بررسی آزمایشگاهی تاثیر برداشت مصالح در آبشستگی اطراف گروه پایه‌های مسلح شده

نوع مقاله : مقاله پژوهشی

نویسندگان

1 استادیار، گروه مهندسی عمران، دانشکده فنی و مهندسی، دانشگاه مراغه، مراغه، ایران

2 دانشیار، گروه مهندسی عمران، دانشکده فنی و مهندسی، دانشگاه مراغه، مراغه، ایران

3 دانشجوی کارشناسی ارشد سازه‌های هیدرولیکی، گروه مهندسی عمران، دانشکده فنی و مهندسی، دانشگاه مراغه، ایران

چکیده

پدیده آبشستگی اطراف پایه‌های پل به خصوصیات هیدرولیکی جریان، شکل و فاصله قرارگیری پایه‌ها نسبت به هم، جنس و اندازه دانه‌بندی بستر رودخانه‌‌ها بستگی دارد. هدف از تحقیق حاضر بررسی تاثیر گودال حاصل از برداشت مصالح در میزان آبشستگی اطراف گروه‌پایه‌ها است. بنابراین برای کاهش اثر منفی این برداشت، از گروه‌پایه‌هایی با دورپیچ کابل به‌ عنوان مسلح‌کننده استفاده گردید. گروه­پایه­ها از سه پایه متوالی در راستای جریان تشکیل شده­اند. آزمایش­ها در دو حالت ساده و مسلح­شده ( v شکل)، در بستر ماسه­ای با دانه­بندی 78/0 میلی­متر به طول 25/4 متر، درون کانالی به طول 13 متر و عرض 2/1 متر انجام گرفته است. تاثیر برداشت مصالح بر میزان آبشستگی در هر دو قسمت بالادست و پایین‌دست گروه‌پایه‌های مذکور در شرایط جریان زیر بحرانی (محدوده عدد فرود 25/0 و 5/0) مورد بررسی قرار گرفت. نتایج نشان داد که در تمام آزمایش‌ها، برداشت مصالح از بالادست گروه‌پایه‌ باعث کاهش و برداشت از پایین‌دست گروه‌پایه، موجب افزایش عمق آبشستگی بیشینه گردید. همچنین با افزایش عدد فرود از 25/0 به 5/0، در تمام پایه‌ها و برای هر دو بستر بدون گودال (الف) و با گودال (ب)، عمق آبشستگی افزایش چشم‌گیری داشته است. بطوریکه کمترین افزایش آبشستگی برای حالت (الف) و (ب) به ترتیب حدودا برابر 44 و 66 درصد، مربوط به پایه‌ آخر از گروه‌پایه پایین‌دست و بیشترین افزایش آبشستگی به ترتیب 75 و 76 درصد در پایه اول از گروه‌پایه بالادست مشاهده گردید.

کلیدواژه‌ها

موضوعات

عنوان مقاله [English]

Experimental Investigation of the River Materials Mining Effect on the Scouring Around Armed Pier Groups

نویسندگان [English]

  • Mahdi Majedi Asl 1
  • Rasoul Daneshfaraz 2
  • saeideh valizadeh 3
1 Assistant Professor, Department of Civil Engineering, Faculty of Engineering, University of Maragheh, Maragheh, Iran.
2 Associate Professor, Department of Civil Engineering, Faculty of Engineering, University of Maragheh, Maragheh, Iran.
3 M.Sc. Student, Department of Civil Engineering, Faculty of Engineering, University of Maragheh, Maragheh, Iran.
چکیده [English]

The scouring phenomenon around the bridge piers depends on the hydraulic properties of the flow, shape, and spacing of the pier relative to each other, the material and grading of the rivers bed. The purpose of this study was to investigate the effect of cavity, caused by materials mining, on scouring around the pier groups. Therefore, in order to reduce the negative effect of this mining, pier groups armed with cable were used. Pier groups were performed of three consecutive piers in the direction of flow. The experiments were carried out in two simple and armed modes (v shape), in sand bed with a median grain size of 0.78 mm, with a length of 4.25 meters, in a canal with 13 meters in length and 1.2 meters in width. The effect of materials mining on scouring in upstream and downstream of the mentioned pier groups was investigated under subcritical flow conditions (range 0.25-0.5). The results showed that in all experiments, materials mining from the upstream of the pier group reduced the scour maximum depth, but mining from the downstream of the pier group increased the scour maximum depth. Also, with increasing the Fraud number from 0.25 to 0.5, the scour depth was significantly increased in all piers and for two beds; without a pithole bed (a) and with a pithole bed (b). So that the least increase in scouring for A and B conditions was about 44 and 66%, respectively for the last pier in downstream pier group and the most increase in scoring was observed to be 75 and 76%, respectively for the first pier in upstream pier group.

کلیدواژه‌ها [English]

  • pier group
  • armed
  • pithole
  • scour

مراجع

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تحقیقات آب و خاک ایران
دوره 50، شماره 6
آبان 1398
صفحه 1363-1380

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