• Journal of Korean Society of Environmental Engineers
• /
• v.34 no.5
• /
• pp.359-364
• /
• 2012

In order to prevent the decrease in well efficiencies due to friction in the axial flow in long, large-diameter laterals, a multi-diameter lateral was devised and tested through lab-scale sand-box experiments to assess its performance. In the experiment, three different production rates were applied over the multi-diameter and the three single-diameter laterals to obtain the hydraulic head distributions for each, which was used to assess the performance of the laterals. Results elucidated that the multi-diameter lateral reduced the material cost by more than a third, in comparison to the single-diameter lateral, while maintaining the production rate at higher than 93%, proving its superiority. Furthermore, results indicated that exit velocities exceeding 0.8 m/sec in horizontal wells tended to distort the hydraulic head distribution near the exit, providing evidence of its inefficiency.

• Journal of Korean Society of Environmental Engineers
• /
• v.35 no.5
• /
• pp.334-339
• /
• 2013

A pilot-scale sand-box experiment simulating a lateral of collector well used in riverbank filtration was performed, and hydraulic head distributions along the lateral were measured according to the various drawdowns at the well. The results of this experiment were compared to the predicted values obtained using a theory previously developed by Kim in order for its validation. This theory predicts the head loss in a large-scale lateral given the loss in a small-scale one, and to have actual values for comparison, the results from a lab-scale experiment previously performed by Kim were employed. Comparing the experimental values to the extrapolated value indeed confirmed the validity of the theory. A procedure to determine the hydraulic head distribution of a practical-scale lateral was also presented applying the theory to the experimental result of this study in an effort to show the process of lateral design for riverbank filtration.

• Journal of Korean Society of Environmental Engineers
• /
• v.34 no.6
• /
• pp.430-437
• /
• 2012

In order to obtain information on the design parameters of the horizontal laterals in floodplain filtration, laboratory-scale sand-box experiments were performed where the head distributions on the laterals and the groundwater profiles were measured according to the change in parameters including lateral diameter, hydraulic conductivity of the sand, water level at the well and raw-water supply rate. Measured data were analyzed using a numerical code in order to identify the discharge intensity distribution along the laterals. It was observed from the result that the lowering of the water level at the well had minimal adverse effect on the performance of the floodplain filtration. Results also elucidated that the low conveyance of the laterals to transmit the filtrate was compensated and supplemented by a natural augmentation in horizontal conveyance through the aquifer when the raw-water supply rate exceeded the adequate recovery rate. With this mechanism, the water quality is expected to improve further since the travel distance through the aquifer is amplified. Based on these findings it can be suggested that the diameter of the lateral used in the floodplain filtration may be smaller than those in riverbank/bed filtration. It was also found that the ratio between the head loss occurring in a lateral and the total head loss in the floodplain filtration was proportional to the exit velocities of the laterals, which may be used to design and/or evaluate the lateral in floodplain filtration.

• Journal of Korean Society of Environmental Engineers
• /
• v.29 no.2
• /
• pp.176-183
• /
• 2007

In order to analyze the experimental results obtained from the model riverbed filtration performed by Ahn et al. a mathematical model was developed to simulate the flow through the lateral. The discharge rates at each section of the lateral measured by Ahn et al. were compared with the model predictions, and they matched favorably. The Manning's roughness coefficients of all the laterals employed in the study of Ahn et al. were determined using the model. Results show that the roughness coefficient becomes larger with the increase in the entrance velocity to the collector well, and that the coefficient ranges from 0.012 to 0.015 under the normal operational conditions of the riverbed filtration. Results also show that the coefficient becomes smaller as the lateral diameter increases.

• The Journal of Engineering Geology
• /
• v.26 no.3
• /
• pp.331-337
• /
• 2016

Radial collector wells (RCWs) have been managed by Korea Rural Community Corporation (KRC) since 1983, installing 98 wells for agriculture in rural area over the country. Among them, 20 wells were installed upstream of 5 subsurface dams and the remaining were installed regardless of the subsurface dam. Most of RCWs have been developed in 1980s and 1990s, and 83 wells have been passed more than 20 years after construction. The number of horizontal arms for RCWs varies from 9 to 28, with length and diameter being 10~30 m and 65 mm, respectively. The central caisson with an inner diameter of 3.5 m was commonly constructed to a depth of 10 m. The maximum pumping rates in RCWs, which are located at distances of 10 to 1,200 m from the river, are 2,000~10,000 m³/day. RCW has a fundamental problem that reduced pumping capacity and degraded well efficiency, due to the physical and chemical clogging. From the feasibility test for improving RCW performance, specific capacity increased to 67% after rehabilitation. TV logging for RCW horizontal arm shows that near the caisson is more severe clogging. From the results of this study, KRC has established the guidebook for monitoring and improving well efficiency through physical/chemical treatment, well logging, and hydraulic tests and managed RCWs periodically with its rehabilitation methods.

