بررسی آزمایشگاهی اثر پوشش سنگ ریزه سطحی بر ضریب زبری، تنش برشی و تلفات خاک

اسدزاده, فرخ; میرزایی, سلمان; گرجی, منوچهر; جعفری اردکانی, علی

بررسی آزمایشگاهی اثر پوشش سنگ ریزه سطحی بر ضریب زبری، تنش برشی و تلفات خاک

نوع مقاله : مقاله پژوهشی

نویسندگان

¹ استادیار گروه علوم خاک دانشگاه ارومیه

² دانشجوی دکتری علوم خاک دانشگاه شهرکرد

³ دانشیار گروه علوم خاک پردیس کشاورزی و منابع طبیعی دانشگاه تهران

⁴ عضو هیات علمی پژوهشکده حفاظت خاک و آبخیزداری

چکیده

شرایط سطح خاک مانند زبری، ساختمان، پوشش گیاهی و پوشش سنگریزه اهمیت زیادی در کنترل نفوذ آب به خاک، رواناب و فرسایش خاک دارد. پوشش سنگریزه سطحی به طور مستقیم فرآیندهای فرسایش را به خصوص در مناطق خشک و نیمه خشک که پوشش گیاهی کمی دارند، تحت تاثیر قرار میدهد. هدف از تحقیق حاضر، بررسی آزمایشگاهی اثر پوشش سنگریزه سطحی بر میزان تلفات خاک و خصوصیات هیدرولیکی جریان نظیر ضریب زبری و تنش برشی در یک نمونه خاک لسی از استان گلستان بود. در این تحقیق، شبیهسازی رواناب با استفاده از یک فلوم 5/0×6 متر و در شیب ثابت سه درصد انجام شد. تیمارها شامل سطوح مختلف پوشش سنگریزه (صفر، 10، 20 و 30 درصد) و دبی جریانهای سطحی (^4-10×5/0، ^4-10×1و ^4-10×5/1 مترمکعب در ثانیه) بودند. براساس نتایج، با افزایش پوشش سنگریزه از صفر به 30 درصد در دبیهای جریان ^4-10×5/0، ^4-10×1و ^4-10×5/1، به ترتیب سرعت نسبی جریان 9/68، 74/67 و 9/70 درصد کاهش یافت. مقادیر ضریب زبری و تنش برشی نسبی با افزایش پوشش سنگریزه به صورت خطی (99/0=R²) افزایش یافت. علاوه بر آن، با افزایش پوشش سنگریزه از صفر به 30 درصد، مقدار تلفات خاک نسبی در دبی جریانهای ^4-10×5/0، ^4-10×1و ^4-10×5/1 به ترتیب 0/85، 7/83 و 6/73 درصد کاهش یافت. کاهش تلفات خاک رابطه نمایی (98/0=R²) با پوشش سنگریزه را نشان داد.

کلیدواژه‌ها

عنوان مقاله [English]

Laboratory Investigation of Surface Rock Fragment Cover Effects on Roughness Coefficient, Shear Stress and Soil Loss

نویسندگان [English]

Farrokh Asadzadeh ¹
Salman Mirzaee ²
Manoochehr Gorji ³
Ali Jafari-Ardakani ⁴

¹ Assistant Professor, Department of Soil Science, Urmia University, Iran

² PhD Student, Department of Soil Science, Shahrekord University, Shahrekord, Iran

³ Associate Professor, Department of Soil Science, University of Tehran

⁴ Soil Conservation and Watershed Management Research Institute, Tehran, Iran

چکیده [English]

Soil surface conditions such as roughness, structure, vegetation and rock fragment cover have very important effects on inﬁltration, run-off and soil erosion. Rock fragments at the soil surface directly affects soil erosion processes, particularly in arid and semiarid environments where vegetation cover is poor. The objective of the present research was to study the influence of rock fragment cover on the rate of soil loss and the hydraulic properties of flow such as roughness coefficient and shear stress in a loess soil sample from Golestan province. The investigation was conducted using a flume with 6 m length, 0.5 m width, and 3% gradient. The treatments included rock fragment covers (0, 10, 20 and 30%), and flow discharges of 0.5, 1.0 and 1.5 (10^{-4 m3} s^-1). With increasing of rock fragment cover from 0 to 30% in flow discharges of 0.5, 1.0 and 1.5 (10^{-4 m3} s^-1), relative velocity of water flow decreased 68.9, 67.7 and 70.9%, respectively. The value of relative roughness coefficient and shear stress increased linearly (R²=0.99) with increasing of rock fragment covers. In addition, with increasing of rock fragment cover from 0 to 30%, the rate of relative soil loss in flow discharges of 0.5, 1.0 and 1.5 (10^{-4 m3} s^-1) decreased 85.0, 83.7 and 73.6%, respectively. Decreasing soil loss rate was related to Rock fragment cover by an exponential function (R²=0.98).

کلیدواژه‌ها [English]

Rock fragment cover
Roughness coefficient
Shear stress
Soil loss

مراجع

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