What is the effect of the Gypsum percentage on the collapse potential of the soil?
The collapse potential (CP) of the soil can be calculated by the Single Oedometer Test or Double Oedometer Test.
The collapse potential increases when the gypsum content increases in both tests ; the single and double oedometer tests
The collapsibility of the soil can be estimated from the term (collapse potential-CP) which can be obtained from two types of tests performed in the odometer device:(1) Single Oedometer Test (SCT) and (2) Double Odometer Test (DOT).
Dear Prof. Dr. Hasan
Thanks a lot for your valuable answer and useful information.
I agree with you.
Do you think that the increases in Gypsum content in soil sample will cause an increase or decrease the collapse potential during the collapse test?
Best regards
Qasim
Generally, Increasing of gypsum content leads to increase the collapse potential of soil due to increase the solubility of gypsum in the soil. the severity of collapse depends on the solubility of gypsum, which depending on the many conditions such as gypsum type, temperature, type of water etc...
Dear Dr. Qasim,
Collapse-ability is two folds:
(1) Material related.
(2) Loading/functional conditions related.
I. Material related
(1) The density of the basic element of the soil and the stability of its mineralogy.
(2) At a given soil type and density, it depends on the percentage (%) of cementing agent (gypsum), and slightly on its initial moisture content.
(3) At the given mineralogy, density and gypsum percentage, the homogeneity and the isotropy of the soil as well as the uniformity of the gypsum distribution are also factors. (Have considerable uncertainty though)
II. Loading/functional conditions
(1) The salinity of the water, which, in your case, is supposed to be controlled.
(2) The mode of application of water.
(3) The weight of gypsum to the weight of the saturation water.
III. Conclusion
(1) From all of the above, and keeping other factors stationary, the high percentage of gypsum gives rise to more mobilized collapse, as long as the void ratio is large enough to accommodate adequate amount of water to dissolve the gypsum.
(2) If the amount of water is not adequate to dissolve all the gypsum, the larger gypsum % will result in a better stability and less collapse settlement.
(3) If the soil matrix is subject to flowing water, the solubility issue will not govern, and the low gypsum% sample/formation will give larger settlement on the shorter term, while the high gypsum% sample/formation will exhibit larger settlement of the long run.
IV. Limitation
I would like to also mention that the problem has linearity, which depends on the magnitude of the difference between the analyzed gypsum%, due to the variation of the test matrix composition in the background.
Kindest regards,
Hesham Elshazly
Dear Dr. Qasim,
In the limitations part of my answer above, the 'linearity' is a typo. I meant 'non-linearity'.
Also 'of the long run' is actually 'on the long run'
Sorry if these typos may have caused any confusion.
Kind regards,
Hesham Elshazly
Dear Prof. Hesham Elshazly
Thanks a lot for your detailed, very specific and scientific answer.
I like your classification for the collapse mechanism and deformation strategy.
Actually the high amount of Gypsum content may not lead to further collapse deformation especially when wetting under soaking condition.
I agree with you, follow of water through the soil mass by (Leaching Phenomenon) can be introduced a sever collapse deformation due to more dissolution of gypsum particles.
Regards
Qasim
Thank you Prof. Qasim for your generous remark.
Kindest regards,
Hesham Elshazly
The collapse potential increases with increasing gypsum content. This is due to dissolution gypsum during soaking
Dear Dr. Mohammed Abdullateef Al-Neami
Dear Dr. Shaimaa Fadhil
Thanks for your useful comments.
Do you think this behavior is expected for any percentage of gypsum or there is a specified limit after that a decrease in CP may occur?
Regards.
Qasim
Dear Mr. Najam Wani
Thanks a lot for your valuable answer and support.
Regards
Qasim
Dear Mr. Hassan Obaid Abbas
Thanks for your useful comment.
Do you think this behavior is expected for any percentage of gypsum or there is a specified limit after that a decrease in CP may occur?
Regards.
Qasim
Dear Dr. Qasim Abdulkarem Al-Obaidi
The increases in Gypsum content in the soil will increase the collapse potential CP up to optimum value. High amount of Gypsum of more than 80% in the soil may not dissolve any more by water due to the closing of all voids.
Regards
Ali
Dear Mr. Ali Al-Shamoosi
Thanks for your very important answer.
I agree with you and I should add that the type of cementation bonds between particles can play a big role in the amount of collapse deformation.
Regards.
Qasim
Dear Dr. Qasim Abdulkarem Al-Obaidi
The increase in Gypsum content in clay soil shows an increase in collapse test to 50% while an increase about 80% in leaching - collapse test.
Dear Dr. Ammar Sheikha
Thanks a lot for your answer. Are you mean increasing of collapse potential (Cp) with the increase in gypsum content? if yes why?
I would be thankful for more explanation.
Regards
Qasim
OC (Cp), in the 1st test, collapse occurs in one stage as a result of gypsum dissolving but at the 2nd test , the collapse occurs due to dissolving and washing out fine particles which leads to a fluctuation in soil skeleton and permeability throughout 3 stages, in general the final permeability increasing for high gypsum content and decreasing with low gypsum content.
Dear Dr. Ammar Sheikha and Mr. Ahmed Raad
Thanks a lot for your valuable answers.
Regards
Qasim
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