مطالعه آزمایشگاهی تغییرات الگوی جریان و توپوگرافی بستر در اثر تغییر زاویه آبشکن باز توری سنگی در کانال با بستر فرسایش پذیر

نوع مقاله: مقاله پژوهشی

نویسندگان

1 دانش آموخته کارشناسی ارشد مهندسی آب و سازه های هیدرولیکی دانشگاه بوعلی سینا

2 استادیار گروه مهندسی عمران دانشگاه بو‌علی‌سینا.

3 دانش آموخته کارشناسی ارشد مهندسی آب و سازه‌های هیدرولیکی دانشگاه بو‌علی‌سینا.

چکیده

از ﺟﻤﻠﻪ روش­های ﺣﻔﺎﻇﺖ ﺳﻮاﺣﻞ رودخانه، ﺳﺎﺧﺖ اﻧﻮاع آبشکن­هاﺳـﺖ. سازه­های آبشکن، هر چند با اهداف رسوب­گذاری و جلوگیری از فرسایش کناره­ها و حواشی رودخانه و تثبیت موقعیت آن احداث می­شوند، در عین حال، خود تحت تأثیر پدیده فرسایش  ناشی از تمرکز جریان می­باشند. در این تحقیق تاثیر زاویه اتصال به ساحل آبشکن باز توری­سنگی با تخلخل 30 و 50 درصد بر الگوی جریان و توپوگرافی بستر مورد بررسی قرار گرفت. نتایج نشان می­دهد آبشکن­های قائم تأثیر مخرب­تری بر توپوگرافی بستر داشته و بعد از آن آبشکن دافع با تغییرات عمده در الگوی جریان اثرهای قابل­ توجهی بر ابعاد حفره آبشستگی دارد. در آبشکن قائم، بیشترین تغییرات مربوط به افزایش سرعت طولی جریان در دماغه­ی آبشکن و به دلیل تنگ­شدگی بیشتر مجرا و طول مؤثر بیشتر آبشکن می­باشد. آبشکن­های دافع با دفع جریان به سمت دیواره مقابل و اغتشاش زیاد به­دلیل مخالفت با جهت اصلی جریان پس از آبشکن قائم تغییرات زیادی در توپوگرافی بستر ایجاد کرده و نسبت به آبشکن جاذب حفره آبشستگی بزرگ­تری ایجاد می­کند.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

The Experimental Study of the Flow Pattern and Bed Topography Changes due to Variations in the Angle of the Gabion Spur Dike in the Open Channel with Erodible Bed

نویسندگان [English]

  • Zainab Badpa 1
  • Majid Fazli 2
  • Sedighe Pazin 3
1 MSc of Water Engineering and Hydraulic Structures, Faculty of Engineering, Bu-Ali Sina University.
2 Assistant Professor of civil Engineering, Faculty of Engineering, Bu-Ali Sina University.
3 MSc of Water Engineering and Hydraulic Structures, Faculty of Engineering, Bu-Ali Sina University.
چکیده [English]

The construction of structures such as spur dikes in open channels and rivers is done to control the coastal erosion or water guidance and diversion. Scouring due to changes in the pattern of flow around the structure may result in instability and structural insufficiency, and if designed improperly, it may lead to complete degradation. Thus, the flow pattern and scour depth around the spur dike should be carefully considered. In effect, the type of spur dike used in each project, depending on its usage in the flow path, the depth of scouring and economic considerations must be carefully selected. The open gabion spur dike is one of the most affordable ones and is of high quality in terms of efficiency and ease of construction.
 A lot of research has been already conducted on impervious and angled spur dikes, including that of Ezzeldin et al.. In their research, they performed experiments on a blade spur dike at various angles ( 30,60 and 90 degree)  and reported that the spur dike at 30 degrees was best  in terms of depth of scouring and coastal protection. The maximum scour areas for the spur dike in their research were 90 and 60 degrees upstream of the spur dike, while the maximum scour area for the spur dike is 30 degrees along the length of the spur dike. Moreover, scour at 90 ° and 60 ° was equal, and in some cases higher scouring at a 60 ° angle and an increasing cost of constructing the spur dike in angular mode (Because of the real length of more in equal terms). The use of this type of spur dike was unrealistic at an angle of 60 degrees. In addition, Nagy (2005) showed a time test for the vertical and attracting spur dikes, as the scour rate for larger Froude number was higher, and the scour rate for the vertical state was greater than the attracting state. He further concluded that the angled spur dike had less scour depth and volume. Conducting experiments on the scouring around a trapezoidal spur dike at three angles to the downstream of the adjoining coast in two constricted ratios of 0.25 and 1.05, Kuhnle (2002) concluded that the 45 degree spur dike created the most scouring in the area adjacent to the coast, while less scouring was observed for the spur dikes of 90 and 135 degrees .

