بررسی تأثیر نصب موانع در بخش تعریض‌شده رودخانه بر نحوه انتقال بار بستر با استفاده از مدل آزمایشگاهی

نوع مقاله : مقاله پژوهشی

نویسندگان

1 دانش‌آموخته کارشناسی ارشد سازه‌های آبی گروه علوم و مهندسی آب دانشگاه بیرجند

2 دانشیار گروه علوم و مهندسی آب، دانشکده کشاورزی، دانشگاه بیرجند

3 استادیار گروه علوم و مهندسی آب، دانشکده کشاورزی، دانشگاه بیرجند

چکیده

نهشته‌شدن رسوب در سازه‌ها و مجاری انتقال آب، باعث ایجاد مشکلاتی نظیر کاهش ظرفیت و سرعت جریان و به­طور کلی کاهش راندمان سازه می‌شود. از جمله مسائلی که در رودخانه‌ها و طراحی سازه‌های آبیاری و آب‌رسانی نقش مهمی دارد، مسأله انتقال رسوب و کنترل آن است. در این پژوهش با استفاده از مدل آزمایشگاهی، تأثیر تعریض بستر به همراه نصب موانع در اندازه‌ها و شرایط مختلف در مسیر رودخانه‌هایی که دارای حمل رسوب زیادی به‌صورت بار بستر می‌باشند؛ بر نحوه انتقال رسوبات مورد بررسی قرار گرفت. ابتدا یک آزمایش شاهد در شرایط تعریض رودخانه بدون حضور مانع و سپس 21 آزمایش در شرایط تعریض با نصب موانع انجام شد.  نتایج نشان داد که نصب موانع بر حرکت بار بستر مؤثر است. با افزایش اندازه موانع، سرعت حرکت بار بستر و پیش‌روی رسوبات، کاهش و تله‌اندازی رسوبات افزایش یافت، به نحوی که با افزایش ابعاد موانع، کاهش پیش‌روی جبهه رسوبی در بخش تعریض شده نسبت به وضعیت شاهد (RS)، از حدود 15- درصد به حدود 41 درصد افزایش را نشان داد. هم‌چنین نتایج نشان داد با افزایش تعداد ردیف موانع، از سه به هفت ردیف، پیش‌روی رسوبات کاهش، تله‌اندازی رسوبات افزایش و کاهش پیش‌روی جبهه رسوبی در بخش تعریض شده نسبت به وضعیت شاهد (RS)، 24 درصد افزایش را نشان می‌دهد.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Investigating the Effect of Obstacle Installation in the Widened River Part on the Bed Load Transport Using a Laboratory Model

نویسندگان [English]

  • Hamid Ahani 1
  • Hossein Khozeymehnezhad 2
  • Mohammad hosein Najafi mood 3
1 M.Sc., Department of Water Science and Engineering, University of Birjand.
2 Associate Prof., Dept. of Water Science and Engineering, University of Birjand
3 Assistant Professor, Department. of Water Science and Engineering, University of Birjand.
چکیده [English]

Introduction
Sediment control is one of the issues of paramount importance in designing irrigation networks and water supply facilities. The most important methods of erosion and sedimentation management and control include basin management, sediment trap management in upstream, and sediment trap source management out of the river. Jafari et al. (2019) investigated the effect of submerged vanes and their dimensions on the bed load transport in the widened part of the river using a laboratory model. The results showed that by increasing the dimensions of submerged vanes, the speed of the bed load transport decreased, and as a result the performance of vanes improved. In a similar research strand, the present study evaluated the effect of obstacle installation and its size in the widened part of the river on the bed load transport using a laboratory model.
 
Methodology
Using a dimensional analysis of the effective variables in the widened part of the river and installing obstacles, this study identified the influential parameters on the bed load transport. Some experiments were then carried out by simulating the widened conditions of the river in a laboratory canal. Then, a witness experiment was carried out in the widened part of the river without the presence of an obstacle. This was followed by 21 experiments in the widened parts of the river by installing an obstacle. Linear obstacle arrangement in the basin was then performed in 5 rows and 3 columns and it was considered constant for all experiments. Moreover, the discharge rate and depth, according to the initial experiments and the amount and manner of sediment movement, were constant for all experiments and equal to 10 liters per second and 0.16 meters, respectively. In order to examine the effect of the obstacle size, 15 obstacles with 0.04 meter height (hb), different width (Wb) and length (Lb) with 0/02, 0/03, 0/04 and 0.05 meters were installed and tested. At the end of the performance, the main section (i.e., the widened part) of the bed load control was examined quantitatively and qualitatively. To examine the quantitative performance of the main section, equation (1) was used.
 




Rs =


(1)




 
In (1), Rs is the reduction in the distance of sediment flow in the widened part with an obstacle relative to the state without an obstacle (i.e., witness test), xe is the progression of sediment flow in the widened section without an obstacle, (xe- xb) is decreasing the progression of the sediment flow in the widened part with an obstacle relative to the widened conditions without an obstacle.  

کلیدواژه‌ها [English]

  • Sediment transport
  • sediment trapping
  • sedimentary front
  • river
  • obstacle specifications
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