کاربرد پره های مستغرق درکاهش آبشستگی موضعی تکیه گاه پل با دماغه گرد

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
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