• Economic and Environmental Geology
• /
• v.27 no.3
• /
• pp.295-311
• /
• 1994

A comprehensive in-situ tests are performed to define the hydrogeologic and hydrodispersive characteristics such as hydraulic conductivities, longitudinal dispersivity, and average linear velocities as well as conducting flow-net analysis at the study area. The results show that the study area is very heterogeneous so that hydraulic conductivities range from $6.45{\times}10^{-7}$ to $1.15{\times}10^{-5}m/s$ with average linear velocities of 0.34~0.62m/day. Whole groundwater in upper-most aquifer is discharging into the sea with specific discharge rate of $7.2{\times}10^{-3}$ to $1.3{\times}10^{-2}m/day$. The longitudinal dispersivity of the aquifer is estimated about 4.8m through In-situ injection phase test. The area is highly vulnerable to potential contaminant sources due to it's high value of DRASTIC index ranging from 139 to 155 and also under water table condition with very shallow groundwater level. To delineate contaminant plumes of toxic NaOH and carcinogenic benzene when these substances are assumed to be leaked through existing TSDF at the study area by unexpected accidents or spill, Aquifer Simulation Model (ASM) including Flow and Transport Model is used. Te simulated results reveal that the size of NaOH plume after 5 years continuous leak is about $250{\times}100m$ and benzene after 10 years, $490{\times}100m$. When the groundwater is abstracted about 50 days, which is maximum continuously sustained no-precipitation period during 30 years, with pumping rate of $100m^3/day$, THWELL program shows that the groundwater is adversly affected by sea water intrusion.

• 한국지구물리탐사학회:학술대회논문집
• /
• 2003.11a
• /
• pp.142-149
• /
• 2003

Blind hydraulic backfilling is a commonly used technique for subsidence control of the strata over unapproachable waterlogged underground excavations. In this investigation model studies on all the three variants of this technique, namely, hydro-pneumatic or air-assisted gravity backfilling, pumped-slurry backfilling and simple gravity backfilling, have been carried out in fully transparent models of the underground excavations. On examination of the filling process, it was revealed that in all the three cases, the basic process of filling occurs by sand transport along one or more meandering channels. The relative influence of sand, water and air flow rates on the area of filling from a single inlet point and the hydraulic pressure loss per unit length were studied in details. In hydro-pneumatic backfilling process, the air bubbles while moving upward through the meandering channels provide an additional buoyant force over and above the available hydraulic head. In this way the area of filling from a single borehole may be quite large even at small flow rates of water. During actual field implementation the injected air, if not released completely from the rise side holes, may cause troubles by way of creating potholes on the surface. The pumped-slurry technique has shown its capability of filling a relatively larger area at faster rate, especially when high-volume, low-pressure method was selected. But simple gravity filling was also found to be equally effective method as slurry pumping, especially when flow rates were high. In the second and third method discussed above, examination of variations of injection pressure was also done and its relation with physical phenomenon was also attempted. Some empirical relationships were also developed using multivariate regression with a view to help the practicing engineers.

• 한국신재생에너지학회:학술대회논문집
• /
• 2011.05a
• /
• pp.197.1-197.1
• /
• 2011

Target generation capacity of geothermal power generation pilot plant project through the Enhanced Geothermal Systems (EGS) with a doublet system down to 5 km depth was estimated. Production and re-injection temperatures of geothermal fluid were assumed $160^{\circ}C$ and $60^{\circ}C$, respectively, based on reservoir temperature of $180^{\circ}C$ calculated from the geothermal gradient of $33^{\circ}C$ in Pohang area. In this temperature range, 0.11 of thermal efficiency of the binary generation cycle is a practical choice. Assuming flow rates of 40 kg/sec, which is possible in current EGS technology, gross power generation capacity is estimated to reach 1.848 MW. Net generation considering auxiliary power including pumping power for geothermal fluid and condensing (cooling) energy of working fluid can be 1.5 MW.

