ارزیابی تغییرات ریزساختاری و پارامترهای مقاومتی ماسه‌های سیلتی تثبیت شده با نانو کلوئید سیلیکا

نوع مقاله : مقاله کامل پژوهشی

نویسندگان

دانشکده مهندسی عمران، دانشگاه تبریز

چکیده

به منظور بررسی رفتار ماسه­های سیلتی تثبیت شده با نانو کلوئید سیلیکا، 32 نمونه، تحت آزمایش مقاومت فشاری محدود نشده قرار گرفته و ریزساختار تعدادی نمونه، توسط میکروسکوپ الکترونی روبشی (SEM) بررسی شده است. نمونه­های آزمایش مقاومت تک­محوری، شامل مخلوط ماسه و مقادیر صفر، 10، 20 و 30 درصدی سیلت بوده و به روش رسوب­گذاری در محلول­های کلوئید سیلیکا با غلظت 5، 10 و 15 درصد وزنی، تهیه شده­اند. دوره عمل­آوری نمونه­ها نیز، 3 تا 30 روز در نظر گرفته شده است. با وجود این که در شرایط طبیعی، ماسه­ها و سیلت­ ها فاقد چسبندگی و مقاومت فشاری محدود نشده می­باشند، ولی مقاومت فشاری نمونه­های مختلف تثبیت شده آن­ها، در محدوده قابل توجه 25 تا 240 کیلوپاسکال قرار می­گیرد. ملاحظه می­شود در تمامی شرایط متفاوت تثبیت، بین افزایش مقاومت فشاری نمونه­ها با افزایش غلظت کلوئید سیلیکا و افزایش طول مدت عمل­آوری، رابطه­ای خطی برقرار است. اگر چه با کاهش زمان گیرش کلوئید، از شدت تأثیر زمان عمل­آوری، کاسته می­شود. همچنین در شرایط یکسان تثبیت، نمونه­های ماسه سیلتی با 10 درصد سیلت، بیشترین مقاومت فشاری را در بین دیگر نمونه­ها دارند. از طرفی دیگر، تفاوت شکل و سطوح ذرات ماسه -سیلت طبیعی و تثبیت شده، توسط تصاویر میکروسکوپ الکترونی روبشی به وضوح آشکار می­گردد، به طوری که مشخص می­شود سطح ذرات تثبیت شده، دارای توده­های لایه­ای از کلوئید سیلیکا می­باشند.

کلیدواژه‌ها

عنوان مقاله [English]

Evaluation of Effective Strength Parameters and Micro Structural Variations of Silty Sands Stabilized with Nano Colloidal Silica

نویسندگان [English]

  • Gholam Moradi
  • Shiva Seyedi
Faculty of Civil Engineering, University of Tabriz
چکیده [English]

Saturated deposits of sands and silty sands are liquefiable during earthquakes. One of the new methods proposed for non-disruptive mitigation of liquefaction risk at developed sites is passive site stabilization. It involves slow injection of colloidal silica at the edge of a site and delivery of the stabilizer to the target location using natural groundwater flow [1]. Colloidal silica is an aqueous suspension of microscopic silica (SiO2) particles produced from saturated solutions of silicic acid [2]. The particles size can range in size from 2 to 100 nm, although the particle size is fairly constant in a given suspension. During manufacturing, colloidal silica solutions are stabilized against gelation so they can have long induction periods during which the viscosity remains fairly low up to a few months. A few studies have investigated the behavior of sands stabilized with colloidal silica. Persoff et al. measured short term strength of about 430 kPa at concentration of 20 wt% colloidal silica [3]. Gallagher and Mitchell found the baseline unconfined compressive strength ranged from 32 to 222 kPa in period of 7-30 days at sands samples treated with 5-20 wt% colloidal silica. They also did a series of cyclic triaxial tests and found that for passive site remediation, a 5 wt% concentration of colloidal silica is expected to be able to adequately mitigate the liquefaction risk of loose sands [4]. The stabilization of loose silty sand with colloidal silica has not been studied comprehensively so the present study was undertaken to investigate the unconfined compressive strength and microstructure analysis of silty sands stabilized with colloidal silica.

