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    Öğe
    Kayalarda Mikro Çatlaklanma Sürecine Bağlı Deformasyon Evriminin Sayısal Analizi
    (2023) Göğüş, Özge Dinç; Avşar, Elif; Develi, Kayhan; Çalık, Ayten
    Gerilmeye maruz kalan bir kayanın yenilme ve deformasyon karakteri mikro ölçekteki çatlaklanma sürecine bağlıdır. Bu sürecin nasıl evrildiğinin anlaşılması konusunda farklı laboratuvar ve analitik yöntemler kullanılmaktadır. Bu çalışmada söz konusu yöntemlere bir alternatif olarak mikro çatlaklanma sürecinin sayısal modelleme tekniği ile tespit edilebilirliği araştırılmıştır. İgnimbirit, mermer ve diyabaz olmak üzere üç farklı kaya türü üzerinde yapılan laboratuvar deneylerinden elde edilen makro mekanik parametreler, ayrık elemanlar yöntemine (DEM) dayalı sayısal kaya modellerinin kalibrasyonunda kullanılmıştır. Sonuçlar incelendiğinde model tahminleri ile laboratuvar verilerinin uyumlu olduğu belirlenmiş ve bu durum sayısal çatlaklanma analizlerinin kaya ortamını temsil edecek şekilde yürütülebileceğini göstermiştir. Laboratuvar deneylerinin simülasyonlarında, sıkışma gerilmesi altındaki model örneklerde mikro çatlaklanmanın başladığı (?ci) ve ilerleyerek biriktiği (?cd) kritik eşik gerilme seviyeleri tespit edilmiştir. Bu gerilme seviyeleri sırasıyla ignimbirit için ?ci = 25 MPa ve ?cd = 37 MPa; mermer için ?ci = 21 MPa ve ?cd = 30 MPa ve diyabaz için ?ci = 38 MPa ve ?cd = 55 MPa olarak belirlenmiştir. Tüm kaya modellerinde mikro çatlaklanma çekme mekanizması tarafından kontrol edilirken her üç kaya türü de gevrek bir davranış sergilemektedir. Elde edilen tüm veriler, kayalardaki mikro çatlaklanma sürecinin araştırılmasında DEM tabanlı sayısal modelleme tekniğinin diğer yöntemlere alternatif olarak güvenli bir şekilde kullanılabileceğini göstermektedir.
  • [ X ]
    Öğe
    Numerical Analysis of Rock Deformation Evolution Regarding Microcracking Process
    (Hacettepe Universitesi Yerbilmleri, 2023) Göğüş, Özge Dinç; Avşar, Elif; Develi, Kayhan; Çalık, Ayten
    The failure and deformation characteristics of rock under stress are controlled by microcracking process. There are various laboratory and analytical methods for understanding the evolution of this phenomenon. In this study, the applicability of the numerical modeling technique for detecting the microcracking process is investigated as an alternative method among the other techniques. Macro mechanical parameters derived from the laboratory tests, performed on three different rock types such as ignimbrite, marble, and diabase are used in the calibration of the numerical rock models which are generated based on the discrete element method (DEM). According to the results, model predictions and laboratory measurements are in good agreement that verifying cracking analysis can be performed as being representative of the rock domain in the numerical platform. During the simulations of laboratory tests, the initiation (?ci) and propagation (?cd) stress thresholds of microcracking are determined in the model samples under compressive loading. These stress levels are ?ci = 25 MPa and ?cd = 37 MPa for ignimbrite, ?ci = 21 MPa and ?cd = 30 MPa for marble, and ?ci = 38 MPa and ?cd = 55 MPa for diabase, respectively. Microcracking in all rock models is controlled by extensional mechanisms, and all rock types present brittle behavior. Overall, our insights show that the numerical modeling technique based on DEM can be used reliably as an alternative methodology to the other techniques for the investigation of the microcracking process in rocks. © 2023, Hacettepe Universitesi Yerbilmleri. All rights reserved.
  • Küçük Resim
    Öğe
    Quantifying the Rock Damage Intensity Controlled by Mineral Compositions: Insights from Fractal Analyses
    (MDPI, 2023) Dinç Göğüş, Özge; Develi, Kayhan; Çalık, Ayten
    Since each rock type represents different deformation characteristics, prediction of the damage beforehand is one of the most fundamental problems of industrial activities and rock engineering studies. Previous studies have predicted the stress–strain behaviors preceding rock failure; however, quantitative analyses of the progressive damage in different rocks under stress have not been accurately presented. This study aims to quantify pre-failure rock damage by investigating the stress-induced microscale cracking process in three different rock types, including diabase, ignimbrite, and marble, representing strong, medium-hard, and weak rock types, respectively. We demonstrate crack intensity at critical stress levels where cracking initiates (σci), propagates (σcd), and where failure occurs (σpeak) based on scanning electron microscope (SEM) images. Furthermore, the progression of rock damage was quantified for each rock type through the fractal analyses of crack patterns on these images. Our results show that the patterns in diabase have the highest fractal dimensions (DB) for all three stress levels. While marble produces the lowest DB value up to σci stress level, it presents greater DB values than those of ignimbrite, starting from the σcd level. This is because rock damage in ignimbrite is controlled by the groundmass, proceeding from such stress level. Rock texture controls the rock stiffness and, hence, the DB values of cracking. The mineral composition is effective on the rock strength, but the textural pattern of the minerals has a first-order control on the rock deformation behavior. Overall, our results provide a better understanding of progressive damage in different rock types, which is crucial in the design of engineering structures.
  • [ X ]
    Öğe
    The role of mineralogical and textural complexity in the damage evolution of brittle rocks
    (Nature Portfolio, 2024) Göğüş, Özge Dinç; Avşar, Elif; Develi, Kayhan; Çalık, Ayten
    In brittle rocks, deformation is characterized by the initiation and propagation of cracks at both microscale and mesoscale levels. This study explores how rock texture influences the evolution of cracking networks and progressive rock damage results under uniaxial compression. 3D discrete analyses were employed to identify the critical stresses of three different rock types. Thin sections were prepared from uniaxially loaded core samples at these stresses and crack patterns were captured under a polarizing microscope. The fractal box dimension method was used to quantitatively analyze the crack patterns for each rock type at each stress level. The novelty of this research is revealing the relationship between the development of microcrack patterns and textural properties such as mineral orientation/distribution, interlocking, crystal cleavage/hardness, and the groundmass. Results show that the cracking tendency varies with rock type at each critical stress level. Specifically, diabase exhibited the highest crack intensity, attributed to the interlocking of hard plagioclase and pyroxene crystals. Furthermore, the cleavages in pyroxenes make diabase particularly susceptible to cracking, especially when they are oriented parallel or semi-parallel to the applied load. These findings highlight that rock texture is a crucial factor influencing microcrack development, which should be considered in rock engineering applications.