• The Journal of Engineering Geology
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• v.20 no.2
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• pp.213-220
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• 2010

The permeability characterization on the natural barrier for deep geological disposal of radioactive waste is very critical to evaluate total safety and performance assessment of disposal site. However, the confidence level in using previous hydraulic testing equipments consist of simple components to estimate rock mass permeability is not high enough to reflect in situ condition. The purpose of this research is to establish an advanced hydraulic testing equipment, which is applicable to deep borehole (up to 1,000 m), through the improvement of technical problems of previous packer systems. Especially, the straddle packer hydraulic testing equipment was designed to adopt both the hydraulic downhole shut-in valve(H-DHSIV) to minimize the wellbore storage effect and the real time data acquisition system to measure the pressure changes of test interval including its upper and lower parts. The results from this research lead to not only improve current technical level in the field of hydraulic testing but also provide important information to radioactive waste disposal technology development and site characterization project.

• Journal of the Korean Institute of Telematics and Electronics C
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• v.36C no.1
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• pp.59-65
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• 1999

In this paper, we design a entorpy encoder of HDTV/DTV encoder blocks on the basis of MPEG-II. The designed entropy encoder outputs its bit stream at 9Mbps bit rate inserting zero-stepping block to protect the depletion of buffer in case that the generated bit stream is stored in buffer and uses not only PROM bit combinational circuit to solve the problem of critical path, and packer block, one of submerge, is designed to packing into 24 bit unit using barrel shifter, and it is constructed to blocks of header information encoder, input information delay, submerge, and buffer control. Designed circuits is verified by VHDL function simulation, as a result of performing P&R with Gate compiler that apply $0.8{\mu}m$ Gate Array specification, pin and gate number of total circuits has been tested to each 235 and about 120,000.

• The Journal of Engineering Geology
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• v.10 no.1
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• pp.13-25
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• 2000

A three-dimensional discrete fracture network model based on probabilistic characteristics of fracture geometry and transmissivity was designed to calculate the conductivity tensor and to estimate theanisotropy of conductivity. The conductivities, $K_p$, obtained from the numerical simulation of single-holepacker test corresponded well to those from the field tests. From this, it can be concluded that thefracture network model designed in this study can represent hydraulic characteristics of in-situ fractured rock mass. Block-scale conductivities, $K_b$, estimated from the modelling of steady-state flow through the REV-scale block were ranged between the arithmetic mean and harmonic mean of theconductivity estimates from packer tests. The conductivity along north-south direction was 1.4 timesgreater than that along the east-west direction. It was concluded that the anisotropy of conductivitywas insignificant. It was also found that there was a little correlation between $K_b$ and $K_p$. This would be to that the conductivities from the packer test simulation was strongly dependent on thetransmissivity and the number of fractures within the packer test intervals.

• The Journal of Engineering Geology
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• v.12 no.3
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• pp.319-332
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• 2002

This study is focused on the characterization of an effective hydraulic conductivity in each hydrogeologic unit assumed as an equivalent continuum medium in the granitic area. Four boreholes of 3" diameter were installed and a Multi-packer system was facilitated in the selected borehole. Various in-situ tests including the fracture logging, constant injection and fall-off tests, slug and pulse tests were carried out. A hydrogeologic unit was defined into the upper and lower zones based on the variation of fracture properties and hydraulic conductivities. The difference of the result obtained by the various hydraulic tests and the effective characterization techniques on rock mass permeability are also discussed. The effective hydraulic conductivity of the upper unit was measured by two times(5.27E-10 m/s~7.57E-10 m/s) that of the lower unit(2.45E-10 m/s~6.81E-10 m/s)through the constant injection and fall-off tests.

• Tunnel and Underground Space
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• v.27 no.5
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• pp.263-270
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• 2017

Hydraulic rock splitting is a technique which leads to failure of rockmass by means of water injection with a pressure higher than the tensile strength of rockmass, using straddle packer installed in boreholes drilled from free surface. Field tests were conducted in this study for several slopes of biotite granite according to various designs for borehole layout and water injection. Test results showed that new cracks were generated to connect to adjacent holes or that pre-existed cracks were propagated by injection, finally leading to failure. In particular, this study suggests the possibility of controlling the direction of generated cracks with guide slot, since new cracks were generated parallel to the guide slots carved on a borehole wall before injection. Various types of borehole layout and injection methods should be further developed for the practical uses, considering the factors influencing on crack generation.

• The Journal of Engineering Geology
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• v.9 no.3
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• pp.227-241
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• 1999

Groundwater flow in a fractured rock mass is related to the geometric characteristics of the fracture system. The objective of this study aims to analyze the probabilistic density function of fracture properties md their relations to the hydraulic conductivity in volcanic rocks of the northern Yosu area. Fracture characteristics were investigated by core logging and acoustic televiewer logging in four boreholes and the hydraulic conductivity was obtained from the constant pressure injection and fall-off tests. The 303 fractures were grouped into three sets by their orientation and three fracture types by the degree of opening in aperture. As a result of the study, the hydraulic conductivity in the test section intersected by open and semi-open fractures, conductive fractures, and set 1 fractures was very high, while closed fractures did rarely affect the hydraulic conductivity. It was recognized that the hydraulic conductivity in a fractured rock mass was preferentially affected by the aperture size of conductive fractures and fracture intersection frequency and size, secondly.

