• The Journal of Engineering Geology
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• v.34 no.1
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• pp.137-146
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• 2024

The pertinent Korean Industrial Standard (KS F) requires that rocks dried at 105 ± 5℃ be taken out of the oven into air and weighed on a scale. However, when rocks are exposed to air after the drying process, they absorb moisture, meaning that their weight will increase. In this study, eight cubic samples of Hwangdeung granite of different sizes were used to measure and compare the dry weight. The dry singularity weight measured in air was smaller than that measured in the drying oven. The difference in dry weight showed a positive correlation with sample size. Conversely, the difference in dry weight per unit weight of rock showed a negative correlation with sample size. The weight of a rock sample exposed to air is determined by the magnitude of the influence of convection currents occurring around the heated rock and the influence of moisture absorption in air. A singularity occurs when the magnitudes of these two effects are equal. The larger the rock sample, the longer the time taken for the singularity to occur, the greater the weight loss of the sample, and the longer the time taken for the sample to return to the initially measured weight on account of the greater moisture absorption for larger samples than smaller samples. In the future, research into the singularity and dry weights measured inside the drying oven will help to identify and address the limitations of the current KS F testing regulations.

• Korean Journal of Remote Sensing
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• v.23 no.6
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• pp.493-500
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• 2007

In general, it accomplished a spectral reflectance analysis to be, the measurement results appear differently by targets, methods and condition. This paper presents a standard methodology for preprocessing mineral/rock samples and setting the distance from a target to the sensor, and then examines closely the spectral features for pyrophyllite. The size of mineral/rock samples is various according to the condition and scale of outcrop, so it is important to maintain the distance between the sensor and the sample. Before standardization for preprocessing samples and the sensor and sample distance, we prepare various rock samples (Quartz Porphyry) such as natural rock, pebble, powder and cutting rock. For a qualitative analysis to minimize the effect of surface condition of the sample and shadow, we maintains the distance from the sample to the sensor at 30cm and measures three times repeatedly for cutting the sample at $1{\sim}2cm$ thickness. To illustrate the proposed methodology, a case study for pyrophyllite was carried out. In this study, pyrophyllite showed an absorption pattern at wave length of 1.406nm, 1,868nm, 2.180nm and 2.309nm, and a higher grade represented strong absorption at 1.406nm and 2.180 nm. These absorption feature corresponds the band 7 of LANDSAT TM and band 8 of ASTER imageries. So, using these results, pyrophyllite deposits were extracted from other features (such as barren area, concrete area, bed of river, stone pit area etc.).

• Proceedings of the Korean Geotechical Society Conference
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• 2008.03a
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• pp.863-874
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• 2008

We have to judge engineering properties of rock accurately in order to design and construct rock structure safely and economically. Among the rock tests, the test result of UCS(Uniaxial Compressive Strength) is very important factor used in the variety ways for designing and construction of underground structures, rock slope and foundation analysis. But the UCS test has some disadvantages of intact sample preparation such as because the shape of sample has to be regular cylindrical, cube or rectangular. In order to solve those problem, indirect tests are used such as point load test, schmidt hammer test, absorption test, dry density to predict UCS of rock. Those tests are easy to prepare sample and convenient to carry out the tests, so it is simple and costs less. Schmidt hammer test are frequently used in the construction site, because it is handy and easy to use, but there is concern of misuse without classifying the specification of each schmidt hammer. Thus, this study suggested presumptive numerical formula related on each specification of schmidt hammer test, point load test, absorption test and dry density also. We compared presumptive numerical formula and R-square through schmidt rebound assessment method already brought up. Also, through the test we offer the extent of weathering index according to the weathering grade.

• Economic and Environmental Geology
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• v.24 no.1
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• pp.71-79
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• 1991

Anisotropy of magnetic susceptibility (AMS), directional variation of susceptibility in a sample, indicates the relative magnitude and orientation of preferentially aligned magnetic grains in a rock sample and represents important aspects of rock fabrics. This observation leads to various studies which applied the AMS technique to numerous geological problems, especially sedimentology, petrology, structural geology, and tectonics. Since AMS is, relative to conventional methods of petrofabric measurement, quickly measured, easily interpretated, and providing quantitative data, AMS technique has evolved into a powerful tool for detection of rock fabrics and continues to draw the interest of non-specialists as well as magnetists. This paper represents the theory, techniques, and parameters of the relatively new AMS method for estimating petrofabrics and their various applications.