کلیدواژه‌ها [English]

  • gabion spur dike
  • flow pattern
  • Bed topography
  • angle of spur dike
1-    Chang, F. and Davis, S., 1998. Maryland SHA Procedure for Estimating Scour at Bridge Abutments Part 2-Clear Water Scour. In Stream Stability and Scour at Highway Bridges: Compendium of Stream Stability and Scour Papers Presented at Conferences Sponsored by the Water Resources Engineering (Hydraulics) Division of the American Society of Civil Engineers (pp. 398-398). ASCE.

 

2-    Duan, J.G., 2009. Mean flow and turbulence around a laboratory spur dike. Journal of Hydraulic Engineering, 135(10), pp.803-811.

 

3-   Ezzeldin, M.M., Saafan, T.A., Rageh, O. and Nejm, L., 2007. Local scour around spur dikes. In Eleventh International Water Technology Conference, IWTC11. Sharm El-Sheikh (pp. 779-795).

 

4-    Fei-Yong, C. and Ikeda, S., 1997. Horizontal separation flows in shallow open channels with spur dikes. Journal of Hydroscience and hydraulic Engineering, 15(2), pp.15-30.

 

5-    Kermannejad, J. Dehghani, A. Fathi moghadam, M. Mahmodian, M., 2011. Investigation of Effect Porosity on Scour Depth Around L-head Groins with Clapper toward Downstream and Upstream under Clear Water Condition. Journal of  Water and Soil, Vol. 25. Nom 2: 305-314. (In Persian)

 

6-    Kuhnle, R.A., Alonso, C.V. and Shields, F.D., 1999. Geometry of scour holes associated with 90 spur dikes. Journal of Hydraulic Engineering, 125(9), pp.972-978.

 

7-    Kuhnle, R.A., Alonso, C.V. and Shields Jr, F.D., 2002. Local scour associated with angled spur dikes. Journal of Hydraulic Engineering, 128(12), pp.1087-1093.

 

8-    McCoy, A., Constantinescu, G. and Weber, L., 2006. Exchange processes in a channel with two vertical emerged obstructions. Flow, turbulence and combustion, 77(1-4), pp.97-126.

 

9-    Mioduszewski, T., Maeno, S. and Uema, Y., 2003, November. Influence of the spur dike permeability on flow and scouring during a surge pass. In International Conference on Estuaries and Coasts (pp. 380-388).

 

10- Nagy, H.M., 2005. Hydraulic evaluation of emerged and submerged spur-dikes: temporal bed evolution and equilibrium state characteristics. Journal of  Alexandria Engineering, 44(2), pp.279-290.

 

11- Peng, J., Kawahara, Y. and Tamai, N., 1996. Numerical analysis of three-dimensional turbulent flows around submerged groins. In Managing Water: Coping with Scarcity and Abundance (pp. 244-249). ASCE.

 

12- Rajaratnam, N. and Nwachukwu, B.A., 1983. Flow near groin-like structures. Journal of Hydraulic Engineering, 109(3), pp.463-480.

 

13- Tominaga, A., Ijima, K. and Nakano, Y., 2001. Flow structures around submerged spur dikes with verious relative height. In PROCEEDINGS OF THE CONGRESS-INTERNATIONAL ASSOCIATION FOR HYDRAULIC RESEARCH (pp. 421-427).

 

14- Uijttewaal, W.S., 2005. Effects of groyne layout on the flow in groyne fields: Laboratory experiments. Journal of Hydraulic Engineering, 131(9), pp.782-791.

 

15- Yang, C.T., 1996. Sediment transport: theory and practice. MCGRAW-HILL BOOK CO,(USA). 1996