• The Journal of Engineering Geology
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• v.23 no.4
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• pp.341-352
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• 2013

The physical and mechanical properties of red shale and black shale exposed in the Daegu area were investigated in tests conducted to determine unit weight, absorption ratio, porosity, ultrasonic velocity, unconfined compressive strength, point load strength, slake durability index, and deterioration characteristics. XRD, XRF, and SEM analyses were also performed on the shale specimens. While the unit weights of the two shales were similar, the absorption ratio and porosity were higher in the red shale than in the black shale. Despite the higher porosity of the red shale, the ultrasonic velocity, compressive strength, and point load strength were higher in the red shale, which is an unexpected result that may be due to the presence of fine laminations in the black shale. The deterioration rate, as determined from the point load strength and the slake durability index, increased with increasing immersion time and with the acidity of the immersion liquid. The deterioration rate was higher for the red shale than for the black shale because of the higher porosity of the former.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.7
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• pp.3296-3301
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• 2011

The Porous pavement gains popularity because of several benefits. It is to minimize hydro-planning condition, spraying condition, and splash to increase friction resistance, and decrease noise. Also, other studies showed that it is important to have appropriate porosity to reduce noise and water flush. The purpose of this study is an evaluation on the mechanical properties of asphalt pavements for surface course. In this study the specimen was manufactured using the Gyratory compactor in order to compact the strengthened surface course that involved the two-layer pavement. This study is conducted by using Marshall stability test(KS F 2377), Impact resonance test, Schmidt hammer test(KS F 2730), and the Uniaxial compression test(KS F 2314). Using the Uniaxial compression test and Schmidt hammer test, the values of compressive strength and bearing capacity were measured, and the modulus of elasticity for each specimen was respectively measured using the Uniaxial compression test, Impact Resonance test.

• Tunnel and Underground Space
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• v.6 no.1
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• pp.1-9
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• 1996

Pocheon granite specimens were thermally treated with cycles of predetermined temperatures ranging 2$0^{\circ}C$ to $600^{\circ}C$. Characterization of thermally-induced microcracks were carried out using optical microscopy and their effect on the various physical & mechanical properties were studied. Generally. uniaxial compressive strength, Young's modulus, Poisson's ratio, elastic wave velocity and specific gravity were found to decrease with increasing temperature. From 30$0^{\circ}C$ upwards, negative lateral strains were observed, which resulted in negative Poisson's ratio. Dynamic Young's modulus and Poisson's ratio were found to be generally most sensitive indicators to thermal cracking.

• Tunnel and Underground Space
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• v.25 no.3
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• pp.231-243
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• 2015

In this study, both in-situ stress measurements and a lot of laboratory rock tests were conducted at a metal mine in Jeongseon, Korea. The stress ratio obtained from in-situ stress measurements showed a tendency to decrease according to depth below surface and its average value was 1.10. The mechanical properties such as unit weight, absorption ratio, porosity, elastic wave velocity, uniaxial compressive strength, Young's modulus, Poisson's ratio, tensile strength, shore hardness, friction angle and cohesion were investigated for the four different rocks mainly distributed at a studied mine, which were dolomite, felsite, granite and magnetite. The mechanical properties of the four different rocks were compared by means of statistical analyses, whereupon the felsite and the granite turned out to have more strength characteristics than the magnetite. The correlation of mechanical properties was also investigated, whereupon a few results against the general correlation were found out. The failure criteria of the four different rocks were finally discussed by means of both Mohr-Coulomb criterion and Hoek-Brown criterion.

• Geomechanics and Engineering
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• v.31 no.5
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• pp.529-543
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• 2022

The lattice-spring-based synthetic rock mass model (LS-SRM) technique has been extensively employed in large open-pit mining and underground projects in the last decade. Since the LS-SRM requires a complex and time-consuming calibration process, a robust approach was developed using the Response Surface Methodology (RSM) to optimize the calibration procedure. For this purpose, numerical models were designed using the Box-Behnken Design technique, and numerical simulations were performed under uniaxial and triaxial stress states. The model input parameters represented the models' micro-mechanical (lattice) properties and the macro-scale properties, including uniaxial compressive strength (UCS), elastic modulus, cohesion, and friction angle constitute the output parameters of the model. The results from RSM models indicate that the lattice UCS and lattice friction angle are the most influential parameters on the macro-scale UCS of the specimen. Moreover, lattice UCS and elastic modulus mainly control macro-scale cohesion. Lattice friction angle (flat joint fiction angle) and lattice elastic modulus affect the macro-scale friction angle. Model validation was performed using physical laboratory experiment results, ranging from weak to hard rock. The results indicated that the RSM model could be employed to calibrate LS-SRM numerical models without a trial-and-error process.

• The Journal of Engineering Geology
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• v.14 no.1
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• pp.105-121
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• 2004

The purpose of this study is to investigate the relationship between petrographical and engineering properties of granitic rocks, widely used as building and ornamental stones in Korea, at the Namwon are a. This area is one of the most famous area as a domestic dimension stone production. The granitic rocks were examined for grain sizes, modal compositions and then same samples were tested to determine specific gravity, water absorption, porosity, uniaxial compressive strength, tensile strength, abrasive hardness, P-wave velocity, modulus of elasticity and Poisson's ratio. It is suggested that the influence of the grain size on the engineering properties is more important than that of the mode of mineralogical compositions. And quartz contents also significantly influence the engineering properties of granitic rocks.

