An approach to predict the length-to-diameter ratio of a rock core specimen for uniaxial compression tests

Tuncay, Ergün; Özcan, Nazlı Tunar; Kalender, Aycan

doi:10.1007/s10064-019-01482-6

Cited by 20 publications

(5 citation statements)

References 14 publications

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“…Hawkes and Mellor 1970), it is also recommended by the ISRM that cylindrical samples should have a length to diameter ratio of 2.5 to 3. Mogi (2007) found that the uniaxial compressive strength of cylindrical samples (of granite, dolomite, and trachyte) increases at length to diameter ratios above 2.5 (see also Tuncay et al 2019), and that the influence of this ratio on compressive strength decreased when the samples were deformed under a confining pressure. Due to the paucity of data of this type, especially for volcanic rocks, we provide new experiments, described in the Appendix, designed to explore the influence of the length to diameter ratio on the uniaxial compressive strength of a dry porous trachyandesite.…”

Section: Studying Mechanical Behaviour and Failure Mode In The Laboratorymentioning

confidence: 99%

The mechanical behaviour and failure modes of volcanic rocks: a review

2021

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The microstructure and mineralogy of volcanic rocks is varied and complex, and their mechanical behaviour is similarly varied and complex. This review summarises recent developments in our understanding of the mechanical behaviour and failure modes of volcanic rocks. Compiled data show that, although porosity exerts a first-order influence on the uniaxial compressive strength of volcanic rocks, parameters such as the partitioning of the void space (pores and microcracks), pore and crystal size and shape, and alteration also play a role. The presence of water, strain rate, and temperature can also influence uniaxial compressive strength. We also discuss the merits of micromechanical models in understanding the mechanical behaviour of volcanic rocks (which includes a review of the available fracture toughness data). Compiled data show that the effective pressure required for the onset of hydrostatic inelastic compaction in volcanic rocks decreases as a function of increasing porosity, and represents the pressure required for cataclastic pore collapse. Differences between brittle and ductile mechanical behaviour (stress-strain curves and the evolution of porosity and acoustic emission activity) from triaxial deformation experiments are outlined. Brittle behaviour is typically characterised by shear fracture formation, and an increase in porosity and permeability. Ductile deformation can either be distributed (cataclastic pore collapse) or localised (compaction bands) and is characterised by a decrease in porosity and permeability. The available data show that tuffs deform by delocalised cataclasis and extrusive volcanic rocks develop compaction bands (planes of collapsed pores connected by microcracks). Brittle failure envelopes and compactive yield caps for volcanic rocks are compared, highlighting that porosity exerts a first-order control on the stresses required for the brittle-ductile transition and shear-enhanced compaction. However, these data cannot be explained by porosity alone and other microstructural parameters, such as pore size, must also play a role. Compactive yield caps for tuffs are elliptical, similar to data for sedimentary rocks, but are linear for extrusive volcanic rocks. Linear yield caps are considered to be a result of a high pre-existing microcrack density and/or a heterogeneous distribution of porosity. However, it is still unclear, with the available data, why compaction bands develop in some volcanic rocks but not others, which microstructural attributes influence the stresses required for the brittle-ductile transition and shear-enhanced compaction, and why the compactive yield caps of extrusive volcanic rocks are linear. We also review the Young’s modulus, tensile strength, and frictional properties of volcanic rocks. Finally, we review how laboratory data have and can be used to improve our understanding of volcanic systems and highlight directions for future research. A deep understanding of the mechanical behaviour and failure modes of volcanic rock can help refine and develop tools to routinely monitor the hazards posed by active volcanoes.

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Section: Studying Mechanical Behaviour and Failure Mode In The Laboratorymentioning

confidence: 99%

The mechanical behaviour and failure modes of volcanic rocks: a review

2021

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“…One of the most complex research study related to this matter was published by Brown (1980, 1997). Further investigations were elaborated in papers by Hawkins (1998), Yoshinaka et al (1988), Letko et al (1988), Thuro et al (2001), Labaš and Miklúšová (2004), Kogure et al (2005), Çobanoğlu and Çelik (2008), Durmeková and Ondrášik (2012), Jamshidi et al (2014), Jamshidi et al (2015, Al-Rkaby and Alafandi (2015), Kaklis et al 2015) and Tuncay et al (2019).…”

