Petrographic features as an effective indicator for the variation in strength of granites

Sajid, Muhammad; Coggan, John; Arif, Mohammad; Andersen, Jens C.Ø.; Rollinson, Gavyn

doi:10.1016/j.enggeo.2016.01.001

Cited by 85 publications

(40 citation statements)

References 137 publications

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“…They argued that the mechanical properties of granites are linearly correlated with quartz and feldspar content, respectively, positively and negatively. However, this conclusion is in direct contrast to the work by Yilmaz et al [ 11 ], Sousa [ 16 ], and Sajid et al [ 17 ]. Sousa [ 16 ] evaluated the mechanical behaviors of different Portuguese granites based on their petrographic characteristics, including grain size, quartz fissuration, mineral deterioration, and the contacts between quartz and other mineral groups.…”

Section: Introductioncontrasting

confidence: 92%

Investigation of the Quasi-Brittle Failure of Alashan Granite Viewed from Laboratory Experiments and Grain-Based Discrete Element Modeling

et al. 2017

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Granite is a typical crystalline material, often used as a building material, but also a candidate host rock for the repository of high-level radioactive waste. The petrographic texture—including mineral constituents, grain shape, size, and distribution—controls the fracture initiation, propagation, and coalescence within granitic rocks. In this paper, experimental laboratory tests and numerical simulations of a grain-based approach in two-dimensional Particle Flow Code (PFC2D) were conducted on the mechanical strength and failure behavior of Alashan granite, in which the grain-like structure of granitic rock was considered. The microparameters for simulating Alashan granite were calibrated based on real laboratory strength values and strain-stress curves. The unconfined uniaxial compressive test and Brazilian indirect tensile test were performed using a grain-based approach to examine and discuss the influence of mineral grain size and distribution on the strength and patterns of microcracks in granitic rocks. The results show it is possible to reproduce the uniaxial compressive strength (UCS) and uniaxial tensile strength (UTS) of Alashan granite using the grain-based approach in PFC2D, and the average mineral size has a positive relationship with the UCS and UTS. During the modeling, most of the generated microcracks were tensile cracks. Moreover, the ratio of the different types of generated microcracks is related to the average grain size. When the average grain size in numerical models is increased, the ratio of the number of intragrain tensile cracks to the number of intergrain tensile cracks increases, and the UCS of rock samples also increases with this ratio. However, the variation in grain size distribution does not have a significant influence on the likelihood of generated microcracks.

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Section: Introductioncontrasting

confidence: 92%

Investigation of the Quasi-Brittle Failure of Alashan Granite Viewed from Laboratory Experiments and Grain-Based Discrete Element Modeling

et al. 2017

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“…The different grain size of the porphyritic and two‐mica granite observed in the deep Soultz reservoir could also affect their mechanical properties. Experimental studies (e.g., Sajid et al, ) reveal that, in a massive granite, the mean grain size of main rock forming minerals has a negative effect on matrix strength of the rock. The greater number of borehole breakout occurrence and the wider breakout geometry in the two‐mica granite compared to the porphyritic granite section (Meller, Sahara, & Kohl, ) is consistent with a reduction of the rock strength as suggested by Haimson and Chang ().…”

Section: Synthesis Of Results With Complementary Calcimetry Investigamentioning

confidence: 99%

Is There a Link Between Mineralogy, Petrophysics, and the Hydraulic and Seismic Behaviors of the Soultz‐sous‐Forêts Granite During Stimulation? A Review and Reinterpretation of Petro‐Hydromechanical Data Toward a Better Understanding of Induced Seismicity and Fluid Flow

Meller

Ledésert

2017

JGR Solid Earth

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In the framework of the European Soultz‐sous‐Forêts enhanced geothermal system (EGS) in Alsace, France, 20 years of scientific and preindustrial tests had to be performed before the site began production of electricity in 2008. Stimulation tests were designed to enhance the permeability because most of the numerous natural fractures that crosscut the granite body were sealed by secondary minerals that crystallized as an effect of the circulation of local hot brines. The deep‐seated granitic reservoir is located between 4,500 and 5,000 m depths. Hydraulic stimulations were conducted in the four deep wells (GPK1, GPK2, GPK3, and GPK4) inducing different microseismic event patterns, which cannot be explained by tectonic structures alone. In the present work, we provide a review of the hydraulic tests and reinterpret them in the light of mineralogical data obtained along the boreholes. A clear relationship appears between mineralogy (mainly clay and calcite content) and the petrophysical, mechanical, and hydraulic behaviors of the rock mass. High calcite contents are correlated with an abundance of clay minerals, low Young's modulus, low magnetic susceptibility, and variation in spectral gamma ray. Microearthquakes are generated in the fresh granite zones, while clay and calcite‐rich zones, linked with hydrothermal alteration, might behave aseismically during hydraulic stimulations. These findings highlight the importance of a detailed knowledge of the petrography of a reservoir to conduct an effective stimulation while keeping the seismic hazard at a minimum.

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“…Several researchers have studied the effect of mineralogical composition (primary and secondary phases) on the engineering properties of rocks. Many of them have dealt with the influence of primary minerals, such as biotite, quartz and K-feldspar on the mechanical properties of volcanic and granitic rocks, presenting no relationships between these primary minerals of the investigated rocks and their mechanical properties [8,11,53,54], while others have studied the negative influence of weathering/alteration on the engineering behavior of the tested rocks [5,[22][23][24]55]. The generally lower hardness of the secondary minerals relative to the primary relics accompanied by new textures result in differential engineering behaviors, thus contributing to the weakness and easier deterioration of the rocks under stress and subsequently their gradually diminished in-service performance.…”

Section: Discussionmentioning

confidence: 99%

The Influence of the Mineralogical Composition of Ultramafic Rocks on Their Engineering Performance: A Case Study from the Veria-Naousa and Gerania Ophiolite Complexes (Greece)

et al. 2018

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This case study investigates the influence of the mineralogical composition of ultramafic rocks derived from two ophiolite complexes from Greece (Veria-Naousa and Gerania) on their mechanical, physical and physicochemical properties. The investigated lithologies include lherzolite, harzburgite, dunite and olivine-orthopyroxenite with variable degrees of alteration. The ratio of secondary minerals to primary minerals (SEC/PR) of the studied ultramafic rocks shows good correlations with their physical, physicochemical and mechanical properties, suggesting that alteration has a negative effect on the engineering performance of the ultramafic rocks. Among the secondary minerals, serpentine plays the most critical role in determining the moisture content, the total porosity and hence the soundness of the host rocks, due to its phyllosilicate structure, which allows more water/solutions to be captured. The high percentage of serpentine creates surfaces of weakness, and as a result, it decreases the rock strength. The low microtopography of highly serpentinized rocks results in their reduced mechanical performance.

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Petrographic features as an effective indicator for the variation in strength of granites

Cited by 85 publications

References 137 publications

Investigation of the Quasi-Brittle Failure of Alashan Granite Viewed from Laboratory Experiments and Grain-Based Discrete Element Modeling

Investigation of the Quasi-Brittle Failure of Alashan Granite Viewed from Laboratory Experiments and Grain-Based Discrete Element Modeling

Is There a Link Between Mineralogy, Petrophysics, and the Hydraulic and Seismic Behaviors of the Soultz‐sous‐Forêts Granite During Stimulation? A Review and Reinterpretation of Petro‐Hydromechanical Data Toward a Better Understanding of Induced Seismicity and Fluid Flow

The Influence of the Mineralogical Composition of Ultramafic Rocks on Their Engineering Performance: A Case Study from the Veria-Naousa and Gerania Ophiolite Complexes (Greece)

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