Dear Collegue,

Liquefaction problem is related via unconsolidated silty to sandy soils, not via fine grained soils called clays, including many clay minerals. Clayey soils have another soil stability problems like expansion and different value of compansion and/or subsidence under over loading of settlement loads.

As I know that montmorillonite is included in smectite minerals and as the 2:1 type mineral that may swell in wet condition and shrink when it is dry.

The subsidence problem may occur in wetland soil or peat soil after it has been drained.

Liquifaction generally associated with silty sands and excessive pore pressure development. However check out you tube for film of the Rissa Landslide associated with highly sensitive clay soils (sensitivity is a measure of peak to residual (ie disturbed) shear strength), "Subsidence" is too generalised a term for anyone to link cause / effect. Do you mean consolidation settlement of soft clays, shrink / heave of swelling clays (montmorrillinite is likley to have a role here), differential settlement due to variable soil thicknesses, or perhaps punching failure through a dessicated crust?

Dear Keith Nicholls,

My point of view is the second of your question "shrink / heave of swelling clays (montmorrillinite is likelu to have a role here)".

"swelling clays" include smectities, bentonites, montmorrillinites etc not necessarily related to liquifaction potential however......

Thank you for all the answers :)

very helpful

The is no relation between clayey minerals and liquifaction. This phenomena deals with loose fine sand or silty fine sand only

Ashrar.....not entirely true....Google "Rissa Landslide".....

http://www.youtube.com/watch?v=3q-qfNlEP4A

Dear Keith,

Although I could not watch the "Rissa Landslide" on YouTube, this phenomena also related with oversaturation of soils, including clayey soils as well. Soil stability is strongly related with internal friction angle and pore water pressure. Clayey soils are maybe stable in dry conditions, but they start to swelling first, than getting plastic deformation under wet conditions. Liquifaction is a physical phenomena related with pore pressure and grain size of soils. But the grain-size distribution is very variative that permit sometimes up to 15 percent clay content of sensitive soils for liquefaction. As in social relations, there are many tones of gray in the nature as well, not only black and white. Happy new year to all...

Liquefaction phenomenon is witnessed in sandy strata and not in clayey ones. Swelling and squeezing is common with montmorillonite and illite minerals.

The question posed by Ryandi Adlan relates to what he calls mudstone or claystone, therefore hardened (dry) layers which may be found on the surface or as interlayers between other rock (stone) formations. If this is the case, I think that reference to sandy soils alone as an example of liquefaction, may be misleading. On the other hand, any clay mineral, of which there is quite a veriety (motmorillonite being perhaps the most well known expandable variety) show the well known behaviour exploited by pottery makers over the millennia of human civilisation, by which the "mudstone" seems to be able to absorb a limitless amount of water, therefore going through the various stages of "hardness" through malleable, ductile, "leathery", etc, etc, and all the way to liquid. Only the firing process (baking in a very hot oven), the clay object shaped by the potter (or by the brick maker) makes the clay minerals wich made up the "mudstone" unable to absorb water any more, having transformed into other silicate minerals (mostly unhydrous) or glass. All this to say that in a natural environment, when a clay-rich layer is subject to receive a large amount of water it can surely become soft and all the way to "liquid" enhancing or triggering subsidence and /or landslide phenomena.

Clay-rich layer will not lead to liquefaction under no circumstances. But presence of clay in the joints in rockmass or in overburden (as slope forming materials) may causelandslide when wet.

Pramod - please check out video from Youtube of the "Rissa" Landslide and review your comment accordingly: http://www.youtube.com/watch?v=3q-qfNlEP4A

I have seen video of 'Rissa' landslide . It seems to be a case of landsliding due to toe- erosion or breaching of marine clay( Quick clay) deposits due to water action.

Rissa is due to loosing strength of a very sensitive marine clay which became sensitive due to removing salt from it due to rainfall infiltration and fresh groundwaterflow

The last couple of comments, as well as the earlier ones, regarding the "Rissa" landslide add to the widespread knowledge that clay sediments are prone to change their mechanical and static behaviour in response to water activity, which is what we should concentrate on. Other standpoints on the matter do not seem, in my opinion, aimed at answering the original question which was posed in fairly clear terms.

