• Tunnel and Underground Space
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• v.19 no.6
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• pp.473-478
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• 2009

The accuracy of point load apparatus is depend on point to point coaxial fitting. Also, the estimation of applied point load using the pressure gauge frequently lead to erroneous results. An improved point load apparatus has been developed in this study by mounting linear bearing on polished support rod, and eccentric error of point to point axis has been sustained less than 0.1 mm even under series of extreme work load conditions. Two digital displacement gauges are attached to measure the distance from point to point with sample specimen. A load cell mounted at the end of upper conical platen measure the applied net load on sample instead of preassure gauge. Total of 107 point load tests has been achieved to assure the quality and performance of developed apparatus. This exercise turned out to be successful.

• Journal of the Korean GEO-environmental Society
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• v.13 no.11
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• pp.27-35
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• 2012

The discontinuity of rock is one of important elements that have impact on the dynamic movement of rock. A slope made of gneiss has complicated geological structure because of the gneiss forming process through metamorphism covering wide range and the anisotropic structure with foliation. In this study, before cutting slope, the rock of slope had been found as a good quality by the boring test. But during construction tension cracks had occurred in the section with 170m length during large-scale excavation work with depth more than 20m. Ground surface geological investigation, boring exploration, resistivity logging and borehole image processing had been done to find the causes of the tension crack. It was possible to estimate the scale of fault existing in large area through resistivity logging and geological investigation. Large scale slickenside and fault clay had been found as the result of comprehensive analysis.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.09a
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• pp.519-526
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• 2010

The construction site for $\bigcirc\bigcirc$ transformer substation was located at a mountain valley. In order to prepare the site, the valley was first filled with crushed rock debris up to 63m. Since the main concern of this project is to minimize differential settlement of the foundation of transformer facilities, dynamic compaction was performed every 7m followed by reinforcement with EMP(Ez-Mud Piling). The EMP is one of bored piling methods, in which a hole is bored by means of air percussion and maintain by injecting Ez-Mud. Then a PHC pile (Pretensioned spun High strength Concrete pile) is embedded and finalized with a hammer. In this study, bearing capacities and long term behavior of a pile installed by EMP were investigated. To achieve these objectives, a series of tests such as static and dynamic load tests were conducted. In addition, a construction quality control standard was proposed based on the test results.

• Tunnel and Underground Space
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• v.23 no.1
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• pp.78-85
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• 2013

A primary objective in creating a stratified thermal storage is to maintain the thermodynamic quality of energy, so thermally stratified energy can be extracted at temperatures required for target activities. The separation of the thermal energy in heat stores to layers with different temperatures, i.e., the thermal stratification is a key factor in achieving this objective. This paper introduces different methods that have been proposed to characterize the thermal stratification in heat stores. Specifically, this paper focuses on the methods that can be used to determine the ability of heat stores to promote and maintain stratification during the process of charging, storing and discharging. In addition, based on methods using thermal stratification indices, the degrees of stratification of stored energy in Lyckebo rock cavern in Sweden were compared and the applicability of the methods was investigated.

• Journal of the Korean Society of Earth Science Education
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• v.2 no.1
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• pp.80-90
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• 2009

The purpose of this study is to investigate the characteristics of the mind maps which were drawn with pencil or color pens by elementary students. For this study, 31 students of the 6th grade were selected and trained mind mapping. After training, the subjects had drawn mind maps with color pens about the ROCK for 15minutes and drew mind maps with pencil after 2days of mind mapping using color pens. In addition to activities of mind mapping, the students handed in their papers which were written one's impression of drawing two kinds of mind mapping. The results were follows: First, in central circle which was linked words connected firstly with ROCK as key word, the difference of 2kinds mind maps were little showed in the quantity and quality of the words, branches and their adequacy. Second, the mind maps using pencils had more words, branches and images than mind maps of using color pens in the whole assessment. Third, the most students suggested that the mind mapping using pencil were advantage to economy of time, retouching words and branches, also the mind mapping using pencil made the students relax the strain for drawing it because of retouching possibility. Consequently, the results of this study suggest the mind mapping using pencil has advantage effect on the purpose of gaining students' thinking abundantly and economy of time in elementary science classes.

