ﺗﺄﺛﯿﺮ ﻫﯿﺪراﺗﺎﺳﯿﻮن اوﻟﯿﻪ ﺑﻨﺘﻮﻧﯿﺖ ﺑﺮ ﺗﻐﯿﯿﺮ ﺧﺼﻮﺻﯿﺎت ﺧﻤﯿﺮي آن در اﻧﺪرﮐﻨﺶ ﺑﺎ آﻻﯾﻨﺪه آﻟﯽ

Impact of Initial Hydration of Bentonite on Its Plasticity Properties Change in Interaction with Organic Contaminant

زﻣﯿﻨﻪ و ﻫﺪف: آﺳﺘﺮ ﺧـﺎك رﺳﯽ ﻣﺘـﺮاﮐﻢ )CCLs( ﺑﻪ دﻟﯿــﻞ ﺿﺮﯾﺐ ﻧﻔـﻮذﭘﺬﯾﺮي ﮐﻢ و ﻗـﺎﺑﻠﯿﺖ ﻣﻨﺎﺳﺐ در ﺟـﺬب و ﻧﮕــﻬﺪاري آﻻﯾﻨــﺪه، در ﻣﺮاﮐـﺰ دﻓﻦ ﻣﻬﻨﺪﺳﯽ زﺑﺎﻟـﻪ ﻣﻮرد اﺳﺘﻔـﺎده ﻗﺮار ﻣﯽﮔﯿﺮد. ﺗﻐﯿﯿﺮ وﯾﮋﮔﯽﻫﺎي ﺳﯿـﺎل ﻣﻨﻔﺬي در ﺧﺎك، ﺗــﺄﺛﯿﺮ ﺑﺴﺰاﯾﯽ ﺑﺮ ﻣﺸﺨﺼﺎت ﻣﻬﻨﺪﺳﯽ و رﻓﺘــﺎري ﺧﺎكﻫﺎي رﺳﯽ دارد. ﺑﺎ وﺟﻮد ﺗﺤﻘﯿﻘﺎﺗﯽ ﮐﻪ در ﺧﺼﻮص ﻓﺮآﯾﻨﺪ اﻧﺪرﮐﻨﺶ رس و ﻣــﻮاد آﻟﯽ ﺻﻮرت ﮔﺮﻓﺘـﻪ، در زﻣﯿﻨﻪ ﺗﺄﺛﯿـﺮ ﻫﯿﺪراﺗﺎﺳﯿﻮن اوﻟﯿﻪ ﺑﻨﺘﻮﻧﯿﺖ و ﺗﻐﯿﯿــﺮ در ﺛﺎﺑﺖ دياﻟﮑﺘﺮﯾﮏ آﻻﯾﻨﺪه آﻟﯽ ﺑﺮ ﺧﺼﻮﺻﯿــﺎت ژﺋﻮﺗﮑﻨﯿﮑﯽ و ژﺋﻮﺗﮑﻨﯿﮏ زﯾﺴﺖ ﻣﺤﯿﻄﯽ ﺑﻨﺘﻮﻧﯿﺖ ﺗﺤﻘﯿﻘـﺎت ﻣﺤﺪودي اﻧﺠﺎم ﺷﺪه اﺳﺖ. در ﺣﺎﻟﯽ ﮐﻪ ﭼﻨﯿﻦ ﻓﺮآﯾﻨﺪ اﻧﺪرﮐﻨﺸﯽ در ﺑﺴﯿـﺎري از ﭘﺮوژه ﻫـﺎي ﺻﻨﻌﺘﯽ و دﻓﻦ ﻣﻬﻨﺪﺳـﯽ زﺑﺎﻟﻪ ﺑﻪ ﻋﻨﻮان ﯾﮏ ﻋﻤﻠﮑﺮد ﻣﻮرد اﻧﺘﻈﺎر ﺑﻪ وﻓﻮر رخ ﻣﯽدﻫﺪ. روش ﺑﺮرﺳﯽ: در اﯾﻦ ﺗﺤﻘﯿﻖ از ﺧـﺎك ﺳﺪﯾﻢ-ﺑﻨﺘﻮﻧﯿﺖ در ﻣﻌﺮض 2 ﻧﻮع ﻣـﺎده آﻟﯽ )اﺗـﺎﻧﻮل و اﺳﯿـﺪ اﺳﺘﯿﮏ( ﺑـﺎ ﺛـﺎﺑﺖ دياﻟﮑﺘﺮﯾﮏ ﻣﺨﺘﻠﻒ ﺗﺤﺖ ﺷـﺮاﯾﻂ ﻫﯿـﺪراﺗـﺎﺳﯿﻮﻧﯽ ﻣﺘﻔـﺎوت اﺳﺘﻔـﺎده ﺷـﺪه اﺳﺖ. ﭘﺲ از ﺣﺼـﻮل ﺗﻌـﺎدل، ﺗـﺄﺛﯿـﺮ ﻓﺮآﯾﻨـﺪ ﻫﯿـﺪراﺗـﺎﺳﯿﻮن اوﻟﯿـﻪ و ﻫﻤﭽﻨﯿﻦ ﺗﻐﯿﯿـﺮ در ﺛـﺎﺑﺖ دي اﻟﮑﺘﺮﯾﮏ ﺑﺮ ﺧﺼﻮﺻﯿﺎت ﺧﻤﯿﺮي ﺑﻨﺘﻮﻧﯿﺖ در اﻧﺪرﮐﻨﺶ ﺑﺎ ﻣﻮاد آﻟﯽ ﺗﻮﺳﻂ آزﻣﺎﯾﺶ ﺣﺪود اﺗﺮﺑﺮگ ﻣﻮرد ﺑﺮرﺳﯽ آزﻣﺎﯾﺸﮕﺎﻫﯽ ﻗﺮارﮔﺮﻓﺘﻪ اﺳﺖ. ﯾﺎﻓﺘﻪ ﻫﺎ: ﻧﺘـﺎﯾﺞ ﺣـﺎﮐﯽ از آن اﺳﺖ ﮐـﻪ در ﻧﻤـﻮدار ﺧﻤﯿـﺮي ﮐﺎﺳـﺎﮔﺮاﻧﺪه، ﻧﻤﻮﻧـﻪ ﻫﺎي ﺳﺪﯾﻢ-ﺑﻨﺘﻮﻧﯿﺖ ﺑـﺎ ﻫﯿﺪراﺗـﺎﺳﯿﻮن اوﻟﯿـﻪ و ﻗـﺮار ﮔﺮﻓﺘـﻪ در ﻣﻌﺮض اﺗﺎﻧﻮل و اﺳﯿﺪ اﺳﺘﯿﮏ ﺑﻪ ﺗﺮﺗﯿﺐ، ﻫﻤﭽﻨﺎن ﺑﻪ ﻋﻨﻮان ﺧﺎك CH و اﻧﺘﻘﺎل ﯾﺎﻓﺘﻪ از ﻧﺎﺣﯿﻪ CH ﺑﻪ MH ﻃﺒﻘﻪ ﺑﻨﺪي ﺷﺪه اﻧﺪ. ﻧﺘﯿﺠﻪﮔﯿﺮي: ﺗﻐﯿﯿﺮ در ﺛﺎﺑﺖ دياﻟﮑﺘﺮﯾﮏ و ﺷﺮاﯾﻂ ﻣﺘﻔﺎوت ﻫﯿﺪراﺗﺎﺳﯿﻮﻧﯽ ﻣﻨﺠـﺮ ﺑﻪ ﺗﻐﯿﯿـﺮ در ﺿﺨﺎﻣﺖ ﻻﯾﻪ دوﮔﺎﻧﻪ ﺷﺪه اﺳﺖ ﮐﻪ اﯾﻦ ﻋﺎﻣﻞ، ﻣﻮﺟﺐ ﺗﻐﯿﯿﺮات ﻗـﺎﺑﻞ ﺗﻮﺟﻬﯽ در ﺳﺎﺧﺘﺎر و ﺗﻐﯿﯿﺮ رﻓﺘﺎر ﺧﺎك رﺳﯽ ﺷﺪه اﺳﺖ. اﯾﻦ ﺗﻐﯿﯿﺮات ﺑﺮ اﺳﺎس رواﺑﻂ ﺗﺌﻮرﯾﮏ ﻣﻮﺟﻮد ﻣﻮرد ﺗﺠﺰﯾﻪ و ﺗﺤﻠﯿﻞ ﻗﺮار ﮔﺮﻓﺘﻪ و ﻣﺤـﺪودﯾﺖﻫﺎي ﻧﻈﺮي در رواﺑﻂ ﺗﺌـﻮرﯾﮏ در ﺗﻔﺴﯿـﺮ ﭘـﺎﺳﺦﻫﺎي ﺧـﺎك ﺑﻪ ﺗﻔﮑﯿـﮏ ﺑﺤﺚ ﺷﺪهاﻧﺪ.

