بهینه‌سازی مقاومت ماسه بهسازی شده بیولوزیکی توسط روش سطح پاسخ

نوع مقاله : علمی - پژوهشی

نویسندگان

1 دانشجوی دکتری ژئوتکنیک ، گروه مهندسی عمران، واحد قزوین، دانشگاه آزاد اسلامی، قزوین، ایران

2 دانشیار، گروه مهندسی عمران، واحد قزوین، دانشگاه آزاد اسلامی، قزوین، ایران

3 استادیار، گروه مهندسی عمران، واحد قزوین، دانشگاه آزاد اسلامی، قزوین، ایران

چکیده

نیاز به افزایش زیرساخت های شهری و عدم دستیابی به خاک با کیفیت مناسب ، باعث افزایش تقاضا برای روش های جدید جهت بهسازی خاک گردید. اخیراً، بهسازی پارامترهای مقاومت، سختی و نفوذپذیری ماسه تحت رسوب بیولوژیکی کربنات کلسیم به عنوان روش های نوآورانه و سازگار با محیط زیست بسیار مورد توجه متخصصان ژئوتکنیک قرار گرفته است. بنابراین بررسی پارامترهای موثر بر تکنیک بهسازی بیولوژیکی و یافتن ترکیب ایده‌ال در جهت افزایش کارایی و کاهش هزینه ها بسیار حائز اهمیت می باشد. هدف اصلی مقاله، بررسی اثر متغیرهای مولاریته محلول سیمانتاسیون، چگالی اپتیکی باکتری و زمان عمل آوری نمونه ( هرکدام با سه سطح تغییرات) بر روی پارامترهای تنش های انحرافی و موثر برای ماسه بهسازی شده بیولوژیکی تحت آزمایش سه محوری زهکشی نشده بود. ماسه مورد استفاده در این پژوهش از نوع ماسه بددانه بندی شده و باکتری ها از نوع اسپروسارسینای پاستوری با فعالیت اوره‌آزی مثبت بود. جهت بهینه نمودن پارامترهای تنش در ماسه بهسازی شده و همچنین کاهش قابل توجه تعداد آزمایشات از روش سطح پاسخ استفاده گردید. طرح مورد استفاده در روش سطح پاسخ، طرح باکس بنکن با پنج نقطه مرکزی بود. جهت ارزیابی و مقایسه میزان تاثیر هر یک از متغیرها از نمودارهای سه بعدی و کانتورهای مدل رگرسیونی استفاده شد. در این روش مطابق آنالیز واریانس برای داده ها، تاثیر تمامی متغیر ها بر پاسخ ها معنادار بوده و مقادیر بهینه برای تنش های موثر و انحرافی به ترتیب 2/958و 4/1032 (kPa) بدست آمدند. مشاهدات نشان داد که باتوجه به شیب نمودار و کانتورها، مولاریته محلول سیمانتاسیون بیشترین تاثیر را بر پاسخ ها داشته و تاثیر چگالی اپتیکی باکتری بر تنش موثر نسبت به تنش انحرافی، کمتر بود که می‌تواند به دلیل تجمع باکتری های مازاد ( عدم وجود مواد مغذی کافی ) و تاثیر آن بر فشار آب منفذی اضافی باشد.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Optimization of resistance of biologically improved sand by response surface methodology

نویسندگان [English]

  • Seyed Abdollah Ekramirad 1
  • Mohammad Azadi 2
  • Naser Shamskia 3
1 Ph.D Student of Geotechnical engineering, Department of Civil Engineering, Qazvin Branch, Islamic Azad University, Qazvin, Iran
2 Associate Prof., Department of Civil Engineering, Qazvin Branch, Islamic Azad University, Qazvin, Iran
3 Assistant Prof., Department of Civil Engineering, Qazvin Branch, Islamic Azad University, Qazvin, Iran
چکیده [English]

Need to increase urban infrastructure and lack of access to suitable quality soil increased demand for new methods for soil improvement. Recently, improving the parameters of strength, stiffness and permeability of sand under microbial induced calcite precipitation has received much attention from geotechnical experts as innovative and environmentally friendly methods. Therefore, it is very important to study the parameters affecting the biological improvement technique and find the ideal combination to increase efficiency and reduce costs. The main purpose of this paper is to investigate the effect of the variability of cementation solution molarity, bacterial optical density and curing time (three levels of variation for each) on the parameters of deviation and effective stresses for biologically improved sand under undrained triaxial compression test. The sand used in this study is a SP soil according to the unified soil classification system, and the adopted micro-organism is Bacillus pasteurii as the urease-positive bacterium. The response surface methodology was used to optimize the stress parameters in the improved sand and to significantly reduce the number of experiments. The experiments were designed using a Box-Behnken design with five central points. Three-dimensional schemes and regression model contours were used to evaluate and compare the effect of each variable. In this method, according to the analysis of variance for the data, the effect of all variables on the responses was significant and the optimal values for effective and deviation stresses were 958.2 and 1032.4 (kPa), respectively. Due to the slope of the curves, the molarity of the cementation solution had the greatest effect on the responses, and the effect of bacterial optical density on effective stress was less than deviation stress, that may be due to the accumulation of excess bacteria (lack of nutrients) and its impact on excess pore water pressure.

کلیدواژه‌ها [English]

  • Biological improvement
  • Cementation solution molarity
  • Optical density
  • Curing time
  • RSM
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