Section: Discussionmentioning

confidence: 99%

Influence of Specimen Size and Shape on the Uniaxial Compressive Strength Values of Rocks

Durmekova

Bednařík

Dikejová

et al. 2021

Preprint

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The most significant factors affecting the results of Uniaxial Compressive Strength (UCS) test are the size, slenderness ratio h/d (ratio of height to diameter), and the shape of the rock specimen. The proposed experimental study shows the variable impact of these parameters on UCS values by implementing several lithological types. Standard strength tests were performed on four lithological types: granodiorite, limestone, sandstone and andesite. Cylindric and cube-shaped test specimens of different sizes were prepared from each rock. Cylindric specimens with diameter 20 mm, 35 mm, 50 mm and 70 mm with height to diameter ratio of 1:1 and 2:1, and cubic and prismatic specimens with an edge dimension of 50 mm were tested and analyzed. Obtained results of strength tests confirmed a high variability of current research opinions on how the size and shape of specimens influence the strength values of rocks. The study revealed the impossibility of conclusive correlations between the UCS and specimens to be generally applicable for all lithological types. Of the observed effects on the strength, the aspect of the specimen slenderness ratio was the most pronounced on all studied rocks.

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“…Scholars have carried out a large number of experimental studies on the rock size effect. Weibull [5] proposed the strength theory of rock-like materials based on statistical Processes 2022, 10,1974 2 of 20 theory and believed that the ultimate strength of rock-like materials could be determined by the integral of its volume and the statistical distribution function. Bazant [6] studied and analyzed the size effect with the help of fracture mechanics and elaborated on the influence of the size effect on the strength of brittle materials from the theoretical perspective.…”

Section: Introductionmentioning

confidence: 99%

“…To sum up, scholars at home and abroad have made many achievements in this field [5][6][7][8][9]. However, the following questions about the rock size effect remain to be further explored: (1) at present, the size effect research is mainly aimed at the complete rock specimen [10,11], and less studied is the size effect of fractured specimens. Coal mine surrounding rock is affected by sedimentation, resulting in weak strength and the development of joints and fractures [12][13][14][15].…”

Section: Introductionmentioning

confidence: 99%

Preliminary Study on Size Effect of Fractured Rock Mass with Sand Powder 3D Printing

et al. 2022

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The size effect has a significant effect on the mechanical behavior of rock, thereby fundamentally influencing the stability of rock excavations. The main challenge associated with the experimental research on the size effect of fractured rock mass lies in the difficulty of specimen preparation to represent the influence of size and fracture on the mechanical behavior of the rock material. In order to preliminarily explore the feasibility of 3D printing technology in the field of rock mechanics, fractured rock specimens of different sizes and different fracture characteristics were produced using sand powder 3D printing technology. The uniaxial compression test was combined with the digital image correlation method (DIC) technology to study the influence of the size effect on the mechanical properties and deformation and failure of different fractured specimens. The research finds that: (1) The elastoplastic mechanical characteristics of the sand powder 3D printed specimens are similar to soft rock. Specimen size and fracture angle have significant effects on the mechanical properties of specimens. Under different fracture conditions, the uniaxial compressive strength (UCS) and Elasticity Modulus of sand powder 3D specimens should be decreased with the increase of the specimen size, and the size effect has different influences on the specimens with different fracture characteristics. (2) Under different fracture conditions, the crack initiation position and failure mode of specimens of various sizes are affected by the fracture inclination to varying degrees. (3) The size effect of fractured rock mass is closely related to the defect level inside the rock mass. The size effect originates from the heterogeneity inside the material. The research results verify the feasibility of applying sand powder 3D printing technology to study the size effect of fractured rock masses and provide an innovative test method for the size effect test study. Preliminary exploration of the size effect of fractured rock masses provides a powerful reference for related research in this field. The study proves the feasibility of applying sand powder 3D printing technology in similar rock mechanics tests and contributes to understanding the size effect of a fractured rock mass.

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An approach to predict the length-to-diameter ratio of a rock core specimen for uniaxial compression tests

Cited by 20 publications

References 14 publications

The mechanical behaviour and failure modes of volcanic rocks: a review

The mechanical behaviour and failure modes of volcanic rocks: a review

Influence of Specimen Size and Shape on the Uniaxial Compressive Strength Values of Rocks

Preliminary Study on Size Effect of Fractured Rock Mass with Sand Powder 3D Printing

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