• Journal of Soil and Groundwater Environment
• /
• v.10 no.4
• /
• pp.33-44
• /
• 2005

On the basis of a stepwise and careful integration of various field and laboratory methods the analysis of groundwater flow characterization was performed with five boreholes (BH-1, -2, -3, -4, -5) on a pilot site of Natural Forest Park in Guemsan-gun, Chungcheongbook-do, Korea. The regional lineaments of NW-SE are primarily developed on the area, which results in the development of many fractures of NW-SE direction around boreholes made in the test site for the study. A series of surface geological survey, core logging, geophysical logging, tomography, tracer tests, and heat-pulse flowmeter logging were carried out to determine fracture characteristics and fracture connectivity between the boreholes. In the result of fracture connectivity analysis BH-1 the injection well has a poor connectivity with BH-2 and BH-3, whereas a good with BH-4 and BH-5. In order to analyse the hydraulic connectivity between BH-1 and BH-5, in particular, a conspicuous groundwater outflux in the depth of 12 m and influx in the depth of 65 m and 70 m, but partly in/outflux occurred in other depths in BH-5 were observed as pumping from BH-1. On the other hand, when pumping from BH-5 the strong outflux in the depths of 17 m and 70 m was occurred. The spatial connectivity between the boreholes was examined in the depth of 15 m, 67 m, and 71 m in BH-1 as well as in the depth of 15 m, 17 m, 22 m, 72 m, and 83 m in BH-5.

• Journal of Korean Society of Water and Wastewater
• /
• v.21 no.4
• /
• pp.493-501
• /
• 2007

The membrane pilot plant has being operated in the Hyeondo pumping station to find the optimal operation technique of Gong-Ju membrane water treatment plant (WTP) which is constructing in $250m^3/d$ scale. The pilot plant was consisted of two trains which can treat $30,000m^3/d$ per train. First train was operated for one year under the condition of flux $1m^3/m^2{\cdot}d$ while the effects of flux variation and addition of powdered activated carbon(PAC) were evaluated in second train. The turbidity of membrane product water of first train which is operated on Flux $1m^3/m^2{\cdot}d$ was always below 0.05 NTU regardless of raw water turbidity. And also, the trance-membrane pressure(TMP) was maintained at $0.3{\sim}0.5kgf/cm^2$ for about 9 months and increased rapidly to $1.8kgf/cm^2$ which is maximum operating TMP. However, TMP was rapidly increased to $1.8kgf/cm^2$ within 2 months as flux was increased from 1 to $2m^3/m^2{\cdot}d$, especially, within 10 days under high turbidity(30~50NTU). This reault means that if Gongju membrane WTP is operated in flux $1m^3/m^2{\cdot}d$, chemical cleaning period can be maintained over 6 months. Only 10% of dissolved organic carbon (DOC) was removed in membrane process while the removal efficiencies of manganese and iron were 60% and 77% respectively. However, because only solid manganese and iron were removed in membrane process, an additional process for treating soluble manganese is required if souble manganese is high in raw water. 70% of 70ng/L 2-MIB which is causing taste & odor was removed in powdered activated carbon (PAC) tank with 50mg/L PAC which is design concentration of Gongju WTP. In addition, TMP was reduced with addition of 50mg/L PAC regardless of flux. Because TMP was not influenced even if 100mg/L PAC was added, the high taste and odor problem can be controled by additional injection of PAC.

• Journal of Korean Society of Environmental Engineers
• /
• v.28 no.6
• /
• pp.603-612
• /
• 2006

The study with laboratory sandbox model has been carried out to address potential use of reclaimed water, as a way for artificially recharging the coastal aquifer, to effectively prevent from seawater intrusion. To do this, we assessed hydraulic and geochemical properties depending upon various extraction and recharging conditions. While solely being recharged, the intrusion could be significantly retarded than those of recharge and extraction implied together. At 0.5 to 2 for the ratio of the extraction over the recharge rate, the fresh water was exploited from the tank, where the void regime was simultaneously saturated with the recharged water. In the meantime, the saline water zone was diluted and back-tracked by the recharged water due to forming a hydraulic geochemical barrier around the injection well. However, if the ratio was being increased to greater than 4, saltwater more deeply intruded to the freshwater zone because the artificial recharge was not sufficiently supplied to timely back-fill the void space. When the aquifer water was intermittently extracted at the ratio of $0.5{\sim}2$ over the recharge rate, the value of S.M.I. decreased, but increasing it to more than 4 unlikely escalated the value of S.M.I as much as $3{\sim}47%$ indicating that the salt water intruded. It finally revealed that the proper ratio of extraction/recharge or intermittent extraction would efficiently retracted seawater intrusion while the freshwater sources could be conservatively utilized.