• Tunnel and Underground Space
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• v.18 no.2
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• pp.134-148
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• 2008

The state of in situ stress is an important factor in considering the suitability of a site as a geological repository for nuclear waste. In this study, three-dimensional distinct numerical analysis was conducted to investigate the effect of deformation zones on the state of stress in the Oskarshamn area, which is one of two candidate sites in Sweden. A discontinuum numerical model was constructed by explicitly representing the numerous deformation zones identified from site investigation and far-field tectonic stress was applied in the constructed model. The numerical model successfully captured the variation of measured stress often observed in the rock mass containing large-scale fractures, which shows that numerical analysis can be an effective tool in improving the understanding of the state of stresses. Discrepancies between measured and modelled stress are attributed to the inconsistent quality of measured stress, uncertainty in geological geometry. and input data for fractures.

• Geophysics and Geophysical Exploration
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• v.8 no.1
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• pp.112-117
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• 2005

Geophysical logging is routinely undertaken as part of most coal mine exploration programs. Currently, the main application for the logs is to determine coal seam depth and to qualitatively estimate coal quality, lithology, and rock strength. However, further information can be obtained, if quantitative log interpretation is made. To assist in the uptake of quantitative interpretation, we discuss log responses in terms of the mineralogy of the clastic sedimentary rocks frequently found in the Australian black coal mining areas of the Sydney and Bowen Basins. We find that the log responses can be tied to the mineralogy with reasonable confidence. Ambiguities in the interpretation will be better resolved if a full suite of logs is run. A method for checking for internal consistency, by comparing calculated and observed velocities, is also described. A key driver for quantitative interpretation is geotechnical characterisation. We propose a classification system for clastic rocks that takes into consideration physical rock properties that can be inferred from geophysical logs.

• New & Renewable Energy
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• v.17 no.3
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• pp.32-41
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• 2021

A groundwater source heat pump (GWHP) was developed in this study by adapting a borehole heat exchanger with closed-loop and open-loop systems in a new building. In the pilot test building, the air-conditioning on the second floor was designed to employ a closed-loop system and that on the third floor had an open-loop system. The GWHP design is based on the feasibility of groundwater resources at the installation site. For the hydrogeological survey of the study site, pumping and injection tests were conducted, and the feasibility of GWHP installation was evaluated based on the air-conditioning load demand of the building. The site was found to be satisfactory for the design capacity of the thermal load and water quality. In addition, the effect of groundwater movement on the performance of the closed-loop system was tested under three different operational scenarios of groundwater pumping. The performance of the system was sustainable with groundwater flow but declined without appropriate groundwater flow. From long-term observations of the operation, the aquifer temperature change was less than 2℃ at the observation well and 5℃ at the injection well with respect to the initial groundwater temperature. This pilot study is expected to be of guidance for developing GWHPs at fractured rock aquifers.

• Journal of the Korean GEO-environmental Society
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• v.9 no.7
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• pp.25-35
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• 2008

In domestic cases, the standard support pattern of 2-lanes road tunnels is presented because construction experience and high degree various data was abundant. But, it is not desirable to apply standard for 2-Arch tunnels that the precedent and measuring data is insufficient existing support pattern blasting plan and interpretation of separate way concerning specific terrain and rock quality. In this study, behavior according to load distribution ratio and Unsymmetrical Pressure about standard support pattern which is applied in design and construction of 2-arch tunnels was analysed and the examination of blasting vibration has influence on the center wall is conducted as a consequence reasonableness of support whether or not with presumed support pressure and ground reaction curve method. In result appropriateness of standard support pattern, support quantity is proper but considers specific terrain and rock quality condition when design and construction of further step 2-arch tunnel standard support pattern must be decided by considering terrains, soil properties and construction condition of the objective tunnel.

• Tunnel and Underground Space
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• v.16 no.5 s.64
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• pp.405-412
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• 2006

It is well known that shotcrete is the most important support member for the construction of large underground spaces. Generally, the strength of the field shotcrete is heavily dependent on the field mixing and spraying conditions so that it is different from the strength of the shotcrete mixed in laboratories. As a support member, the early strength of shotcrete unlike concrete is very important to the initial stabilization of the underground spaces. Therefore, the field methods to efficiently test the early strength of shotcrete have been highly required. This paper aimed to verify the pneumatic pin penetration test and the point load test for measuring the early strength of the field shotcrete. As a result of the experiments through a series of uniaxial compression, pin penetration, and point load tests for the range of the early shotcrete strength, two equations to estimate reliably the uniaxial compressive strength by the pin penetration and the point load tests were acquired.