تاثیر جانمایی ژئوگرید در بهسازی خاک مخلوط ماسه- رس جهت استفاده در لایه های روسازی

نوع مقاله : علمی - پژوهشی

نویسندگان

1 دانش آموخته کارشناسی ارشد، گروه زمین شناسی مهندسی، واحد اهر، دانشگاه آزاد اسلامی، اهر، ایران

2 استادیار، گروه مهندسی عمران، واحد تبریز، دانشگاه آزاد اسلامی، تبریز، ایران

چکیده

تثبیت خاک روشی است که در راهسازی به منظور بهبود توانایی باربری مصالح بکار می‌رود. در حالت کلی، تثبیت خاک عبارت است از بهبود و اصلاح خواص فیزیکی مصالح برای تامین تعدادی اهداف از قبل تعیین شده هست. بهسازی خاکها در حالت کلی به دو صورت شیمیایی و مکانیکی انجام می‌شود. استفاده از مصالح ژئوسنتتیک جهت اصلاح خاک ها در دیوار حائل، خاکریزها، زهکشی بهره گرفته می‌شود. استفاده از ژئوگریدها در بسیاری از کاربردهای مهندسی و روسازی راه یک روش موثر در اصلاح خاک به شمار می‌آید. اضافه شدن رس یا سیلت به ماسه در درصدهای مختلف می‌تواند بطور اساسی رفتار ماتریس ماسه و رس را تغییر دهد. هدف اصلی از تحقیق حاضر، بررسی آزمایشگاهی تاثیر جانمایی لایه ژئوگرید و تعداد آن ها در میزان توانایی باربری و مقاومت برشی خاکهای ماسه ای و رسی منطقه باراندوز هست. در این مطالعه خاک ماسه‌ای مورد استفاده با خاک رسی با درصدهای (25، 50 و 75) مخلوط گردیده است. تاثیر ژئوگرید به دو صورت مطالعه گردید: مرحله اول یک لایه در قسمت میانی مصالح قرارداده شده و در مرحله دوم دو لایه در فاصله برابر از یکدیگر استفاده شده و تاثیر آنها در بهبود خصوصیات ژئوتکنیکی مورد بررسی قرار گرفت. جهت انجام تحقیق از آزمون‌های آزمایشگاهی نسبت باربری کالیفرنیا(CBR) و برش مستقیم در هر دو حالت خشک و اشباع براساس استاندارد ASTM بهره گرفته شده و میزان درصد تورم در خاک های ریزدانه اشباع اندازه ‌گیری شده است. نتایج حاصل از تحقیق نشان می‌دهد که حالت بهینه قرارگیری ژئوگرید، یک لایه و در قسمت میانی مصالح هست. زیرا این شرایط باعث بهبود میزان تراکم پذیری مصالح، افزایش میزان توانایی باربری با توجه به نتایج CBR، مقاومت برشی و کاهش میزان تورم در خاکهای اشباع حاوی ریزدانه می‌گردد.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Effect of Geogrid Locating in Improvement of Sand-Clay Mixtures Applied in Pavement Layers

نویسندگان [English]

  • Ferzaneh Eslami Tabar 1
  • Rouzbeh Dabiri 2
1 Department of Engineering Geology, Ahar Branch, Islamic Azad University, Ahar, Iran
2 Department of Civil Engineering, Tabriz Branch, Islamic Azad University, Tabriz, Iran
چکیده [English]

Soil improvement a method is used for increasing bearing capacity of materials applied in pavement layers. Stabilization generally performed based on two methods chemically and mechanically. Currently geosynthetic materials are used for soil improvement in retaining walls and earth fall. The application of geogrid layers is one of the effective method in many engineering projects and pavement design for soil improvement. Increase of clay or silt content in sand in various percent can basically change geotechnical behavior of mixture. Main aim of this research is experimental study of georid layers locating and number of them effects on bearing capacity and shear strength of sandy and clayey soils from Barandouz area. In this study sandy soil mixed with clay in 25, 50 and 75%. The effect of geogrids on geotechnical properties of specimens studied in two positions: first a geogrid embedded in the middle of materials and second two geogrids by equal depth from each other used in soils. For evaluating geotechnical behavior of sand-clay mixtures California bearing ratio (CBR) and Direct shear tests performed based on ASTM in both dry and saturate conditions. Also, percent of swelling in fines content saturated soils assessed. Results showed that in unreinforced specimens with increasing fines content in bearing capacity and geotechnical properties decreased. Then, with embed a geogrid layer in middle part of specimens compared to two geogrid layers value of sand skeleton void ratio decreased and maximum dry unit weight increased and at that time bearing capacity and shear strength of materials in both dry and saturate condition improved. Also, swelling percent of fines content soils with embed a geogrid layer significantly as compared to an unreinforced decreased. Therefore, it is recommended application of one geogrid layer in sand-clay mixtures is optimum for design subgrade and sub base layers in pavement

کلیدواژه‌ها [English]

  • California bearing ratio (CBR) test
  • Clay-sand mixtures. Direct shear test
  • Geogrid
  • pavement design
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