proportional to the overburden pressure, N.

The term 'angle of internal friction' is prevalent in older literature, but is slightly misleading. The phi angle in soils is brought about by a more complex interaction of particles than the term 'friction' suggests, particularly in cohesive soils, but also in granular soils, where confining pressure, initial density, particle shape and angularity, orientation of particles, and physico-chemical effects such as cementation and bonding influence the phi angle, and ultimately the shear strength of a soil. A more 'correct' and generic term which should be used is 'angle of shearing resistance', as it encompasses all these effects not merely Coulomb friction. In the least, Friction should link to the main Wikipedia friction page: http://en.wikipedia.org/wiki/Friction I'd suggest shear strength be expanded or carefully linked to other pages that cover failure criteria; Linking to pages on Mohr-Coulomb Theory http://en.wikipedia.org/wiki/Mohr-Coulomb_theory, and for undrained shear strength, Tresca http://en.wikipedia.org/wiki/Henri_Tresca. Plasticity, http://en.wikipedia.org/wiki/Plasticity_%28physics%29, and Yield http://en.wikipedia.org/wiki/Yield_%28engineering%29 as general concepts for defining shear strength. But individual pages specific to shear strength of soils (for example) could be created, since there is much to expand on in this area. GeoEng 09:05, 11 March 2007 (UTC)

OK I decided I had nothing better to do, and had a go at editing this page (my first time editing on wikipedia, so dont shoot me). I have added non-existent links to Critical State Theory and Modified Cam Clay, in the hope someone (maybe me) will write entries on these. This article needs references I know. And links to similar articles. GeoEng 18:37, 11 March 2007 (UTC)

Thanks for your contributions; I'll try to help you out if I have time. Basar 19:53, 11 March 2007 (UTC)

Added some references and further info relating to cohesion and friction from those references. Really its just one actual reference at this stage (ref 2) by Prof. Schofield, and the others are cited in that document. May add some stuff from Prof. Burland if I get around to it, on 'post rupture' strength. This document needs some figures... i'll need to get around to those as well:) —The preceding unsigned comment was added by GeoEng (talk • contribs) 00:43, 18 March 2007 (UTC).

I am not sure I agree re. the cohesion concept presented in below--it may be true for non-cohesive sils, but for coehsive soils ex. "fat clays", inter-particle attraction forces would cause C to be non-zero at zero confining stresses. In otherwords, other than diagenetic forces, there is the plain old inter-particle attraction to consider--no? Please let me know why I may be mistaken. Pathikoll 10:18, 20 July 2007 (UTC)

[edit] Move soils information

It seems to me that shear strength of soils should have its own article, perhaps shear strength (soil) or shear strength of soil. I'll move it if no one objects. Basar 19:53, 11 March 2007 (UTC)

Good idea. Still need to leave the basics at this site with a "Main article" link. I have a preference for Shear strength (soil), but, eh, no big yank one way or t'other. ZueJay (talk) 20:05, 11 March 2007 (UTC)

[edit] Clarificaton

I would like to make a clarification re. the statement in the article that I have copied below:

"However, what is being plotted is not "true" cohesion, but is actually due to interlock of particles."

While this is no doubt possible for sands, for clays the cause is not so much intelock of particles, but rather inter-particle attractive forces. These are not quite the same and I would like to distinguish between the two if there is no objection. Pathikoll 18:09, 19 July 2007 (UTC)

Am removing this statement that I added at the bottom of critical state as it is valid not just to the CS, but to all other theories as well: "In recent years, critical state soil mechanics appears to have reached a dead end. For example, it has been unable to explain the emperical SHANSEP relationship. It may be that a theory which ignores soil structure is essentially limited in what it can explain."

Am adding the last line back at the end of the introduction: "It may be that a theory which ignores soil structure is essentially limited in what it can explain." —Preceding unsigned comment added by Pathikoll (talk • contribs) 18:51, 25 October 2007 (UTC)

Am removing this text as I am not sure why it is here, the topic is about soil shear and not advanced soil mechanics: "Advanced soil mechanics is often taught in specialist masters degree programs, and the prerequisite to practice as a geotechnical engineer often requires such training, particularly with the use of modern numerical techniques such as finite element analysis and with the adoption of critical state soil models."

[edit] Measurement

Could expand on measurement e.g. by vane, Torvane. —DIV (128.250.204.118 09:15, 10 October 2007 (UTC))

[edit] Critical State Vs. Steady State

There seems to be a lack of understanding of the difference between the critical state and the steady state. I am personally in contact with both Andrew Schofield and Steve Poulos, the two representatives of these respective states.

Thus the Critical State occurs at the quasi-static strain rate. It does not allow for differences in shear strength based on different strain rates. Also at the critical state, there is no particl alignment, all grains presumed to have broken to form spherical shaped grains.

The steady state can occur at any different strain rate, but has a slightly different value depending on the strain rate at which it is measured. Thus the steady state shear strength at the quasi-static strain rate would seem to correspond to the critical state shear strength. But it does not as the steady state does not assume that grains are crushed to form spherical particls. Rather it states that the grains align in the direction of shear, forming a special structure called the steady state structure. —Preceding unsigned comment added by Pathikoll (talk • contribs) 15:35, 25 November 2007 (UTC)

[edit] Maintanance

Am moving all notes to references, and linking them in-line using Harvard Citation already in place —Preceding unsigned comment added by Pathikoll (talk • contribs) 15:55, 1 November 2007 (UTC) Adding back a link to a review of Andrew Schofield's new book. This review was requested and approved by Andrew and as such does not qualify as spam (under which criterion it had been removed.) —Preceding unsigned comment added by Pathikoll (talk • contribs) 12:42, 6 April 2008 (UTC)