At my profile one can find several paper on liquefaction of sand with fines, full paper request by email will be answered immediately

... Liquefaction not to be mixed up with terms as liquid limit etc ;-)

Hi friends! Rissa is a typical example of thixotropy. For explanation read at least Wikipedia:"Thixotropy is shear thinning property. Certain gels or fluids that are thick (viscous) under normal conditions flow (become thin, less viscous) over time when shaken, agitated, or otherwise stressed. They then take a fixed time to return to a more viscous state. In more technical language: some non-Newtonian pseudoplastic fluids show a time-dependent change in viscosity; the longer the fluid undergoes shear stress, the lower its viscosity. A thixotropic fluid is a fluid which takes a finite time to attain equilibrium viscosity when introduced to a step change in shear rate. Some thixotropic fluids return to a gel state almost instantly, such as ketchup, and are called pseudoplastic fluids. Some clays are thixotropic, with their behavior of great importance in structural and geotechnical engineering. Landslides, such as those common in the cliffs around Lyme Regis, Dorset and in the Aberfan spoil tip disaster in Wales are evidence of this phenomenon. Drilling muds used in geotechnical applications can be thixotropic, etc.". In the engineering geology, what we call liquefaction, it is another process, really connected ony with soils of two mixed distinctive grain-size ranges, where water erosion removes fines between considerably coarser grains, leading to increasing hollow pores and underground spaces and finally to the structure collapse of the non-cohesive soil. This process is also known as suffosion. This was the reason of the Danube River dam breaking in 1967 in Slovakia. Fine sand was washed out from the gravel of the Quaternary river sediments under the dam foundation due to very high hydraulic gradient in the sediment during extremly high water table in the Danube River. This cuased a devastating flood in the region... So, in engineering geological terms, I fully agree with Mr. Pramod Nawani, liquifaction/suffosion is impossible in claystones, they are too impermeable.

Your problem, Ryandi, is the thixotropy of clays. This happens when the water content is critically high, the forces between the solid grains too low, so that any additional static or dynamic load impuls can break them and the clay will flow. In this case, not only the clay mineral type, but also the type of exchangeable ions and of the ions in the pore solution controll, if the clay is thixotropic or not. However, the most important thing is the solid:water ratio. Thixotropy occurs even in kaolin above 20% solid content in the dispersion (Lagaly, 1989: Principles of Flow of Kaolin and Bentonite Dispersions. Applied Clay Science, 4 (1989) 105-123. This could be the answer for you, if only montmorillonite...

And, be careful with the terms, subsidence is again something totally different!

As i said yesterday here and was deleted. In the meantime, i completely disagree, ...

I feel explanation given by Ms Adamcova is well acceptable.

Lyme Regis and Aberfan can not be compared - very different sorts of phenomena - Aberfan was a debris flow of saturated colliery spoil, Lyme Regis are examples of classical slip circle failures in over-consolidated clays due to toe erosion.

OK, first part was just a full citation from Wikipedia about thixotropy, including examples. I should not mention localities that I do not know exactly, my fault, sorry! I forgot about the traps of Wikipedia. However, Lagaly is a serious source!

I say it again, "thixotropy" has nothing to do with Rissa quick clay, see the attachment

If you call "liquefaction" the tendency that the effective stress path in p'-q-plot of an undrained loading turns to the left, = effective stress decreases to almost zero, then also plots in the above paper show this observation, but commonly we do not call it liquefaction but "steady stae"

Citation from that Rissa .pdf: "For a quick clay, loaded undrained beyond "tau"ef, the pore pressures will increase explosively as the unstable "card house" clay particle structure will start collapsig, resultig in a net decrease in shear strength. Consequently, failure takes place almost instantaneously and long before the angle of internal friction is ully mobilized (Aas, 1981)". It is, in other words, the same card house clay structure collapse as described by Lagaly. As you could see in the Rissa video, addition of salt, i. e. changed type and concentration of ions in the pore solution, accelerated the change from the liquid sensitive clay to the plastic consistency again. I think Lagaly and Prof.Schanz are writing about the same phenomenon, but one from the clay-mineralogical and the other one rather from the mechanical point of view. I stop, sorry, no more time. Nevertheless, the question was not Rissa, but, if another clay minerals can cause similar collapse (I don´t think that Ryandi was asking about the steady state in loading plots).