• Analytical Science and Technology
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• v.18 no.3
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• pp.216-223
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• 2005

In this study, several kinds of volatile amines in ambiant air were collected and their concentrations were expected from the calibration curves prepared by standard solutions of 7 amines by the official measuring method prescribed in Japanese Offensive Odor Law. The obtained calibration curves showed a good linearity and the detection limit of trimethyl amine was found to be about 0.033 ppb (0.040 ng) in case of 50 liters air. It means that trimethyl amine could be detected with the concentration of lower than its permitting level at the border line of companies. As typical examples of measuring amines in air, results of investigation of two sewage works and one rendering plant around the capital area indicated that 4 kinds of amines, i.e. methyl amine, dimethyl amine, trimethyl amine and isopropyl amine were detectable and concentrations of trimethyl amine at the primary sedimentation pond and sludge dewatering building of the sewage plant A showed 9.07 ppb and 7.79 ppb respectively, being over the concentration of odor strength 2.5, And the aeration tank, excrement input facility and indoor of maintenance room of excrement process building in the sewage plant B showed 70.0 ppb of dimethyl amine and 2.44 ppb of trimethyl amine.

• Ecology and Resilient Infrastructure
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• v.6 no.4
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• pp.208-216
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• 2019

This study investigated design factors and removal efficiencies of a sheet flow channel as natural type water improvement techniques in the stream. The channel was designed considering the design factors, then constructed and monitored in the test bed of the Osan stream's floodplain. Water lever, velocity, discharge, T-P, T-N, and NO₃-N were monitored and the removal efficiencies and design formula were suggested. Overall efficiencies of T-P, T-N, and NO₃-N range 10 - 20%, and they show consistent relations with residence times. Minimum velocity requirement is also suggested from the relation of algae conditions and velocities. Relation formula of residence time and removal efficiency will be applicable in the design and operation process of a sheet flow channel.

• Journal of the Korean Geotechnical Society
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• v.28 no.12
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• pp.111-122
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• 2012

Resistivity seismic dilatometer (RSDMT) system is introduced. The resistivity module for obtaining resistivity-depth plot and seismic module for obtaining wave velocity-depth plot are attached to the conventional flat dilatometer testing equipment. To enhance the reliability and repeatability of seismic part in RSDMT, automatic testing system including automatic surface source, PC based data acquisition system and operating program was constructed. To obtain real resistivity value of soil, geometric factor for the array of electrodes in RSDMT was derived empirically. The verification studies for the developed RSDMT system were performed with SPT, CPTu, bender element test and DC resistivity survey. Through one penetration of RSDMT, various soil parameters were obtained and the reliability and repeatability of developed RSDMT system could be checked.

• Tunnel and Underground Space
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• v.30 no.6
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• pp.519-539
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• 2020

We reviewed numerical approaches to assess a hydraulic properties of excavation-disturbed zone (EDZ)created in argillaceous sedimentary rocks. It has been reported that fractures in the sedimentary rocks containing expansive clays are gradually closing due to swelling and their permeabilities are evolving to the level of in-tact rock, which is known as a self-healing or self-sealing process. The numerical approaches introduced here are capable of simulating spatio-temporal variation of EDZ permeability during long-term operation of a repository by including the self-healing characteristics of fractures, which wa observed in laboratory as well as in-situ experiments, The applicability of the numerical approaches was verified from the comparison to in-situ measurements of EDZ permeability at underground research laboratories.

• Journal of the Korean Geotechnical Society
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• v.37 no.7
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• pp.25-34
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• 2021

Since the dredging reclaimed land consisting of soft ground is very weak in support, the difficult and complex factors should be considered in the design to calculate accurate bearing capacity of soft ground. Recently, various reinforcement construction methods of soft ground have been designed for dredged landfills, but the stabilities are predicted by calculating conventional Meyerhof (1974) equation for trafficability in soft ground. Conventional equations increase economic costs by underestimating bearing capacity of weak ground in order to ensure constructive safety, so a modified equation has been proposed from the literature. The paper attempts to experiment and compute important factors, such as stitching fiber and seam tensile strength of geotextiles, that are not theoretically considered and can be identified in the field. In addition, The evaluation of the bearing capacity of the modified equation is verified to be stable for trafficability through the plate bearing test performed on site.

• Journal of the Korean Geotechnical Society
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• v.22 no.3
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• pp.23-35
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• 2006

Equivalent linear analysis is widely used in estimating local seismic site effects. The soil behavior in the analysis is often assumed to be rate-independent and is not influenced by the seismic loading frequency. Laboratory results, however, indicate that cohesive soil behavior is greatly influenced by the loading frequency. A new equivalent linear analysis method that accounts for the loading frequency dependent soil behavior is developed and used to perform a series of one dimensional site response analyses. Results indicate that while frequency dependent shear modulus has limited influence on computed site response, frequency dependent soil damping greatly filters out high frequency components of the ground motion and thus results in lower response.

• Journal of Korean Tunnelling and Underground Space Association
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• v.12 no.6
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• pp.451-461
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• 2010

Utilization of the fiber reinforced polymer (FRP) material has been enlarged as a substitution material to the general construction materials having certain long-term problems such as corrosion, etc. However, it could be difficult to apply the FRP material, which has a linear shape generally, to an arch-shaped tunnel structure. Therefore, an attempt has been made in this study to develop a device to form a designed cross section of FRP material by pulling out with a curvature. A sample of the circled FRP product was successfully produced and then the sample has been tested to identify its physical characteristics. Then, intensive feasibility studies on the circled FRP panel to be used for a tunnel lining structure have been carried out by numerical analyses. As a result, it appears that the new circled FRP-concrete composite panel has a high capability to be used for a tunnel lining material without any structural problem.

