نوع مقاله : مقاله پژوهشی
نویسندگان
1 دانشگاه صنعتی شاهرود
2 دانشگاه آزاد واحد دزفول
چکیده
ادارۀ فدرال بزرگراههای آمریکا در بررسی آمار شکست پلها به این نتیجه رسیده است که دلیل اصلی شکست آنها آبشستگی موضعی اطراف تکیهگاههای جانبی، در مقایسه با آبشستگی پایههای پل، است.. روشهایی مختلف برای کاهش آبشستگی موضعیدر اطراف پایههاوتکیهگاههایجانبیپلپیشنهاد شده که یکی از آنها استفاده از پرههای مستغرق است. در پژوهش حاضر به بررسی عملکرد استقرار پرههای مستغرق در کاهش آبشستگی موضعی تکیهگاه پل با دماغۀ گرد بهصورت آزمایشگاهی پرداخته شده است. آزمایشها در یک فلوم با مقطع مرکب و با استفاده از رسوبات غیرچسبنده با قطر متوسط 1 میلیمتر و در دو مرحله اجرا شدند: بدون حضور پرههای مستغرق و با حضور پرههای مستغرق. پرهها با طول 10 و ارتفاع 33/3 سانتیمتر (3L/H=)، در پنج نوع آرایش دو ردیفه و با زاویۀ 20 درجه نسبت به جریان در جلو تکیهگاه پل مستقر شدند. نتایج این پژوهش نشان میدهد که عملکرد پرههای مستغرق در کاهش آبشستگی اطراف تکیهگاه قابل توجه و موجب حرکت حفرۀ آبشستگی و دور کردن آن از دماغۀ تکیهگاه به سمت مرکز کانال شده است. همچنین، استفاده از پرههای مستغرق با پنج نوع آرایش مختلف نشان میدهد که بهطور متوسط این سازه میتواند 1/60 درصد عمق آبشستگی را در اطراف تکیهگاه پل کاهش دهد. نتایج بهدست آمده همچنین نشان میدهد که بهترین عملکرد را آرایش دو ردیفه موازی دارد که در آن پرههای ردیف اول با فاصلۀ 5 سانتیمتر و ردیف دوم با فاصلۀ 15 سانتیمتر از تکیهگاه قرار میگیرند و موجب کاهش 74/71 درصد از حداکثر عمق آبشستگی شدهاند.
کلیدواژه‌ها
عنوان مقاله [English]
Application of the Submerged Vanes on Reduction of Local Scour around the Bridge Abutment with Rounded Nose
نویسنده [English]
- Ebrahim Nohani 2
2 Deptartment of Hydraulic Structures, Dezful Branch, Islamic Azad University, Dezful, Iran
چکیده [English]
The statistics of bridge failures by US Federal Highway Administration show that the local scour around the bridge abutment is main reason compared to the local scour of piers. Various methods have been suggested for the control and reduction of local scour around the bridge piers and abutment. Using submerged vanes is one of these methods. In this study, the effect of submerged vanes to reduce the local scour around the bridge abutments with rounded nose was studied. Experiments conducted in a compound channel with non-cohesive sediments with diameter (d50) of 1 mm. Experiments carried out in two stages: in first stage without using submerged vanes and at the second stage with the presence of submerged vanes. Two rows of submerged vanes with length of 10 cm, height of 3.33 cm (L/H =3) and with angle of 20° was used. The results showed that the geometric properties of the scour hole in the nose of abutment was similar to the results obtained by other researchers. Results also showed that at all flow conditions submerged vanes reduced the scour hole around the bridge abutment and they moved the scour hole from the near of the abutment to the center of channel. Also the results showed that using submerged vanes averagely reduced 60.1% of the maximum scour depth. Finally the best layout of submerge vanes which had a distance of 5 and 15 cm between first and second rows with abutment, reduced the maximum scour depth by 71.74 percent.
Keywords: Abutment, Compound Channel, Local Scour, Submerged Vanes
کلیدواژه‌ها [English]
- Abutment
- Compound channel
- Local Scour
- Submerged Vanes
Akan, A. O. 2011. Open Channel Hydraulics. Butterworth-Heinemann. Oxford.
Alemi, Z., Ghomeshi, M. and Mohammadi, S. 2012. The application of collar on the scour reduction at bridge rectangular abutment in composit channel. J. Irrig. Water Eng. 3(10): 29-41. (in Persian)
Breusers, H. N. C., Nicollet, G. and Shen, H. W. 1977. Local scour around cylindrical piers. J. Hydraul. Res. 153, 211-252.
Brice, J. C. and Blodgett, J. C. 1978. Countermeasures for Hydraulic Problems at Bridges: Analysis and assessment (Vol. 1). Office of Research and Development. Federal Highway Administration.
