Well

Mainly the dissociation(dissolution) process.

Regards

Dear Mr. Moghadam,

I do not know what kind of sample you speak about; is it soil or rock? This is a different story. What I can decipher seems to me as a junk of marly claystone or clayish marlstone. Irrespective of the precise mineralogical composition the rock contains calcareous parts (calcite and/or dolomite) and as second component the clay minerals, in this case micaceous and/or smectite group minerals to categorize it in this way as marlstone. The composition of these phyllosilicates is crucial because both clay mineral groups respond in a different way to fluids like water. The expandability of smectite group minerals causes what is called heave and as such the amount and composition of these smectite-group clay minerals have a strong impact on the destabilization of the rock. As long as no precise mineralogy is on the table any more far-reaching discussion is impossible.

Kind regards H.G.Dill

Dear Mr. Moghadam,

the explanation by Mr. Dill is helpful but there are some other factors to consider.

For some weak rocks it is typical that they disintegrate in contact with water. I conducted some research on a similar material (Emscher Marl) with a similar result. Did you dry your specimen before immersing them with water or did you try to test them with their in situ water content?

When the specimen was dried before the contact with water it is possible that a softening process occured observable by small, ascending gas bubbles called pore air compression. So perhaps your desintegration process may be a physical one, not a chemical one.

You can read something about desintegration mechanisms in my conference paper in the section "desintegration mechanisms".

You can find it here:

Conference Paper Evaluation of effective strength parameters in mudrocks

Best regards

Christian Ungewitter