• Journal of Soil and Groundwater Environment
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• v.24 no.1
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• pp.35-42
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• 2019

In installation of groundwater wells, grouting materials are injected between the groundwater borehole and the inner casing in order to prevent infiltration of contaminated groundwater from the top soil layers into wells. The injection device of grouting materials is commonly composed of an inlet head device with an expansion packer, a cylinder capable of storing the grouting materials, and an air cylinder. In this work, two types of common grouting materials, silicon and cement materials, were tested for their performances as grouting media. For silicon. silicon was mixed with clay or calcite, and tested for their tensile strength and underwater reactivity. Both silicon-clay and silicon-calcite mixtures had adequate flow and adhesiveness. For cement material, general cement, ultra-rapid harding cement, and natural cement were respectively mixed with three different soil types including coarse-grained granite, fine-grained granite, and gneiss, and direct shearing tests were conducted after hardening. Under grouting depth condition of 30 m, the minimum adhesive strength was greater for weathered gneiss than non-weathered gneiss with its maximum values obtained from the mixtures of ultra rapid-harding cement.

• The Journal of Engineering Geology
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• v.23 no.2
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• pp.171-186
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• 2013

A drilling project was undertaken to characterize the geochemical relationship and the occurrence of radioactive materials at a test site among public-use groundwaters previously known to have high occurrence of uranium and radon-222 in the Daejeon area. A borehole (121 m deep) was drilled and core rocks mainly consist of two-mica granite, and associated with pegmatite and dykes of intermediate composition. The groundwater samples collected at six different depths in the borehole by a double-packed system showed the pH values ranging from neutral to alkaline (7.10-9.3), and electrical conductivity ranging from 263 to 443 ${\mu}S/cm$. The chemical composition of the borehole groundwaters was of the $Ca-HCO_3(SO_4+Cl)$ type. The uranium and Rn-222 contents in the groundwater were 109-1,020 ppb and 9,190-32,800 pCi/L, respectively. These levels exceed the regulation guidelines of US EPA. The zone of the highest groundwater uranium content occurred at depths of 45 to 55m. The groundwater chemistry in this zone (alkaline, oxidated, and high in bicarbonate) is favorable for the dissolution of uranium into groundwater. The dominant uranium complex in groundwater is likely to be $(UO_2CO_3)^0$ or $(UO_2HCO_3)^+$. Radon-222 content in groundwater shows an increasing trend with depth. The uranium and thorium contents in the core were 0.372-47.42 ppm and 0.388-11.22 ppm, respectively. These levels are higher values than those previously been reported in Korea. Microscopic observations and electron microprobe analysis(EPMA) revealed that the minerals containing U and Th are monazite, apatite, epidote, and feldspar. U and Th in these minerals are likely to substitute for major elements in crystal lattice.

• The Journal of Engineering Geology
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• v.22 no.1
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• pp.95-111
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• 2012

This study investigated the relationship between the geochemical environment and the occurrence of natural radioactive materials (uranium and Rn-222) in borehole groundwater at an Icheon site. The drill core recovered from the study site consists mainly of biotite granite with basic dykes. The groundwater samples were collected at four different depths in the borehole using the double-packed system. The pH range of the groundwater was 6.5~8.6, and the chemical type was Ca-$HCO_3$. The ranges of uranium and Rn-222 concentrations in the groundwater were 8.81~1,101 ppb and 5,990~11,970 pCi/L, respectively, and concentrations varied greatly with depth and collection time. The ranges of uranium and thorium contents in drill core were 0.53~18.3 ppm and 6.66~17.5 ppm, respectively. Microscope observations and electron microprobe analyses revealed the presence of U and Th as substituted elements for major composition of monazite, ilmenite, and apatite within K-feldspar and biotite. Although the concentration of uranium and thorium in the drill core was not high, the groundwater contained a high level of natural radioactive materials. This finding indicates that physical factors, such as the degree of fracturing of an aquifer and the groundwater flow rate, have a greater influence on the dissolution of radioactive materials than does the geochemical condition of the groundwater and rock. The origin of Rn-222 can be determined indirectly, using an interrelationship diagram of noble gas isotopes ($^3He/^4He$ and $^4He/^{20}Ne$).

• The Journal of Engineering Geology
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• v.15 no.2 s.42
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• pp.213-227
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• 2005

This study aims to assess the problems with investigation method and to suggest the complementary solutions by comparing the predicted data from surface investigation with the outcome data from underground cavern. In the study area, one(NE-1) of 6 fracture zones predicted during the surface investigation was only confirmed in underground caverns. Therefore, it is necessary to improve the confidence level for prediction. In this study, the fracture classification criteria was quantitatively suggested on the basis of the BHTV images of NE-1 fracture zone. The major orientation of background fractures in rock mass was changed at the depth of the storage cavern, the length and intensity were decreased. These characteristics result in the deviation of predieted predicted fracture properties and generate the investigation bias depending on the bore hole directions and investigated scales. The evaluation of hydraulic connectivity in the surface investigation stage needs to be analyze by the groundwater pressures and hydrochemical properties from the monitoring bore hole(s) equipped with a double completion or multi-packer system during the test bore hole is pumping or injecting. The hydraulic conductivities in geometric mean measured in the underground caverns are 2-3 times lower than those from the surface and furthermore the horizontal hydraulic conductivity in geometric mean is six times lower than the vertical one. To improve confidence level of the hydraulic conductivity, the orientation of test hole should be considered during the analysis of the hydraulic conductivity and the methodology of hydro-testing and interpretation should be based on the characteristics of rock mass and investigation purposes.