ZEMİN SIVILAŞMASINA KARŞI GELİŞTİRİLEN KISMİ DOYGUNLUĞA İNDİRGEME METOTLARI ÜZERİNE DENEYSEL ÇALIŞMA: GAZ KABARCIKLARININ DAĞILIMI

Yıl 2022, Cilt: 30 Sayı: 3, 309 - 317, 21.12.2022

Abdulhakim Zeybek

https://doi.org/10.31796/ogummf.1062953

Öz

Doymuş kumlu zeminler, deprem yükleri altında sıvılaşarak serbest saha ve yapılar üzerinde zararlı etkilere neden olabilmektedir. Yapıların güvenliğini ve kullanılabilirliğini sağlamak için zemin sıvılaşmasına bağlı hasarların azaltılması veya önlenmesi gerekmektedir. Son yıllarda ortaya çıkmış olan Kısmi Doygunluğa İndirgeme (IPS) tekniği sıvılaşmanın etkilerini azaltmada kullanılabilecek yeni bir yöntemdir. Bu çalışmada, iki farklı IPS yöntemi kullanılarak kısmi doygun hale getirilmiş kum modelleri üzerinde laboratuvar testleri gerçekleştirilmiş ve özellikle zemin içerisindeki boşluklarda suni olarak oluşturulmuş olan hava/gaz kabarcıklarının dağılımı incelenmiştir. Bu amaç doğrultusunda, hava enjekte ederek veya kimyasal madde kullanarak şeffaf pleksiglas kutu içinde kısmi doygun gevşek kum modelleri hazırlanmıştır. Farklı test aşamalarında kaydedilmiş dijital resimler yardımı ile gaz/hava kabarcıklarının zemin içindeki dağılımı gözlemlenmiştir. Ayrıca, kum modellerinin farklı noktalarına yerleştirilen toprak nem ölçüm sensörleri ile doygunluk derecesinin zamana bağlı değişimi tespit edilmiştir. Test verilerinin kapsamlı analizleri, kullanılan kimyasal maddenin su içinde reaksiyona girmesi ile zemin içinde oksijen kabarcıkları oluşturduğunu ve bu kabarcıkların yeterince üniform olarak dağıldığını göstermiştir. Aynı zamanda bu yöntem ile istenilen doygunluk derecelerinde kum modelleri hazırlanabilmiştir. Buna karşılık, zemine enjekte edilen havanın sınırlı bir akış yolunu takip ettiği gözlemlenmiş ve hava enjeksiyon tekniğinin yerçekimi etkisi altında üniform ve düşük doygunluk derecesine (%90 altı) sahip kısmi doygun kum modellerinin hazırlanmasında nispeten daha az başarılı olduğu görülmüştür.

Anahtar Kelimeler

Sıvılaşma, Kısmi Doygunluk, Hava Enjeksiyonu, Kimyasal Madde, Hidrojen Peroksit

EXPERIMENTAL INSIGHTS INTO INDUCED PARTIAL SATURATION METHODS DEVELOPED FOR LIQUEFACTION MITIGATION: DISTRIBUTION OF GAS BUBBLES

Öz

Saturated deposits of sandy soils may liquefy during an earthquake event, causing detrimental effects on the site and structures. Mitigation of liquefaction-induced damage is of the essence when the structures are expected to exceed the acceptable limits of safety and serviceability. Induced Partial Saturation (IPS) has been recently proposed as a novel liquefaction countermeasure. In the present study, several laboratory tests were conducted on partially saturated sand models to offer insights into two IPS methods, paying more attention to the distribution of air/gas bubbles entrapped in pore spaces. For this purpose, loose deposits of partially saturated sand were prepared in transparent plexiglass boxes either injecting air or using a chemical substance. Digital images were recorded at different stages of the tests, which provided an opportunity to visualize the distribution of gas/air bubbles. Furthermore, moisture sensors were placed at different locations of sand models, allowing to capture the variation of the degree of saturation with time. Comprehensive analyses of the test data suggested that oxygen bubbles were generated through a reaction between water and chemical substance, and the distribution of oxygen bubbles was sufficiently uniform across the sand models. This method also allowed the preparation of sand models at the desired degrees of saturation. On the contrary, at 1-g injected air was observed to flow through a path of less resistance, and this technique was comparatively less successful in preparing sand models with uniformly distributed air bubbles and at lower degrees of saturation (i.e., below 90%).

Anahtar Kelimeler

Liquefaction, Partial Saturation, Air Injection, Chemical Substances, Hydrogen Peroxide

Kaynakça

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