• 지반과기술
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• v.3 no.3
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• pp.15-22
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• 2006

The optimum blasting pattern to excavate a quarry efficiently and economically can be determined based on the minimum production cost, which is generally estimated according to rock fragmentation. Therefore, it is a critical problem to predict fragment size distribution of blasted rocks over an entire quarry. By comparing various prediction models, it can be ascertained that the result obtained from Kuz-Ram model relatively coincides with that of field measurements. Kuz-Ram model uses the concept of rock factor to signify conditions of rock mass such as block size, rock jointing, strength and others. For the evaluation of total production cost, it is imperative to estimate 3-D spatial distribution of rock factor for the entire quarry. In this study, a sequential indicator simulation technique is adopted for estimation of spatial distribution of rock factor due to its higher reproducibility of spatial variability and distribution models than Kriging methods. Further, this can reduce the uncertainty of predictor using distribution information of sample data. The entire quarry is classified into three types of rock mass and optimum blasting pattern is proposed for each type based on 3-D spatial distribution of rock factor. In addition, plane maps of rock factor distribution for each ground level are provided to estimate production costs for each process and to make a plan for an optimum blasting pattern.

• Tunnel and Underground Space
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• v.6 no.1
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• pp.19-29
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• 1996

Back analysis model, capable of calculating the mechanical properties and the in-situ stresses of jointed rock mass, was developed based on the inverse method using a continuum theory. Constitutive equation for the behavior of jointed rock contains two unknown parameters, elastic modulus of intact rock and stiffness of joint, hence algorithm which determines both parameters simultaneously cannot be established. To avoid algebraic difficulties elastic modulus of intact rock was assumed to be known, since the representative value of which would be quite easily determined. Then, the ratio ($\beta$) of joint stiffness to elastic modulus of intact rock was assigned and back analysis for the behavior of jointed rock was carried-out. The value $\beta$ was repeatedly modified until the elastic modulus from back analysis became very comparable to the predetermined value. The joint stiffness could be calculated by multipling the ratio $\beta$ to the final result of elastic modulus. Accuracy and reliability of back analysis procedure was successfully testified using a sample model simulating the underground opening in the jointed rock mass. Applicability of back analysis model for the underground excavation in practice was also verified by analyzing the mechanical properties of jointed rock in which underground oil storage cavern were under construction.

• Journal of the Korean Geotechnical Society
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• v.15 no.3
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• pp.177-197
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• 1999

The measurement of sonic velocities is commonly used as an index of engineering properties of rock, but it is not widely appreciated that this velocity can change markedly with the degree of saturation of the sample. This paper records the nature of this variation as seen in samples of Korean granite. The ISRM method of testing suggested for this index can also create difficulties, especially if vaseline is used as a coupling agent, and invades the samples, and if the sample volume changes with degree of saturation. Careful measurements of the natural variation in sonic velocity that occur in a sample whose saturation is gradually increased may be a means of assessing the relic stresses within it.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.09a
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• pp.743-748
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• 2010

The stability forecasting of rock slope is more difficult than soil slope because catching the sign of failure in monitoring is not easy and deformation of the rock is small in failure process. But in the rock slope, there is small deformation like crack propagation in rock itself and it accumulates gradually in failure process. If it is possible to detect the small change in the rock slope, we can know the failure time exactly. Because the individual signal is gathered in the acoustic emission monitoring, it is possible to monitoring the slope if many sound signal is accumulated. Detection test of acoustic emission was performed. Uniaxial, two types of bending test, and two plane shear test were done with various cement paste sample. Wave propagation velocity of uniaxial test sample was increased with curing time. Wave Analysis give us the result that there is a AE sign signal before the failure, the AE count is suddenly increased. And frequency level 125kHz before failure is changed to level 200-250kHz after failure. In two plane shear test we can catch the AE signal and can know the failure type from wave shape. Monitoring test site is tunnel slope in Hongcheon but special signal is not collected.

• The Journal of Engineering Geology
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• v.18 no.2
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• pp.215-225
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• 2008

In order to investigate the influence factors to compressive and tensile strength of basalt in Cheju Island, rock samples of Pyosenri basalt, trachy-basalt and scoria were taken from Seoguipo-Si Seongsan-Eup area, and a series of uniaxial compressive strength test and Brazilian test were carried out. Especially, these tests were performed in consideration of the loading speed, the moisture content in rock sample, and the anisotropy of rock strength. The uniaxial compressive strength was increased gradually as the loading speed rose. The increasing quantity of uniaxial compressive strength had a difference in each rock types. Also, the strength was decreased with increasing the moisture contents in rock sample by pore water. As the result of test considering the anisotropy of rock strength, the compressive strength in condition of failure occurred parallel to stratified layer is decreased about 12-26% more than that in condition of failure occurred inclined to stratified layer.

• Tunnel and Underground Space
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• v.30 no.4
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• pp.394-403
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• 2020

This technical note describes the calculation method of continuous constant linear velocity Archimedean spiral paths which are applied to the pin-on-disk abrasion test. Approximate constant linear velocity Archimedean spirals have unstable velocities in the very near region of the rotational origin. Thus, in this technical note, the offset distance from the rotational origin was given by using a hollow type rock sample to maintain the constant velocity during the test. Also, to connect the inward and outward spirals continuously, the information of start and end points were input on the next spiral path consecutively. Furthermore, the calculation program was developed to provide convenience for calculating constant linear velocity spirals according to the specimen dimension and abrasion test conditions.