مقایسه روش‎های فرکتالی و رزتا در تخمین منحنی رطوبتی خاک

نوع مقاله : مقاله پژوهشی

نویسندگان

1 دانشجوی دکتری گروه مهندسی علوم خاک، دانشگاه تهران

2 2- دانشجوی دکتری گروه علوم خاک، دانشگاه تبریز

3 دانشیار گروه علوم خاک، دانشگاه گیلان

چکیده

مدل ونگنوختن اغلب برای توصیف منحنی رطوبتی خاک‎ استفاده می‎شود. هدف از این تحقیق، ارزیابی روشی برای تعیین پارامترهای m و α مدل ونگنوختن برای 100 نمونه خاک از استان گیلان با استفاده از بعد فرکتال منحنی رطوبتی است. دو روش که توسط لینهارد و همکاران و ونگنوختن برای تخمین m از شاخص توزیع اندازه منافذ مدل بروکز و کوری پیشنهاد شده بود، به‎کار رفت. در هر دو روش از رابطه بین شاخص توزیع اندازه منافذ مدل بروکز و کوری و بعد فرکتال منحنی رطوبتی استفاده شد. پارامترهای مدل ونگنوختن با استفاده از نرم‎افزار رزتا نیز برآورد و سپس مقادیر به‎دست آمده از رزتا و روش فرکتالی با مقادیر پارامترهای ونگنوختن تعیین شده از نرم‎افزار RETC با هم مقایسه شدند. نتایج نشان داد که نرم‎افزار رزتا برآورد بهتری از پارامترهای مدل ونگنوختن نسبت به روش فرکتالی ارائه می‎دهد. در ‎نهایت، پارامترهای α و m تخمین زده‎شده مدل ونگنوختن که از روش‎های مختلف فوق‎الذکر به‎دست آمده بودند در ترکیب با رطوبت اشباع اندازه‎گیری‎شده برای تخمین رطوبت خاک در پتانسیل‎های ماتریک مختلف به‎کار گرفته شده و با مقادیر تعیین شده توسط RETC از طریق برازش مدل ونگنوختن بر داده‎های اندازه‎گیری‎شده، مقایسه شدند. نتایج حاصل حاکی از تخمین بهتر منحنی رطوبتی با استفاده از روش فرکتال نسبت به رزتا است. بنابراین با وجود برآورد بهتر پارامترهای مدل ونگنوختن به‎وسیله نرم‎افزار رزتا نسبت به روش فرکتالی، پیش‎بینی مقدار رطوبت خاک با استفاده از رزتا دقیق‎تر از روش فرکتالی نمی‎باشد. چون تخمین مقدار رطوبت نتیجه برهمکنش بین پارامترهای مدل ونگنوختن، m و α است.

کلیدواژه‌ها

موضوعات

عنوان مقاله [English]

Comparison of Fractal and Rosetta Approaches for Estimation of Soil Water Retention Curve

نویسندگان [English]

  • L Esmaeelnejad 1
  • J Seyedmohammadi 2
  • M Shabanpour 3
چکیده [English]

The van Genuchten (vG) function is often used to describe the soil water retention curve (SWRC) of unsaturated soils. The objective of this study was to evaluate a method to determine the vG model parameters m and α of 100 soil samples of Guilan province from the fractal dimension of SWRC. Also, we used two models introduced by Lenhard et al and vG for estimating m from pore size distribution index of Brooks and Corey (BC) model. In both of the mentioned methods, the relationship between pore size distribution index of BC and SWRC fractal dimension was used. Also, vG parameters using Rosetta software were estimated and then, the amounts of vG parameters from the Rosetta, fractal method and RETC were compared. Results showed that Rosetta software had a better estimation of vG parameters than the Rosetta. The estimated vG model parameters m and α obtained with the above-mentioned different methods, in conjunction with measured saturated water contents, were used to estimate water contents at different matric potentials and compared with determined values by RETC via fitting of vG model on the measured values. The estimated SWRC data via fractal method were compared with those obtained with the Rosetta model. Results showed that fractal method had more accurate performance for prediction of SWRC than the Rosetta. Even though, the Rosetta software could lead to better estimates of the vG model parameters than the fractal approach, it was not capable of predicting SWRC as accurately as the fractal approach. This is due to the fact that estimation of the water content is a result of an interaction between the estimated vG model parameters, α and m.

کلیدواژه‌ها [English]

  • Brooks and Corey
  • Lenhard
  • Tyler and Wheatcraft
  • van Genuchten parameters

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