کلیدواژه‌ها [English]

  • Unconfined compressive test
  • Silty sand
  • Colloidal silica
  • Concentration
  • Curing
  • SEM analysis

مراجع

[1]      Gallagher, P. M., "Passive Site Remediation for Mitigation of Liquefaction Risk", PhD Thesis, Virginia Polytechnic Institute and State University, Blacksburg, US, 2000.
[2]      Iler, R. K., "The Chemistry of Silica: Solubility, Polymerization Colloid and Surface Properties, and Biochemist Try", Wiley, New York, 1979.
[3]      Whang, J. M., "Chemical Based Barrier Materials", In Assessment of Barrier Containment Technologies for Environmental Remediation Applications, Rumer R. R., Mitchel J. K., Editors, Section 9, Springfield, VA: National Technical Information Service, US, 1995.
[4]   Yonekura, R., Miwa, M., "Fundamental Properties of Sodium Silicate Based Grout", 11th Southeast Asia Geotechnical Conference, Singapore, 4-8 May, 1993, pp 439-444.
[5]    Gallagher, P. M., Koch, A. J., "Model Testing of Passive Site Stabilization: A New Technique", 3rd International Conference on Grouting and Ground Treatment, US, 10-12 February, 2003, pp 1478-1489.
[6]    Gallagher, P. M., Finstere, S., "Physical and Numerical Model of Colloidal Silica Injection for Passive Site Stabilization", Vadose Zone Journal, 2004, 3 (3), 917-925.
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[8]    Hamderi, M., "Pilot Scale Modeling of Colloidal Silica Delivery to Liquefiable Sand", PhD Thesis, Drexel University, US, 2010.
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[17]   Gallagher, P. M., Mitchell, J. K., "Influence of Colloidal Silica Grout on Liquefaction Potential and Cyclic Undrained Behavior of Loose Sand", Soil Dynamics and Earthquake Engineering, 2002, 22, 1017-1026.
[18]   Towhata, I., Kabashima, Y., "Mitigation of Seismically-Induced Deformation of Loose Sandy Foundation by Uniform Permeation Grouting", 15th International Conference of Soil Mechanics and Geotechnical Engineering, Turkey, 25 August, 2001, pp 313-318.
[19]    Diaz-Rodriguez, J. A., Antonio-Izarras, V. M., Bandini, P., Lopez-Molina, J. A., "Cyclic Strength of Natural Liquefiable Sand Stabilized with Colloidal Silica Grout", Canadian Geotechnical Journal, 2008, 45 (10), 1345-1355.
[20]    Liao, H. J., Huang, C. C., Chao, B. S.,
"Liquefaction Resistance of a Colloidal Silica Grouted Sand", Grouting and Grout and Deep Mixing Third International Conference, New Orleans, US, 2003, pp 1305-1313.
[21]   Rodriguez, J. A., Izarras V. M., "Mitigation of Liquefaction Risk Using Colloidal Silica Stabilizer", 13th World Conference on Earthquake Engineering, Canada, 1-6 August, 2004, pp 509-519.
[22]   Helland, P. E., Huang, P. H., Diffendal, R. F., "SEM Analysis of Quartz Sand Grain Surface Textures Indicates Alluvial/Colluvial Origin of the Quaternary Glacial Boulder Clays at Huangshan (Yellow Mountain), East-Central China", Quaternary Research, 1997, 48 (2), 177-186.
 
نشریه مهندسی عمران و محیط زیست دانشگاه تبریز
دوره 46.4، شماره 85 - شماره پیاپی 85
زمستان 95
اسفند 1395
صفحه 77-88

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