• Tunnel and Underground Space
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• v.26 no.2
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• pp.110-119
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• 2016

The purpose of this study is to evaluate the applicability of tailing in the ${\bigcirc}{\bigcirc}$ mine as a grout material. For the purpose, XRD analysis was performed for mineralogical properties of tailing. In addition, flow, velocity, and uniaxial compressive strength tests were carried out for physical and mechanical properties of a grout material with the mixing ratio of cement and tailing and curing periods. By the result of XRD analysis, tailing of the mine was found to mostly consist of quartz, galena, and pyrite. The flow observed by the flow test showed decreasing tendency with increasing the mixing ratio of tailing. The velocity was also lowered with increasing the mixing ratio of tailing regardless of curing periods. The uniaxial compressive strength as well as Young's modulus also show a tendency to decrease with increasing the mixing ratio of tailing independently on the curing periods. Considering only the physical and mechanical properties of a grout material with tailing, the results are considered to be sufficiently used as a grout material. However, since metallic minerals such as galena and pyrite in tailing contents and these are causing environmental contamination, countermeasures should be considered for this problem in future.

• Tunnel and Underground Space
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• v.33 no.3
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• pp.109-125
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• 2023

Disposal repository for high-level radioactive waste secures its safety by means of engineered and natural barriers. The performance of these barriers should be tested and verified through various aspects in terms of short and/or long-term. KAERI has been conducting various in-situ demonstrations in KURT (KAERI Underground Research Tunnel). After completing previous experiment, a conceptual design of an improved in-situ experiment, i.e. K-COIN (KURT experiment of THMC COupled and INteraction), was established and detailed planning for the experiment is underway. Preliminary characterizations were conducted in KURT for siting a K-COIN test site. 15 boreholes with a depth of about 20 m were drilled in three research galleries in KURT and intact rock specimens were prepared for laboratory tests. Using the specimens, physical measurements, uniaxial compression, indirect tension, and triaxial compression tests were conducted. As a result, specific gravity, porosity, elastic wave velocities, uniaxial compressive strength, Young's modulus, Poisson's ratio, Brazilian tensile strength, cohesion, and internal friction angle were estimated. Statistical analyses revealed that there did not exist meaningful differences in intact rock properties according to the drilled sites and the depth. Judging from the uniaxial compressive strength, which is one of the most important properties, all the specimens were classified as very strong rock so that mechanical safety was secured in all the regions.

• Journal of the Korean Society of Industry Convergence
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• v.8 no.2
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• pp.77-84
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• 2005

Foliated metamorphic, stratified sedimentary and regularity jointed rocks have properties(physical, mechanical) that vary with direction (${\beta}^{\circ}$) and are said to be anisotropic. The ground in Daegu area consists of shales, clastic sedimentary rocks. These shales have plane anisotropic or transversely isotropy characteristics. Engineering characteristics of shale in Daegu area are investigated by performing a series of rock test to the bedding(${\beta}$ =0, 30, 60, and 90 degrees). The results of tests show that the uniaxial compressive strength is a maximum at ${\beta}$ = 0, $90^{\circ}$ and is a minimum when ${\beta}$ is around 60 degree.

• Geomechanics and Engineering
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• v.34 no.6
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• pp.697-726
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• 2023

Brittleness as an important property of rock plays a crucial role both in the failure process of intact rock and rock mass response to excavation in engineering geological and geotechnical projects. Generally, rock brittleness indices are calculated from the mechanical properties of rocks such as uniaxial compressive strength, tensile strength and modulus of elasticity. These properties are generally determined from complicated, expensive and time-consuming tests in laboratory. For this reason, in the present research, an attempt has been made to predict the rock brittleness indices from simple, inexpensive, and quick laboratory test results namely dry unit weight, porosity, slake-durability index, P-wave velocity, Schmidt rebound hardness, and point load strength index using multiple linear regression, exponential regression, support vector machine (SVM) with various kernels, generating fuzzy inference system, and regression tree ensemble (RTE) with boosting framework. So, this could be considered as an innovation for the present research. For this purpose, the number of 39 rock samples including five igneous, twenty-six sedimentary, and eight metamorphic were collected from different regions of Iran. Mineralogical, physical and mechanical properties as well as five well known rock brittleness indices (i.e., B₁, B₂, B₃, B₄, and B₅) were measured for the selected rock samples before application of the above-mentioned machine learning techniques. The performance of the developed models was evaluated based on several statistical metrics such as mean square error, relative absolute error, root relative absolute error, determination coefficients, variance account for, mean absolute percentage error and standard deviation of the error. The comparison of the obtained results revealed that among the studied methods, SVM is the most suitable one for predicting B₁, B₂ and B₅, while RTE predicts B₃ and B₄ better than other methods.