Background and Objective: The compacted clay liners (CCLs) due to their low permeability and suitable capability for contaminant retention are widely used in engineering waste disposal sites. Generally, the change in properties of soil pore fluid has a very distinguished impact on the behaviour of clayey soils. In spite of several researches, which have been performed on the process of clay and organic contaminant interaction, there are few researches on the influence of dielectric constant of organic contaminant and initial hydration of bentonite on the geotechnical and geo-environmental properties of organic contaminated bentonite. Such a process is very common in many industrial and waste disposal projects. Methods: This research was performed on sodium-bentonite soil samples which were exposed to two different organic materials (Ethanol and Acetic Acid) which have different dielectric constant. Furthermore, two different pre-hydration and post-hydration conditions were studied in this research. After achieving equilibrium condition, the influence of initial hydration and change on the dielectric constant of pore fluid upon interaction of organic material and bentonite was investigated. The investigation focuses attention on the plasticity properties of bentonite by the use of Atterberg limit tests. Findings: The achieved results indicate that in Casagrande's plasticity chart, two pre-hydrated sodium-bentonite soil samples which were exposed further to ethanol and acetic acid are classified as CH and shifted from CH to MH, respectively. Discussion and Conclusion: The change on the dielectric constant of pore fluid and different hydration conditions cause a change on the thickness of the double layer of clay fraction of the soil. This causes a noticeable change on the structure and behaviour of clay fraction of the soil sample. This variation on bentonite behaviour has been discussed based on the current available theory of double layer. Furthermore, the theoretical limitation for interpretation of results has been addressed.