Ergün TUNCAY, Reşat ULUSAY, Hidehiko WATANABE, Hisataka TANO, Ömer AYDAN, Erdoğan YÜZER

Akustik Emisyon (AE) tekniği: 2- AE tekniğiyle Türkiye'de arazi gerilmelerinin belirlenmesi konusunda bir ön inceleme

Arazi (in-situ) gerilmelerinin büyüklüklerinin, yönelimlerinin ve dağılımlarının belirlenmesi, yeraltı açıklıklarının duraylılığı, destek sistemlerinin tasarımı, kaya patlamalarının önceden kestirimi ve şev duraylılığı gibi mühendislik uygulamalarının yanı sıra, depremlerin yorumlanması açısından da oldukça büyük bir önem taşımaktadır. Arazi gerilmelerinin belirlenmesi için önerilen kuramsal yaklaşımların yanı sıra, hidrolik çatlatma, gerilim boşaltma ve gerilim dengeleme gibi arazi deney yöntemleri bulunmaktadır. Ayrıca, maliyeti daha düşük olan Akustik Emisyon (yayılma) (AE) yöntemi, küresel konumlama sistemine (GPS) dayanan yöntem ve fay çiziklerinden gerilmeyi belirleme yöntemi gibi yöntemlerden de yararlanılmaktadır. Diğer arazi deney yöntemlerine göre daha pratik ve maliyetinin düşük olması, ayrıca bazı yöntemlerdeki sınırlamaları içermemesi nedeniyle, AE tekniğinin kullanımıyla ilgili çalışmalar özellikle son on yılda Japonya ve ABD'de yaygınlaşmıştır. Türkiye'de çok sayıda büyük kaya mühendisliği yapısı bulunmasına rağmen, gerilmelerin yerinde belirlenmesi için gerçekleştirilen arazi deneyi yok denecek kadar azdır. Bu çalışmada öncelikle, AE tekniğinin gerilmelerin belirlenmesinde kullanımı anlatılmış, yaygın olarak kullanılan diğer yöntemlerle kısaca karşılaştırılmış, yöntemden elde edilen sonuçları etkileyen faktörler ve yöntemin sınırlamaları tartışılmıştır. Ayrıca, Türkiye'deki çeşitli açık işletmelerden, tünel, yeraltı işletmeleri ve taş ocaklarından elde edilmiş kaya bloklarından laboratuvarda alınan yönlü karotlar üzerinde yapılan AE deneylerinden elde edilen bulgular sunularak yorumlanmıştır. Elde edilen sonuçlara göre, Türkiye'de farklı yerler için AE tekniğinden belirlenen düşey gerilmelerin bazıları, kuramsal olarak hesaplanan örtü tabakası gerilmeleriyle benzerlik gösterirken, bazıları oldukça farklı çıkmıştır. Ayrıca AE yöntemiyle Türkiye'deki ölçüm yerleri için belirlenen ortalama yatay gerilmelerin düşey gerilmelere oranları, dünyanın çeşitli yerlerinde yapılan yerinde deneylerden elde edilen sonuçların alt sınırına yakın konumda yer almıştır.

Acoustic Emission (AE) technique: 2 - A preliminary investigation on the determination of in-situ stresses by AE technique in Turkey

Determination of the magnitude, orientation and distribution of in-situ stresses has a prime importance in engineering applications such as stability of underground openings, prediction of rock bursts, slope stability, and also for the interpretation of earthquakes. In addition to theoretical approaches for the determination of in-situ stresses, some in-situ testing methods such as hydraulic fracturing, overcoring and stress compensating method are being employed. Besides, the cheaper techniques including Acoustic Emission (AE) method, the methods based on global positioning system(GPS) and fault striations are also utilized. Because the AE method is cheaper and simpler when compared to other in-situ testing methods and does not have some limitations which are involved by some other methods, investigations on this method became more common particularly in the last decade in USA and Japan. Although many rock engineering structures exist in Turkey, there is no considerable amount of in-situ stress measurements. In this study, firstly the use of AE technique for in-situ stress measurements, comparison of the technique with the other commonly employed methods, the factors affecting the results from AE measurements and limitations of the method are briefly discussed. In addition, the results of the AE tests obtained from the orien-ted core specimens, which are extracted from the blocks sampled from various open pit and underground mines, tunnels and quarries in Turkey, are presented and assessed. The results reveal that there are some similarities between the vertical stresses determined from the AE technique and theoretically calculated overburden stresses by using depth and unit weight of the rocks, while some of them show evident differences. In addition, the ratios of average horizontal and vertical stresses calculated from the AE measurements in Turkey take place at the lo-wer bound of those obtained from in-situ stress measurement at the different parts of the world.

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