• Journal of Korean Society of Environmental Engineers
• /
• v.27 no.12
• /
• pp.1305-1310
• /
• 2005

As a way to the optimum design of the collector well lateral in riverbed filtration, experiments were performed using sand tanks which were connected to form a model lateral system. Measured were the residual hydraulic heads along the laterals, the discharge rates at each sand tank and the production rates at the collector well while the model laterals were operated with various scenarios of changing parameters including water level of the collector well, the lateral diameter and length, and the hydraulic conductivity of the sand. Results showed that riverbed filtration could be more efficient when the resistance in the lateral was weak compared with the resistance in the sand, which was indicated by the more flattened distribution of the residual hydraulic heads along the lateral. Results also showed that the discharge rate increased exponentially with the approach to the collector well, and that the exponent increased as the lateral diameter decreased and/or the hydraulic conductivity of the sand increased. It was also seen that the well production increased with the increase in the lateral length and diameter although the marginal productivity decreased. It could be concluded that the axial flow velocity in the lateral was an important factor governing the efficiency of a lateral in riverbed filtration and that the maximum entrance velocity to the collector well, over which the efficiency decreased drastically, was about 1 m/sec under the conditions of this study.

• The Journal of Engineering Geology
• /
• v.24 no.2
• /
• pp.201-215
• /
• 2014

This study was performed to investigate the correlation between hydraulic conductivity and the flow rate of an aquifer, with the flow rate calculated from the laterals of the radial collector well using data obtained by the development project of riverbank filtration (Second Phase) in Changwon City. The hydraulic conductivity was empirically calculated from unconsolidated sediments collected from a sandy gravel layer along the middle-to-downstream sections of the Nakdong River. The Beyer equation produced the most suitable hydraulic conductivity from the various empirical formulas employed. The calculated hydraulic conductivity ranged from 0.083 to 0.264 cm/s, with an average value of 0.159 cm/s, suggesting that the aquifer in the study area possesses a high permeability with a good distribution of sandy gravel. The relationship between the calculated hydraulic conductivity in the aquifer and the entrance velocity into the screen, the flow rate was analyzed through the linear regression analysis. From the result of regression analysis, it showed that the hydraulic conductivity and the entrance velocity into the screen and the flow rate have a linear regression equation having about 72% of the high correlation. The result of verification in the measured data between each variable showed a high suitability from being consistent with the approximately 72% in the linear regression analysis. This study demonstrates that the groundwater flow rate can be estimated within the laterals of the radial collector well using a linear regression equation, if the hydraulic conductivity of the aquifer is known. This methodology could thus be applicable to other aquifers with hydraulic conductivity and permeability parameters similar to those in the present study area.

• Journal of Korean Society of Environmental Engineers
• /
• v.28 no.8
• /
• pp.884-887
• /
• 2006

• The Journal of Engineering Geology
• /
• v.29 no.3
• /
• pp.279-288
• /
• 2019

The groundwater drawdown at each monitoring well near a radial collector well along Anseong Stream, Korea, was measured and compared with the calculated drawdown using the mirror well concept. The drawdown calculation is performed by treating the collector well as a large vertical well in a homogeneous isotropic aquifer. The measured drawdown at each monitoring well is slightly different from the calculated value due to anisotropy in the hydraulic conductivity and aquifer thickness. The difference between the measured and calculated values at Well OW-7 is large, reaching approximately 48 cm, because a horizontal well is not installed along this direction. Sensitivity analysis of the hydraulic conductivity and aquifer thickness indicates that the hydraulic conductivity is more sensitive to groundwater level changes. Groundwater level changes become a concern when a radial collector well with a large pumping rate capacity is installed, which highlights the need to thoroughly investigate the aquifer characteristics in the surrounding area.

• Journal of Korea Soil Environment Society
• /
• v.5 no.1
• /
• pp.75-83
• /
• 2000

Recently, many landfills are constructed by using geosynthetics with earth materials. Geotextiles in geosynthetics are applied for the various purposes such as filters of the leachate collection and removal system and protectors of geomembrane liner. However geotextiles can be exposed to direct sunlight during the construction of landfill for several months. As you know the exposure of polymers to sunlight can be a major source of degradation of them. This study is to suggest a criteria on the installation of heavy weight geotextiles at the landfill. For this purpose, several different geotextiles were evaluated by outdoor exposure at two different locations and under the different seasons for one and half years. As the results of outdoor exposure, polypropylene geotextiles with 500g/$m^2$ and 700g/$\textrm{m}^2$were maintained around 40% of the initial strength during for one and half years. However, the polypropylene geotextile of 1000g/$\textrm{m}^2$showed 65% of the retained strength for the same duration of exposure. The retained strength of all polypropylene geotextile reduced dramatically with the cumulative sunshine radiation on a horizontal surface of around 1500MJ/$\textrm{m}^2$.