Contribution of fractal dimension theory into the uniaxial compressive strength prediction of a volcanic welded bimrock
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ORIGINAL PAPER
Contribution of fractal dimension theory into the uniaxial compressive strength prediction of a volcanic welded bimrock Elif Avşar 1 Received: 7 April 2019 / Accepted: 12 March 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract This study was carried out on Sille agglomerate which is a typical volcanic welded bimrock. Two precious historical monuments, Koimesis Tes Panagias Church and Sekili hill settlement carved in Sille agglomerate, have maintained their stability without any support for centuries although suffering from weathering and various stability problems. However, due to its heterogeneity and sampling difficulties, the overall strength of Sille agglomerate has not been investigated yet. This paper presents the relationships between fragmentation fractal dimension (DF), fractal dimension of rough block surfaces (DR), number of blocks (BN), and volumetric block proportion (VBP) and the overall uniaxial compressive strength (UCS) of the Sille agglomerate. By using these properties as inputs, three statistically significant empirical models were developed for estimating the UCS of the Sille agglomerate. The results revealed that the DF and DR may be good predictors to estimate the UCS of welded volcanic bimrocks, and defining the properties of blocks by means of fractal theory provides significant contribution to the estimation of the UCS. It is observed that the failure planes in the core samples predominantly pass through the boundaries between matrix and blocks, and such behavior may indicate that the weakest component of the Sille agglomerate is boundaries. Accordingly, the UCS decreases due to the high DR values which create more or further weakest zones in the bimrocks. Finally, it is concluded that the negative correlation between the UCS and the VBP was attributed to increase of the DR due to the increase of the VBP. Keywords Bimrock . Fractal dimension . Area to perimeter method . Strength . Agglomerate
Introduction It is widely known that the determination of strength and deformation properties of heterogeneous and geologically complex rock masses such as pyroclastic rocks, melanges, fault breccias, lithified colluviums, and sheared serpentines has been highly challenging and their estimation have increasingly been studied for the last few decades. These rock masses were called as “bimrocks” (contraction of block-in-matrix rocks) for the first time by Medley (1994), and are traditionally composed of competent rock blocks and relatively weak fine-grained matrix. Sufficient strength and/or stiffness contrast (such as the ratio of uniaxial compressive strength (UCS) of blocks to those of matrix have to be greater than 1.5) is
* Elif Avşar [email protected] 1
Department of Geological Engineering, Konya Technical University, Konya, Turkey
necessary for a block-in-matrix rock mass to be considered as a bimrock (Lindquist 1994; Medley 1994). Besides, Kahraman and Alber (2006) and Kahraman et al. (2008) studied fault breccias from Germany and Turkey having bloc
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