اثر خاک‌پوش‌های لیگنوسلولزی بر مقامت برشی ماسه بادی

فرسایش بادی یکی از جنبه‌های مهم تخریب اراضی به‌ویژه در مناطق خشک و نیمه‌خشک جهان محسوب می‌شود. استفاده از انواع خاک‌پوش‌های سازگار با محیط‌زیست، یکی از روش‌هایی است که به‌منظور کاهش فرسایش بادی و تثبیت ماسه‌های روان به کار می‌رود. هدف از این تحقیق، بررسی امکان استفاده از لیگنوسلولز باگاس به‌عنوان یک خاک‌پوش آلی برای تثبیت ماسه‌های روان است. این تحقیق به‌صورت آزمایشگاهی و در قالب طرح کاملاً تصادفی و با سه تکرار انجام شد. تیمارهای مورد استفاده عبارت بودند از: نانولیگنوسلولز، میکرولیگنوسلولز و تیمار شاهد. به‌منظور ارزیابی کارایی این مواد، مقاومت برشی در حالت اشباع و خشک اندازه‌گیری شد و داده‌ها با استفاده از نرم‌افزار spss مورد تجزیه و تحلیل آماری قرار گرفتند. با توجه به نتایج به‌دست‌آمده در حالت اشباع تیمار میکرولیگنوسلولز (gr/0.3m2 10) با ضخامت دولایه با مقاومت برشی kn/m2 13.6 و در حالت خشک تیمار ترکیب نانولیگنوسلولز و لیکورسیاه (gr/0.3m2 10) با ضخامت دولایه با مقاومت برشی kn/m2 39 به‌ترتیب در طبقۀ خوب و بسیار خوب قرار گرفته‌اند. بنابراین، می‌توان توصیه کرد که بهتر است این نوع خاک‌پوش‌ها در عرصۀ طبیعی مورد آزمایش قرار گیرند و در صورتی ‌که از عملکرد مناسبی برخوردار باشند، می‌توان از آن‌ها برای تثبیت ماسه‌های روان استفاده کرد.

Investigating the effect of Lignocellulose Mulch on Sand Shear Strength

Introduction: As one of the most significant environmental problems in recent decades, wind erosion has caused environmental pollution throughout the world (Shojaei et al., 2019; Aliabad et al., 2019; Alipour et al., 2016).), inflicting damages to nearly 500 million hectares of land worldwide per year (equivalent to 46.4% of the worldchr('39')s degraded lands) (Rand et al., 2015). On the other hand, the presence of large areas of running sands, wind erosioninflicted damages, and problems regarding the use of oilbased mulches, highlights the necessity of using nature friendly mulches. This study, therefore, sought to investigate the effects of lignocellulosic nanomaterials and lignocellulosic micromaterials on shear strength of soft sands and to the positive and negative effects of such mulchs in that regard so that the most appropriate composition and extent of those mulchs could be identified in terms of increased shear strength of sand particles. Materials and methods: To conduct this study, a sample of sandy soil with 89% sand particles was collected from the Isfahan rsquo;s sand dunes (Rig Boland of Kashan) in the central Iran. Bagasse paste is used to make lignocellulose materials. Using blade mills and super disk mills, bagasse paste is transformed into lignocellulosic micromaterials and nanomaterials. Moreover, the Black liqueur is a paper industry rsquo;s waste that is used as an adhesive element.To investigate the effect of lignocellulose nanomaterials and lignocellulose micromaterials on soft sands rsquo; shear strength, nano and microparticles each with 0.3% concentration at three levels (2.5, 5 and 10 g/L in 0.3 m2 soil), Black liqueur with 1% concentration at the level of 10 g/L in 0.3 m2 soil, a combination of Nano lignocellulose (NL) and Black liqueur (BL) in three levels (2.5, 5 and 10 g/L at 0.3 m2 of soil), composition of Microlignocellulose (ML) and black liqueur at three levels (2.5, 5 and 10 g / L in 0.3 m2 soil), the control sample and all treatments in onelater and twolayer thickness were sprayed on the surface of the sand. Furthermore, shear blades were used to measure the adhesion of the mulches under saturated and dry conditions. Results: In saturated mode, the maximum shear strength of the doublelayer microlignocellulose was found to be 10 g/0.3m2, with the shear strength increased to 13.6 kN/m2 compared to the control sample (zero), followed by double layer microlignocellulose at 5 g/0.3m2 (8 kN/m2) level, double layer nanolignocellulose at 10 g/0.3m2 (7 kN/m2) level, and the combination of singlelayer microlignocellulose plus Black liqueur at 10 g/0.3m2 level (7 kN/m2). It was also found that the lowest shear strengths belonged to singlelayer treatments of NL (at all levels), ML (2.5 and 5 g/0.3m2), and the combination ML + BL (2.5 g/0.3m2), as well as doublelayer treatments of the combination of NL + BL (at all levels), and 2.5 g/0.3m2 ML + BL.In the dry mode, the maximum shear strength belonged to double layer NL + BL mulch at 10 g/0.3m2 level, with its shear strength increased by 39 kN/m2 compared to the control sample (zero), followed by doublelayer ML at 10 g/0.3m2 (36.33 kN/m2), and a combination of double layer ML + BL (33.33 kN/m2), respectively. The study rsquo;s findings indicated that there was no significant difference between these three types of mulches in terms of shear strength at 5% confidence level, while the results of the mean comparison between these three types of mulches and the control sample showed a significant difference in terms of shear strength (P <0.05). Table (7): Shear strength of different mulches in both saturated and dry conditions One LayerDouble Layer Black Liqueurcontrol(water) lignocelluloselignocellulose + Black Liqueurlignocelluloselignocellulose + Black Liqueur Saturationlevel2.55102.55102.55102.5510One LayerDouble Layer Nano000143167000 3.3 0.3 0Micro000.660371.33813.603.66DryNano05261422116260739 1 0 0Micro00501131143621533 Discussion and Conclusion: As mentioned above, the amount of shear strength increased in the dry mode compared to the saturation one. Therefore, it seems that the passage of time and dryness of the sandy bed have increased the efficiency and strength of the mulch. While the findings of some studies have indicated a significant correlation between the soil rsquo;s shear strength and time, other studies have proven the opposite. Moreover, this study found that the paper layer created by the spray of NL on the sand rsquo;s surface increased the resistance to sand retardation as well as surface resistance to sinking. Therefore, it appears that the morphologic structure of NL which is comprised of long holeless nano strings increased both abrasion and strengths.According to the study rsquo;s findings, the minimum amounts of shear strength belonged to the treatments of 2.5 gr/0.3m2 NL, ML, ML+BL, 5 gr/0.3m2 of singlelayer ML, the combination of NL+BL, and doublelayer BL, with the results of the mean comparison between these treatments (minimum shear strength) and the control sample proving no significant difference between them in terms of shear strength (P <0.05). The results of the study also showed that while a seemingly integrated layer had been created on the sand surface via the addition of those mulchs, limited suspensions may have prevented proper adhesion of the sand particles, leading to the easy disintegration of the particles. Therefore, it is recommended that these types of mulches be tested in the natural field first, and should they produced favorable results, be used for the stabilization of the running sands.