Chang, F. F. 1973. A statistical summary of the cause and cost of bridge failures. Final Report. No. FHWA-RD-75-87
Chiew, Y. M. 2004. Local scour and riprap stability at bridge piers in a degrading channel. J. Hydraul. Eng. 130(3): 218-226.
Dehghani, A. A., Azamathulla, H. M., Hashemi-Najafi, S. A. and Ayyoubzadeh, S. A. 2013. Local scouring around L-head groynes. J. Hydrol. 504, 125-131.
Davis, S. R. 1984. Case histories of scour problems at bridges. Transportation Research Record.
Emamgholizadeh, S. 2015. Open Channel Hydraulics. Shahrood University of Technology Press. (in Persian)
Ghorbani, B. and Kells, J. A. 2008. Effect of submerged vanes on the scour occurring at a cylindrical pier. J. Hydraul. Res. 46(1): 610-619.
Heidarpour, M., Afzalimehr, H. and Izadinia, E. 2010. Reduction of local scour around bridge pier groups using collars. Int. J. Sediment. Res. 25: 411-422.
Hey, R. D. 1995. Environmentally Sensitive River Engineering. In: Calow, P. and Petts, G. E. (Eds.) The Rivers Handbook: Vol. 2. Blackwell Scientific Pub. Oxford. U. K.
Hosseini, H., Husseinzadeh-Dalir, A., Farsadizadeh, D., Arvanaghi, H. and Ghorbani, M. A. 2011. Simultaneous effects of submerged vanes and collar on scour reduction around rectangular piers with rounded nose. Water Soil Sci. 22(3): 87-101. (in Persian)
Kummar, V., Ranga Raju, K. G. and Vittal, N. 1999. Reduction of local scour around bridge piers using slot and collar. J. Hydraul. Eng. 125(12): 1302-1305.
Khademi, K., Shafaie, M. and Khozeimehnejad, H. 2014. Experimental investigation of flow and scour around bridge abutments with attached submerged vane. J. Irrig. Water Eng. 5 (17): 56-66. (in Persian)
Lauchlan, C. S. 1999. Pier scour countermeasures. Ph. D. Thesis. University of Auckland. Auckland.
New Zealand.
Melville, B. W. and Chiew, Y. M. 1999. Time scale for local scour at bridge piers. J. Hydraul. Eng. 125(1): 59-65.
Melville, B. W. and Coleman, S. E. 2000. Bridge Scour. Water Resources Pub. LLC. Clorado. U. S. A.
Mia, M. F. and Nago, H. 2003. Design method of time-dependent local scour at circular bridge pier. J. Hydraul. Eng. 129(6): 420-427.
Johnson, P. A., Hey, R. D., Tessier, M. and Rosgen, D. L. 2001. Use of vane for control of scour at vertical wall abutments. J. Hydraul. Eng. 127(9): 772-778.
Odgaard, A. J. and Kennedy, J. F. 1983. River-bend bank protection by submerged vanes. J. Hydraul. Eng. 109(8): 1161-1173.
Odgaard, A. J. and Wang, Y. 1991. Sediment management with submerged vanes. I: Theory. J. Hydraul. Eng. 117(3): 267-283.
Raudkivi , A. J. 1998. Loose Boundary Hydraulics. CRC Press.
Raudkivi, A. J. and Ettema, R. 1983. Clear-water scour at cylindrical Piers. J. Hydraul. Eng. 1093,
338-350.
Richardson, E. V. and Davis, S. R. 2001. Evaluating Scour at Bridges. 4th Ed. Hydraulic Engineering Circular No. 18. Federal Highway Administration. Washington, D. C. USA.
Rosgen, D. L. 1996. Applied river Morphology. Wildland Hydrology. Pagosa Spring, Co.
Samimiy-Behbahan, T., Barani, G. H., Khanli, M. and Khanjani, M. 2006. Experimental investigation of submerged vanes effect on scouring of bridge piers. National Congress of Irrigation and Drainage Networks Management. Faculty of Water Sciences Engineering. Shahid Chamran University. Ahvaz, Iran. (in Persian)
Shojaei, P., Farsadizadeh, D. and Hosseinzadeh-Dalir, A. 2011. Effects of combined submerged vanes and collar in reducing scour of base cylindrical bridges. J. Sci. Tech. Agric. Nat. Resour. (Soil Water Sci.) 15(57): 33-23. (in Persian)
Shafaie-Bejestan, M. 2008. Hydraulic Transport. Shahid Chamran University Press. (in Persian)
Shariati, H. and Khodashenas, S. R. 2015. Investigation of control methods on local scouring around the bridge piers. J. Water Sustain. Dev. 1(3): 43-52. (in Persian)
Zarrati, A. R., Chamani, M. R. Shafaie-Bejestan, M. and Latifi, M. 2010. Scour countermeasures for cylindrical piers using riprap and combination of collar & riprap. Int. J. Sediment Res. 25, 313-322.
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