Experimental and Numerical Investigations into the Strength of Intact Veined Rock

Turichshev, Alexandr; Hadjigeorgiou, John

doi:10.1007/s00603-014-0690-x

Cited by 24 publications

(12 citation statements)

References 7 publications

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“…Mineral veins often have long and complex geological histories, and therefore their geometries, thicknesses, terminations and compositions are similarly complex, even at a small scale (Turichshev and Hadjigeorgiou 2014). For this set of tests, samples were cored with diameters of 50 and 70 mm.…”

Section: Samples Containing Mineral Veinsmentioning

confidence: 99%

Tensile Strength of Geological Discontinuities Including Incipient Bedding, Rock Joints and Mineral Veins

2016

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Geological discontinuities have a controlling influence for many rock-engineering projects in terms of strength, deformability and permeability, but their characterisation is often very difficult. Whilst discontinuities are often modelled as lacking any strength, in many rock masses visible rock discontinuities are only incipient and have tensile strength that may approach and can even exceed that of the parent rock. This fact is of high importance for realistic rock mass characterisation but is generally ignored. It is argued that current ISRM and other standards for rock mass characterisation, as well as rock mass classification schemes such as RMR and Q, do not allow adequately for the incipient nature of many rock fractures or their geological variability and need to be revised, at least conceptually. This paper addresses the issue of the tensile strength of incipient discontinuities in rock and presents results from a laboratory test programme to quantify this parameter. Rock samples containing visible, natural incipient discontinuities including joints, bedding, and mineral veins have been tested in direct tension. It has been confirmed that such discontinuities can have high tensile strength, approaching that of the parent rock. Others are, of course, far weaker. The tested geological discontinuities all exhibited brittle failure at axial strain less than 0.5 % under direct tension conditions. Three factors contributing to the tensile strength of incipient rock discontinuities have been investigated and characterised. A distinction is made between sections of discontinuity that are only partially developed, sections of discontinuity that have been locally weathered leaving localised residual rock bridges and sections that have been 'healed' through secondary cementation. Tests on bedding surfaces within sandstone showed that tensile strength of adjacent incipient bedding can vary considerably. In this particular series of tests, values of tensile strength for bedding planes ranged from 32 to 88 % of the parent rock strength (intact without visible discontinuities), and this variability could be attributed to geological factors. Tests on incipient mineral veins also showed considerable scatter, the strength depending upon the geological nature of vein development as well as the presence of rock bridges. As might be anticipated, tensile strength of incipient rock joints decreases with degree of weathering as expressed in colour changes adjacent to rock bridges. Tensile strengths of rock bridges (lacking marked discolouration) were found to be similar to that of the parent rock. It is concluded that the degree of incipiency of rock discontinuities needs to be differentiated in the process of rock mass classification and engineering design and that this can best be done with reference to the tensile strength relative to that of the parent rock. It is argued that the science of rock mass characterisation may be advanced through better appreciation of geological history at a site thereby improving the ...

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Section: Samples Containing Mineral Veinsmentioning

confidence: 99%

Tensile Strength of Geological Discontinuities Including Incipient Bedding, Rock Joints and Mineral Veins

2016

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“…Since the strength of a material is usually governed by the weakest portion, the large amount of pre-existing weak cementation face makes the grouted gangue more prone to fragmentation. Turichshev and Hadjigeorgiou [27] demonstrated that an intact veined rock specimen failed along a vein, as shown in Figures 11 and 12, and concluded that the weakest mechanical link in the system determines the overall strength. Along with the load and deformation of the specimens, the skeleton was first compacted, followed by stress concentration surrounding the gangue.…”

Section: Damage Patternmentioning

confidence: 98%

“…Illustration of a fracture developed in Specimen 1 (a) and in the corresponding synthetic rock mass (SRM) specimen (b), with displacement vectors shown in (c). Smooth joint contacts broken in tension (red disks) and in shear (green disks) are shown in (d) (reprinted with permission from Reference[27]). …”