• Journal of the Korean Geosynthetics Society
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• v.20 no.4
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• pp.85-93
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• 2021

The seventy percentage of Korean Peninsular is covered by the mountainous area, and the depth of west sea and south sea is relatively shallow. Therefore, a large scale land reclamation from the sea has been implemented for the construction of industrial complex, residental area, and port and airport facilities. The common problem of reclaimed land is consisted of soft ground, and hence it has low load bearing capacity as well as excessive settlement upon loading on the ground surface. The hollow concrete block has been used to reinforce the loose and soft foundation soil where the medium-high apartment or one-story industrial building is being planned to be built. Recently the earthquakes with the magnitude of 4.0~5.0 have been occurred in the west coastal and southeast coastal areas. Lee (2019) reported the advantages of hollow concrete block reinforced shallow foundation through the static laboratory bearing capacity tests. In this study, the dynamic behavior of hollow concrete block reinforced sandy ground with filling the crushed stone in the hollow space has been investigated by the means of shaking table test with the size of shaking table 1000 mm × 1000 mm. Three types of seismic wave, that is, Ofunato, Hachinohe, Artificial, and two different accelerations (0.154 g, 0.22 g) were applied in the shaking table tests. The horizontal displacement of structure which is situated right above the hollow concrete block reinforced ground was measured by using the LVDT. The relative density of soil ground are varied with 45%, 65%, and 85%, respectively, to investigate the effectiveness of reinforcement by hollow block and measured the magnitude of lateral movement, and compared with the limit value of 0.015h (Building Earthquake Code, 2019). Based on the results of shaking table test for hollow concrete block reinforced sandy ground, honeycell type hollow block gives a large interlocking force due to the filling of crushed stone in the hollow space as well as a great interface friction force by the confining pressure and punching resistance along the inside and outside of hollow concrete block. All these factors are contributed to reduce the great amount of horizontal displacement during the shaking table test. Finally, hollow concrete block reinforced sandy ground for shallow foundation is provided an outstanding reinforced method for medium-high building irrespective of seismic wave and moderate accelerations.

• Journal of Environmental Impact Assessment
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• v.29 no.3
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• pp.157-181
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• 2020

Sediments from rivers, lakes and marine ports serve as end points for pollutants discharged into the water, and at the same time serve as sources of pollutants that are continuously released into the water. Until now, the contaminated sediments have been landfilled or dumped at sea. Landfilling, however, was expensive and dumping at sea was completely banned due to the London Convention. Therefore, this study applied contaminated sedimentation soil of 'Royal Palace Livestock Complex' as soil purification method. Soil remediation methods were applied to pretreatment, composting, soil washing, electrokinetics, and thermal desorption by selecting overseas application cases and domestically applicable application technologies. As a result of surveying the site for pollutant characteristics, Disolved Oxigen (DO), Suspended Solid (SS), Chemical Oxygen Demand (COD), Total Nitrogen (TN), and Total Phosphorus (TP) exceeded the discharged water quality standard, and especially SS, COD, TN, and TP exceeded the standard several tens to several hundred times. Soil showed high concentrations of copper and zinc, which promote the growth of pig feed, and cadmium exceeded 1 standard of Soil Environment Conservation Act. In the pretreatment technology, hydrocyclone was used for particle size separation, and the fine soil was separated by more than 80%. Composting was performed on organic and Total Petroleum Hydrocarbon (TPH) contaminated soils. TPH was treated within the standard of concern, and E. coli was analyzed to be high in organic matter, and the fertilizer specification was satisfied by applying the optimum composting conditions at 70℃, but the organic matter content was lower than the fertilizer specification. As a result of continuous washing test, Cd has 5 levels of residual material in fine soil. Cu and Zn were mostly composed of ion exchange properties (stage 1), carbonates (stage 2), and iron / manganese oxides (stage 3), which facilitate easy separation of contamination. As a result of applying acid dissolution and multi-stage washing step by step, hydrochloric acid, 1.0M, 1: 3, 200rpm, 60min was analyzed as the optimal washing factor. Most of the contaminated sediments were found to satisfy the Soil Environmental Conservation Act's standards. Therefore, as a result of the applicability test of this study, soil with high heavy metal contamination was used as aggregate by applying soil cleaning after pre-treatment. It was possible to verify that it was efficient to use organic and oil-contaminated soil as compost Maturity after exterminating contaminants and E. coli by applying composting.

• Journal of the Korean Society for Nondestructive Testing
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• v.27 no.2
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• pp.105-114
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• 2007

Two-dimensional imaging of $V_s$ profile becomes more important in Korea because of the large horizontal variation of soil stiffness. To obtain a shear-wave velocity profile in geotechnical practice, various seismic nondestructive investigation methods are being frequently used. In this study, harmonic wavelet analysis of wave (HWAW) method is applied to the determination of $V_s$ profile to overcome some of weaknesses in the existing surface wave methods. HWAW method which is based on time-frequency analysis using harmonic wavelet transform has been developed to determine phase and group velocities of waves. Field testing of this method is relatively simple and fast because one experimental setup which consists of one pair of receivers is needed to determine $V_s$ profile of site. The proposed method uses the signal portion of the maximum local signal/noise ratio to evaluate the phase velocity to minimize the effects of noise, and uses single array inversion which considers receiver locations. Field tests were performed in 2 sites in order to evaluate accuracy of test method and estimate the applicability of 2-D imaging by HWAW method. Through field applications and comparison with other test results, the good accuracy and applicability of the proposed method were verified.