نوع مقاله : مقاله پژوهشی
نویسندگان
1 دانشجوی دکتری سازه‌های آبی، دانشکده کشاورزی، دانشگاه شهید باهنر کرمان
2 دانشیار، دانشکده کشاورزی، دانشگاه شهید باهنر کرمان
چکیده
تغییرات ژئومورفولوژیک بستر و کناره رودخانه‌ها می‌تواند سرعت مهاجرت و توسعه پیچان‌رودها را تحت تاثیر قرار دهد. تغییر ناگهانی شیب بستر رودخانه یکی از رایج‌ترین تغییرات ژئومورفولوژیک در مسیر رودخانه است. اندازه‌گیری سرعت مهاجرت و توسعه پیچان‌رودها و اتخاذ تدابیر لازم برای حفاظت سازه‌های قرار گرفته در کنار و روی رودخانه از جمله اقدامات مهندسی در عرصه مهندسی رودخانه می‌باشد. بدین‌منظور، برای مطالعه و اندازه‌گیری سرعت مهاجرت و توسعه پیچان‌رودها با رخداد تغییر ناگهانی شیب مسیر جریان، آزمایش‌هایی در فلوم آزمایشگاهی با بستر فرسایش‌پذیر انجام گرفت. کانال جریان بر روی بستر رسوبی حفر شد و برای سه عرض مختلف کانال (طول موج‌های مختلف خم ابتدایی)، سه دبی و سه شیب متفاوت بستر در دو گروه آزمایش با حضور و عدم حضور رخداد تغییر ناگهانی شیب (آزمایش‌های شاهد) سرعت مهاجرت و توسعه پیچان‌رودها مورد مطالعه قرار گرفت. نتایج نشان داد که جریان در جهت تعدیل تغییر ناگهانی شیب در پایین‌دست، با سرعت بسیار بالایی شروع به ایجاد خم‌های پیچان‌رودی کرده، در نتیجه آن سرعت مهاجرت طولی پیچان‌رودها نسبت به آزمایش‌های شاهد افزایش و سرعت توسعه عرضی کاهش نشان داده است. افزایش سرعت مهاجرت طولی پیچان‌رودها تا 32 درصد و کاهش سرعت توسعه عرضی تا 36 درصد از مقایسه نتایج حاصل از آزمایش‌ها در حضور رخداد تغییر ناگهانی شیب و عدم حضور آن به‌دست آمده است.
کلیدواژه‌ها
عنوان مقاله [English]
Laboratory investigation of migration and expansion rate related to meandering rivers with knickpoint at downstream
نویسندگان [English]
- Samira Rezapourian Qahfarokhi 1
- Mohammad Mehdi Ahmadi 2
- Kourosh Qaderi 2
1 PhD Student, Faculty of Agriculture, Shahid Bahonar University of Kerman, Kerman, Iran
2 Associate Professor, , Faculty of Agriculture, Shahid Bahonar University of Kerman, Kerman, IranKerman, Iran
چکیده [English]
The geomorphological changes of the bed and bank of rivers can affect the migration and expansion rate of the meandering rivers. A knickpoint in the bed slope is one of the most common geomorphologic changes in the river. Measuring the migration and expansion rate of meandering rivers, in addition to taking the necessary actions in order to protect the structures located along and over the river are considered as engineering measures in the field of river engineering. In this regard, to study and measure the rate of migration and expansion of meandering rivers with knickpoint in the flow at downstream, experiments were carried out in a laboratory flume with an erodible bed. The channel was carved on the sedimentary bed, and was studied and evaluated the migration and the expansion rate in to two experimental groups in the presence and absence of the knickpoint (control tests) for three different widths of the channel (different wavelengths of the initial bend), three discharges, and three different bed slopes. Results showed that the flow began to create meandering bends at a very high rate in order to modify the knickpoint at downstream, and as a result, the migration rate of meander has increased compared to the control experiments and decreased the expansion rate. An increase in the rate of migration up to 32% and the decrease in the rate of expansion up to 36% are achieved by comparing the results of experiments with presence of the knickpoint at downstream and its absence.
کلیدواژه‌ها [English]
- Alluvial rivers
- Floodplain
- Flume
- Planform
- River engineering
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