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confidence: 99%

Mechanical Properties and Consolidation Performances of High-Polymer Material in Coal

Chen

2020

Energies

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Roof collapse and wall spalling in mines commonly occurred. Grouting in the rock mass of a collapsed zone is one of the most effective technologies for solving this problem. Through grouting, the rock mass of a collapsed zone can be cemented into continuous and stable blocks, and the physical and mechanical parameters of the rock mass can be significantly improved. In order to investigate the mechanical properties and damage of rock samples after the injection of a high-polymer material, we conducted uniaxial compression tests in a laboratory on grouted specimens. A high-polymer material is commonly used to address the gangue stacking that is caused by large roof collapse and wall spalling accidents in the mining face and the cracking of coal walls. Research has shown that a high-polymer material effectively solidifies gangues. The results indicate a micromechanics effect of the grouted specimens under uniaxial compression. The compressive strength, fracture propagation, damage mode, and other specimen behaviors are related to the amount of injected high-polymer materials. A high-polymer material substantially improves the mechanical strength of the prefabricated fractured coal and rock mass via strong material adhesion. The vertically- and horizontally-consolidated coal/rock masses exhibit different properties. The use of a high-polymer material results in distinct properties of the consolidated coal and rock masses.

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“…Veining can have a significant impact on the strength of jointed rock blocks (primary fragmentation), and the degree of secondary fragmentation (Jakubec 2013;Kaiser et al 2015;Turichshev & Hadjigeorgiou 2015;Bewick & Kaiser 2016). Even though vein data was flagged along rock cores, precise information (location and frequency) of veins was not available.…”

Section: Data Limitation and Assumptionmentioning

confidence: 99%

Presence of natural fracture as an indicator of operational difficulty for cave operations

Munkhchuluun¹,

Elmo²,

Nadolski³

et al. 2018

Proceedings of the Fourth International Symposium on Block and Sublevel Caving

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Cave mining methods are becoming the methods of choice due to their potential to extract ore from large low-grade deposits at depth at production rates comparable to open pit mines. However, the high upfront capital related to the degree of development and time lag before production require detailed planning and reliable studies to cope with the associated risks. One important geotechnical issue is managing rock mass fragmentation that affects both project value and safety. Both the scale of the problem and the lack of direct access to the rock mass at project evaluation and design stages make characterisation and accurate prediction of rock mass fragmentation a very difficult task. In this context, caving geomechanics is still largely an empirically based exercise. The discrete fracture network (DFN) approach uses fracture data collected from mapping of boreholes and rock exposures. The DFN approach was used to generate an in situ fragmentation model for the New Afton B1 Cave. The volumetric fracture intensity value (P32) is used as an indicator of the rock mass's structural character, and provides a direct link to rock mass fragmentation. Major structures were included in the model and the spatial variability of the fracture intensity was analysed to derive a geostatistical model of rock mass fragmentation. The fragmentation 'block model' was then superimposed onto New Afton's PCBC TM historical draw schedule model in an attempt to report blocks, representing the in situ fragmentation to drawpoint with respect to historical logs of hang-up event frequency, which also can refer back to height of draw (HOD). It was found that the influence of natural fractures diminishes gradually as the HOD increases. This is largely due to comminution in the draw column. The results showed that the model could identify areas of high hang-up events during initial draw prior to the column reaching maturity with respect to fragmentation.

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Experimental and Numerical Investigations into the Strength of Intact Veined Rock

Cited by 24 publications

References 7 publications

Tensile Strength of Geological Discontinuities Including Incipient Bedding, Rock Joints and Mineral Veins

Tensile Strength of Geological Discontinuities Including Incipient Bedding, Rock Joints and Mineral Veins

Mechanical Properties and Consolidation Performances of High-Polymer Material in Coal

Presence of natural fracture as an indicator of operational difficulty for cave operations

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