Pegah DADRAS, Saeid ZARDARI, Amir SHAHKAR

FRP LİFİ İLE GÜÇLENDİRİLMİŞ SİLTLİ KUMUN KAYMA MUKAVEMETİNİN BÜYÜK ÖLÇEKLİ DİREKT KESME KUTUSU DENEYİ KULLANARAK BELİRLENMESİ

İnşaat ve geoteknik projelerinin birçoğunda saha zemininin gerekli teknik ve mekanik özelliklere sahip olmaması zeminin iyileştirilmesi gerekliliğini kaçınılmaz kılmaktadır. Zemin iyileştirme ve güçlendirme yöntemleri arasında zeminin rastgele dağılımlı lifler ile güçlendirilmesinden bahsedilebilir. Bu araştırmada, laboratuvar ortamında rastgele dağılmış FRP lifleri ile güçlendirilmiş siltli kumun kayma mukavemeti, kesme kutusu deneyi ile incelenmiştir. Büyük boyutlu numunelerin daha gerçekçi olması ve davranışları zeminin sahadaki gerçek davranışıyla daha uyumlu olması nedeniyle, çalışmada, büyük ölçekli (300*300 mm) kesme kutusu deney cihazı kullanılmıştır. Zemini güçlendirmek için 30 ve 40 mm uzunluğunda lifler kullanılmıştır. Zemin-lif karışımlarında liflerin ağırlıkça yüzdeleri %0,1, 0,2, 0,3 ve 0,4 olarak alınmıştır. Liflerin ağırlık yüzdesi, liflerin ağırlığının zeminin kuru ağırlığının oranıdır. Saf zeminin sürtünme açısı 27,7 derece ve kohezyonu 15 kPa iken, güçlendirilmiş zeminin maksimum sürtünme açısı 40,7 dereceye, kohezyon ise 18 kPa'a kadar yükselmiştir. İçsel sürtünme açıları karşılaştırıldığında %47’lik bir artış görülmektedir. Deney sonuçlarından elde edilen verilerden hareketle lif içeriğinin artmasıyla zeminin kayma mukavemetinin önce arttığı ve daha sonra azaldığı gözlemlenmiştir. Lif içeriği %0,3 ve lif uzunluğu 30 mm olan karışımlarda maksimum kayma mukavemet elde edilmiştir. Dolayısıyla çalışmada optimum lif içeriği ve lif uzunluğu sırasıyla %0,3 ve 30 mm olarak elde edilmiştir.

Anahtar Kelimeler:

Kayma Mukavemeti, FRP Lifi, Zemin Güçlendirmesi, Siltli Kum, Büyük Ölçekli Kesme Kutusu Deneyi

Determination of The Shear Strength of FRP Fiber Reinforced Silty Sand Using Large Scale Direct Shear Test

In many of the construction and geotechnical projects, the fact that the soil of the project site does not have the necessary technical and mechanical properties makes the necessity of soil improvement inevitable. Among the soil improvement and reinforcement methods, the reinforcement of the soil with randomly distributed fibers can be mentioned. In this study, the shear strength of silty sand reinforced with randomly distributed FRP fibers was investigated in the laboratory using direct shear test. A large-scale (300*300 mm) direct shear test device was used in this study, as large sized specimens are more realistic and their behavior is more compatible with the actual behavior of the soil in the field. Fibers with the lengths of 30 and 40 mm were used to reinforce the soil. The weight percentages of fibers in the soil-fiber mixtures are 0.1, 0.2, 0.3 and 0.4%. The weight percent of the fibers is the ratio of the weight of the fibers to the dry weight of the soil. While the friction angle of the pure soil was 27.7 degrees and the cohesion was 15 kPa, the maximum internal friction angle of the reinforced soil increased up to 40.7 degrees and the cohesion up to 18 kPa. Comparing the internal friction angles, an increase of 47% can be observed. Considering the test results, it was observed that the shear strength of the soil first increased and then decreased with the increase in fiber content. Maximum shear strength was obtained in mixture with a fiber content of 0.3% and a fiber length of 30 mm. Therefore, in this study, optimum fiber content and fiber length were obtained as 0.3% and 30 mm, respectively.

Keywords:

Shear Strength, FRP fiber, Soil Reinforcement, Silty Sand, Large Scale Direct Shear Test,

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