بررسی اثر استفاده از پوشش غیر فرساینده بر میزان بادبردگی ذرات ماسۀ تل حمید به کمک تست تونل باد

پدیدۀ فرسایش بادی و حرکت ماسه‌های روان از چالش‌های جدی سرزمین‌های خشک محسوب می‌شود. در پژوهش حاضر برای کنترل طوفان‌های ماسه و تثبیت گردوغبار، پوشش سنگ‌ریزه پیشنهاد شده است. برای این کار با انتقال ماسه از منطقۀ بیابانی بلاک ریلی منتظر قائم تل حمید تاثیر پوشش سنگ‌ریزه با تراکم 30، 50 و 75% در میزان باد بردگی ذرات شن و ماسه به کمک تست تجربی تونل باد و در سرعت‌های متفاوت مورد بررسی قرار گرفت. نتایج نشان داد که برای سرعت‌های باد تا 10 متر بر ثانیه نیازی به پوشش‌دهی سنگ‌ریزه نیست ولی در سرعت‌های بیشتر از 20 متر بر ثانیه با افزایش درصد پوشش سنگ‌ریزه میزان فرسایش بادی به‌صورت توانی کاهش می‌یابد در سرعت‌های باد حدود 16 متر بر ثانیه کارایی پوشش 50 و 75% به هم نزدیک بوده و تقریباً نتیجۀ یکسانی در بر داشت. ازاین‌رو در این ‌گونه مناطق پوشش بیشتر از 50%، فقط هزینۀ کار را بیشتر کرده ولی در نتیجه کار تاثیر قابل ‌توجهی نخواهد داشت؛ بنابراین در مناطقی که امکان استفاده از سایر روش‌ها به دلایل مختلف ادافیکی یا اقلیمی وجود نداشته باشد می‌توان از پوشش‌دهی مواد غیر فرساینده مانند ریگ یا پوشش‌های سنگ‌ریزه‌ای به‌عنوان یک راهکار عملی برای جلوگیری از فرسایش بادی و گردوغبار استفاده کرد.

Wind Tunnel Experimental Investigation of the Effect of Using Non-Erodible Coatings on Sand Transport Rate of Talle-Hamid Desert Area

Introduction: Due to the detrimental consequences of the application of stabilizers such as mulch and other protectives on the soil surface, including the wafting of bad smell, blackening of the ground, increasing thermal coefficient, warming of the whole area, and even destruction of plants and their unsustainability in nature, wide use of such stabilizers could not be considered as a useful solution to control wind erosion. Therefore, to solve the problem of sandstorms in Iran and get the desertschr('39') soil stabilized, this study proposes that deserts be coated with nonerodible materials (e.g., gravel, sandblasting, etc.) Materials Methods: Based on the purpose of this study, the effect of gravel cover with 30%, 50%, and 75% coverage on the sandblasting rate of MontazerQaem TaleHamid desert was investigated using the wind tunnel. To investigate the effect of different gravel coatings on the sand particle transport rate, first, a sand sample was gathered from the TalleHamid area in Tabas, located 209 km off the Bafgh Railway, at 55/89 latitude and 32/93 longitude degrees, respectively, and the particle density of sand particles size was measured using standard ASTM D85402. Its amount was found to be 2724 kg/m3. In the next stages, dry aggregation of sand particle size was first extracted from different parts of the MontazerQaemTalleHamid track. According to the ASHTO T27 standard, at least 500 gr random fine sample particles should be collected from each site to sieve. Four samples were collected from sites that were 209, 213, 217, 222, and 222.7 km off Tabas. Having enumerated Standardsized sieved particles, we used a vibrating machine to shake different particle diameters for at least 15 minutes. Furthermore, scales with a minimum accuracy of 0.01gr were used to weigh particles of different diameters. According to the standard of reconstitution for fine particles such as sand, the minimum sample size for sieving is 300gr, and the sample should be dried at 110 ° C in a threestage oven. Then, these particleschr('39') transportation rate was measured at different wind speeds for uncovered gravel samples. Results Discussion: Initially, by increasing the wind speed from 1 m/s to 8 m/s, it was found that the particlechr('39')s creeping movement started at 6.9 m/s and its creeping speed was 6.9 m/s. The index sample was then placed in the wind tunnel for 5 minutes at different speeds of 9.9, 12.4, 17.2, and 22 m/s, and sand particle transportation was determined. It was also found that wind erosion increased by increasing wind speed polynomials. Subsequently, sands with 3050% and 75% gravel cover were inserted into the wind tunnel for 5 minutes at wind speeds of 10.5, 15.7, and 22.9 m/s. Having determined the rate of wind erosion, we observed that the wind erosion rate decreased with an increasing percentage of gravel cover at a certain speed. We also found that the greatest effect on decreasing wind erosion rate occurred at wind speed 22.9 m/s, with the reduction percentage of erosion being 67.5%. The study results showed that the wind erosion rate decreased with an increasing rate of gravel cover at a certain speed, and the highest effect of graved on reducing wind erosion was reported for gravel cover of 75%. Therefore, covering the surface of a sandy desert with noncorrosive materials such as sand or gravel could be a practical solution for preventing wind erosion. Conclusion: The effects of nonerodible coating or gravel on the rate of sand particle erosion were investigated via the wind tunnel, the results of which showed that the samples with gravel cover were effective in reducing wind erosion of sand particles. The greatest reduction in wind erosion rate was reported for the sites covered by 75% gravel. According to research conducted in the Chinese deserts, gravel cover with eroding sand particles and reducing wind velocity at the sand surface could well improve erosive sand levels. The present study also showed that at 22.9 m/s wind speed and 75% gravel cover, the erosion rate decreased by 67.5%. Therefore, to reduce the effects of sandstorms in Iran and stabilize the sandy desert area, nonerodible coating such as gravel would be recommended instead of mulch.