اثر وجود عدم‌قطعیت در قابلیت فشردگی خاک بر تغییرات زمانی فشار آب منفذی در پی سازه

نوع مقاله: مقاله پژوهشی

چکیده

با توجه به عدم­قطعیت و تغییرات مکانی مقادیر پارامترهای تحکیمی خاک و تاثیر آن بر فشار آب منفذی حین نشست در پی سازه­، امروزه کاربرد روش­­های احتمالاتی مبتنی بر عدم­قطعیت در تحلیل چنین مسائلی رایج می­باشد. در تحقیق حاضر، نقش عدم­قطعیت قابلیت فشردگی حجمی خاک به عنوان یکی از عوامل موثر بر تغییرات زمانی فشار آب منفذی حین تحکیم در ناحیه شفت استان گیلان مورد بررسی قرار گرفت. بدین منظور نمونه­برداری خاک از 9 گمانه (مربوط به پی یک سازه فولادی و محوطه آن واقع در حومه شهرستان شفت) انجام شد و با آزمایش تحکیم، توزیع لوگ­نرمال پارامتر قابلیت فشردگی حجمی خاک به دست آمد. سپس یک برنامه­ رایانه­ای در محیط MATLAB برای تحلیل احتمالاتی معادله دیفرانسیل تحکیم به روش مونت­کارلو توسعه داده شد. طبق نتایج، با افزایش تعداد نمونه تصادفی (ضریب قابلیت فشردگی) در روش مونت­کارلو از 100 به 1000 نمونه، تغییر قابل توجهی در نتایج مشاهده نگردید. در حالیکه کشیدگی منحنی­های چگالی احتمال با زمان، حاکی از نقش قابل توجه گذشت زمان در افزایش عدم­قطعیت فشار آب منفذی می­باشد. همچنین در یک عمق معین، ضخامت بیشتر لایه خاک مورد بررسی منجر به افزایش عدم­قطعیت نتایج گردید. با 2 برابر شدن عمق نقطه مورد بررسی و ضخامت لایه خاک، چگالی احتمال بیش از 20 برابر افزایش یافت. در نهایت بیش­ترین افزایش ضریب تغییرات فشار آب منفذی طی 100 روز در لایه خاک به ضخامت 4 متر برابر 15/2 درصد و در لایه خاک با ضخامت 16 متر کمتر از 25/0 درصد به دست آمد.

کلیدواژه‌ها


عنوان مقاله [English]

Effect of Uncertainty of Soil Compressibility on Temporal Variations of Pore-Water Pressure at the Foundation of Structure

چکیده [English]

                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               Today, as a result of the uncertainty and spatial variations of soil consolidation parameters and their effects on the pore-water pressure during the foundation settlement, it is common to apply the uncertainty-based probabilistic methods in such problems. In current study, the role of uncertainty of soil volumetric compressibility, as one of the effective factors on temporal variations of pore-water pressure during consolidation was investigated in Shaft region of Guilan province. In this respect, soil sampling was carried out in 9 bore holes (at the foundation of a steel structure and its yard located in Shaft town). Following the consolidation experiments, the log-normal distribution of soil volumetric compressibility was derived. Then, a computer code was developed in MATLAB to probabilistically analyze the partial differential equation of consolidation using Monte-Carlo simulation method. According to the results, increasing the number of random samples (of compressibility coefficient) from 100 to 1000 caused negligible effects. Whereas, the widening of probability density curves with time implies the dramatic effect of time on increasing the uncertainty of pore-water pressure. Meanwhile, for a given depth, the increased thickness of investigated soil layer caused greater uncertainty of pore-water pressure. Doubling the soil depth and investigated thickness of soil layer led to the increase of probability density by more than 20 times. Finally, during 100 days, the greatest temporal increase in coefficient of variation of pore-water pressure was obtained equal to 2.15 and 0.25 percent for 4- and 16-meters thick layers of soil, respectively.      

کلیدواژه‌ها [English]

  • Consolidation settlement of soil
  • Log-normal distribution
  • Monte-Carlo method
  • Probabilistic analysis
  • Soil sampling
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