نوع مقاله: مقاله پژوهشی

نویسندگان

1 دانشجوی کارشناسی ارشد سازه‌های آبی گروه مهندسی آب دانشگاه رازی

2 استادیار گروه مهندسی آب دانشگاه رازی

10.22055/jise.2017.20416.1468

چکیده

بررسی جریان آب در خاک‌های اشباع و غیر‌اشباع به‌منظور تعیین دبی نشت، فشار آب منفذی، نیروی بالابرنده و گرادیان هیدرولیکی در طراحی سدها مورد توجه متخصصین است. شبیه‌سازی عددی یک روش سریع و کم‌هزینه برای مطالعه حرکت آب در محیط متخلخل است که در دهه‌های اخیر رشد چشم‌گیری داشته است. در این تحقیق، معادله ریچاردز در حالت دو بعدی و غیرماندگار با استفاده از روش عـددی حجم محدود و شبکه‌بندی نامنظم مثلثی جداسازی و یک مدل کامپیوتری تهیه شد که قابلیت شبیه‌سـازی حرکت آب در خاک اشـباع و غیراشـباع را دارد. در این مدل به‌منظور محاسبه هدایت هیدرولیکی در محیط غیراشباع برای شبیه‌سازی جریان می‌توان از رابطه ون‌گنوختن و یا توابع دیگر استفاده کرد. مدل عددی در دو بخش جریان محصور و غیرمحصور با داده‌های آزمایشگاهی سایر پژوهشگران صحت‌سنجی شد. متوسط خطای مدل عددی در محاسبه فشار در جریان محصور و غیرمحصور به‌ترتیب 1/1 و 5/1 درصد و متوسط خطای آن در محاسبه دبی نشت در جریان غیرمحصور 6/5 درصد است، که دقت مناسبی برای مدل عددی است. یکی از موارد بسیار مهم در کنترل پایداری سدهای خاکی، میزان فشار آب منفذی و نیروی نشت ایجاد‌شده در شرایط وقوع افت ناگهانی سطح آب در مخزن است. متوسط درصد خطای محاسبه فشار آب منفذی در شرایط نشت غیرماندگار توسط مدل عددی 6/5 درصد است. در شرایط افت ناگهانی سطح آب، توزیع فشار در جریان غیرماندگار در بخش‌های بالادست از حالت هیدرواستاتیک مقداری خارج شده و باعث اختلاف فشار آب منفذی محاسباتی و مشاهداتی می‌شود.

کلیدواژه‌ها

موضوعات

عنوان مقاله [English]

Modeling Seepage in Porous Media Using an Unstructured Triangular Finite Volume Algorithm

نویسندگان [English]

  • Elham Fazeli 1
  • Mohammad Mehdi Heidari 2

1 M. Sc. student, Department of Water Engineering, College of Agriculture and Natural Resources, Razi University.

2 Assistant Professor, Department of Water Engineering, College of Agriculture and Natural Resources, Razi University

چکیده [English]

The explorers consider the study of water flow in saturated and unsaturated soils to determine the seepage, pore pressure, uplift force, and hydraulic gradient in the design of dams. Numerical simulation is a rapid low-cost method for the study of soil water flow, which has recently been increased. Many investigators have described approximate methods, based on Dupuit assumptions, to locate the surface of seepage and seepage discharge for different tailwater positions. In order to reduce the seepage discharge and, consequently, flow energy reduction passing the dam, various actions such as the construction of clay core, trench and grout certain, and clay cover on the reservoir floor have been considered. Despite all the measures taken to prevent the movement of water in the embankment dam, water always penetrates the downstream parts due to the permeability of the materials. Drainage systems are designed to collect and direct seepage of water to downstream areas, keeping the dam’s riffle slope dry to decrease the hydroscopic pressure and increase the stability of the embankment dams. Horizontal drains are widely used in homogeneous embankment dams with an average height. In this study, Richards equation was desecrated in two-dimensional and unsteady conditions using an unstructured triangular finite volume algorithm and a computer model developed to simulate seepage in saturated-unsaturated soils. In this model, Van Genuchten equation or other functions can be used to calculate hydraulic conductivity in unsaturated soil for the simulation of flow.

کلیدواژه‌ها [English]

  • Earth dam
  • Phreatic line
  • Soil water flow
  • Van Genuchten equation
  • Numerical simulation

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