تعیین زمان تکمیل ‌واکنش تحت شرایط متفاوت دمایی دربهسازی خاک های ماسه ای به روش سیمانتاسیون بیولوژیکی

خواص مکانیکی خاک‌ها اغلب انتظارهای بشر را برآورده نمی‌سازند، به همین دلیل روش‌های بهسازی متفاوتی بررسی شده است. روش رسوب میکروبی کلسیت، روشی نوظهور است؛ که با استفاده از میکروارگانیسم‌های موجود در خاک و فرایندهای شیمیایی و تولید رسوب کلسیت، سبب بهبود خواص مکانیکی خاک شده است. همچنین روشی کم‌هزینه و سازگار با محیط زیست است. اما نکته‌یی که در عمده‌ی پژوهش‌های اخیر به آن توجه نشده است، بررسی آثار پارامترهایی، مانند: شرایط دمایی، غلظت مواد و غلظت باکتری متفاوت به صورت همزمان بوده است. در مطالعه‌ی حاضر از باکتری باسیلوس پاستوری در خاک ماسه‌یی استفاده شده است. نتایج نشان می‌دهند که پارامترهای مذکور تاثیر قابل توجهی در زمان تکمیل واکنش در شرایط متفاوت دارند. همچنین میزان تاثیر هر یک از آن‌ها (دما، غلظت باکتری و غلظت مواد) بررسی شده است.

Determination of the role of retention time under different temperature conditions In the improvement of sandy soils by biocementation

The mechanical properties of soils often do not fulfill human needs and expectations due to world population growth. Preventing damage to buildings and infrastructures requires basic measures or ongoing maintenance. For this issue, construction of any structure needs to be on a good soil bed with favorable strength parameters. So far, some improvement methods have been studied and applied. In geotechnical engineering, finding a lowcost and environmentally friendly method is the most improvement challenging problem. Microbial geotechnology is a new branch of geotechnical engineering that deals with the microbiological applications. Microbial sedimentation method (MICP) is a new and emerging method that uses microorganisms in the soil and chemical processes and, thus, the production of calcite sediment increases shear strength and hardness as well as reduces permeability. In this research, we focus on microbial catalysis of urea hydrolysis, which has led to the deposition of calcium carbonate in sand using Bacillus Pasteurii. However, recent researches have not addressed the effects of some parameters such as temperature and material concentration and various bacterial concentrations simultaneously. In this study, under different temperature conditions, different material concentrations, and different bacterial concentrations (different ODs), the reaction completion time is obtained. Significant experimental results show that OD changes have little effect on the result. Also, it is demonstrated that by increasing temperature, the amount of calcium carbonate deposits has also increased. Moreover, the higher the concentration of the material raises, the greater the amount of calcium carbonate deposits, making its formation faster. Also, samples with higher concentrations need a longer time to complete their reaction. Hightemperature samples have a higher reaction rate from the earliest hours, but lowtemperature samples require more time to precipitate calcium carbonate. Also, with the help of electron scanning, the effect of material concentration on the way of connection bonding and bonding between particles has been investigated.