بررسی آزمایشگاهی آستانه حرکت ذرات و تغییرات زمانی غلظت رسوب در فرسایش ناشی از جریان رواناب

نوع مقاله : مقاله پژوهشی

نویسندگان

1 دانش آموخته کارشناسی ارشد، مهندسی آب، دانشکده مهندسی عمران و محیط زیست، دانشگاه تربیت مدرس، تهران، ایران

2 گروه مهندسی آب، دانشکده مهندسی عمران و محیط زیست، دانشگاه تربیت مدرس، تهران، ایران

3 گروه علوم و مهندسی خاک، دانشکده مهندسی و فناوری کشاورزی، دانشگاه تهران، کرج، ایران

چکیده

فرسایش خاک تشدیدی به­عنوان مهم­ترین عامل تخریب منابع خاک و آب محسوب می‌شود. به‌طور معمول، فرآیند فرسایش خاک شامل جدا شدن و انتقال ذرات خاک توسط قطرات بارندگی، جریان کم­عمق سطحی و یا برهمکنش این دو عامل است. بر این اساس، آگاهی از آستانه حرکت ذرات رسوب و تغییرات غلظت رسوب نسبت به زمان در فرسایش ناشی از جریان می‌تواند باعث شناخت دقیق فرآیندهای حاکم بر فرسایش خاک و انتقال رسوب و برهمکنش احتمالی آن­ها و همچنین زمینه­ای برای افزایش دقت مدل‌های فرسایش خاک باشد. در تحقیق حاضر، آستانه حرکت ذرات و تغییرات زمانی غلظت رسوب در نمونه­ای ماسه­ای در شرایط آزمایشگاهی در سه شیب 1/3، 9/5، 9/8 درصد و با سه دبی در واحد عرض 78/4، 12/7 و 05/9 (×10-5 m2 s-1) در فلومی به ابعاد 40/2 متر طول و40/0 ‌متر عرض بررسی شد. نتایج نشان داد، منحنی شیلدز برای تعیین آستانه حرکت برای این تحقیق مناسب نبود. قدرت جریان آستانه حرکت ذرات، 035/0 وات بر مترمربع تعیین شد. همچنین با افزایش شیب و به تبع آن افزایش قدرت جریان تا 05/0 وات بر مترمربع، شدت فرسایش افزایش یافت و فرسایش خاک از حالت ورقه­ای به شیاری تبدیل شد. نتایج تحقیق نشان می­دهد که عامل اصلی تلفات خاک و تولید رسوب در دامنه­ها، تشکیل و توسعه فرسایش شیاری است. بنابراین یکی از راه­هایی که می­تواند به­طور موثر میزان فرسایش خاک را کنترل کند، جلوگیری از تشکیل شیار با روش­هایی همچون کشت نواری، تراس­بندی و بانکت­بندی است.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Laboratory Study of the Motion Threshold and Temporal Variation of Sediment Concentration in Flow-induced Erosion

نویسندگان [English]

  • Mohamadrza Vali 1
  • Farzin Nasiri Saleh 2
  • Hossein Asadi 3
1 Graduate Student,, Department of Water Engineering, Faculty of Civil & Environmental Engineering, Tarbiat Modares University, Tehran, Iran
2 Department of Water Engineering, Faculty of Civil & Environmental Engineering, Tarbiat Modares University, Tehran, Iran
3 Soil Science Department, Faculty of Agricultural Engineering and Technology, university of Tehran, Karaj, Iran
چکیده [English]

Accelerated soil erosion is the most important degradation factor of soil and water resources. Typically, soil erosion involves the detachment and transport of soil particles by rainfall, shallow surface flow or the interaction of these two factors. Therefore, understanding the motion threshold of sediment particles and temporal variation of sediment concentration in flow-induced can provide a detailed cognition of the processes inducing soil erosion and sediment transport and their eventual interactions. It is also important for increasing the accuracy of soil erosion models. In this study, the particle motion threshold and temporal variation of sediment were studied for a sandy sample at three slopes; 3.1, 5.9, 8.9% and-dunder three flow discharges of 4.78, 7.12 and 9.05 (×10-5 m2 s-1). This study was carried out in the laboratory conditions using a flume with 240 cm long by 40 cm width. The results showed that the Shields curve is not suitable for this study to determine the motion threshold. The threshold stream power of particle motion was determined 0.035 W m-2. Also, with increasing slope and consequently increasing stream power up to 0.05 W m-2, the erosion intensity increased and soil erosion changed from sheet erosion to rill erosion. The results indicate that the formation and development of rill erosion would be the main factor for soil loss and sediment production in hillslopes. Therefore, prevention of rill formation by strip croping, terracing and terrace farming is an effective strategy for soil conservation.

کلیدواژه‌ها [English]

  • Soil erosion
  • Steady flow
  • shear stress
  • Sediment size distribution
  • Shields parameter
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