• Journal of Korean Society of Water and Wastewater
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• v.28 no.1
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• pp.33-45
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• 2014

In this study, current sewer infiltration/Inflow(I/I) computation and application method was examined about improvement and adequacy relating to the main issues raised by the field for practitioners. The results of review about infiltration calculation method were considered to be in need of improvement at 'standards of minimum sewage calculation'. Furthermore, the results of review about I/I application method were considered to be in need of improvement at 'standards of seasonal infiltration application' and 'the relative decrease in the Annual evaluation standards'. In addition, annual I/I analysis at JC County for the four years(2009~2012) in respect of operation flow and rainfall data was conducted. The result of annual infiltration analysis, compared average daily sewage generated average infiltration rate was found in 21.95 %, infiltration by unit was found in $0.31m^3/day/cm/km$ and $0.12m^3/day/day$, respectively. The result of annual inflow analysis, average rainfall - Inflow equations was found $y=5.499{\times}$($R^2$ 0.793), and the average Inflow quantity by sewer extension was predicted to $0.66m^3/mm-km$.

• The Journal of Engineering Geology
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• v.21 no.2
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• pp.133-145
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• 2011

Unsaturated soil column tests were performed for weathered gneiss soil and weathered granite soil to assess the relationship between infiltration velocity and rainfall condition for different rainfall durations and for multiple rainfall events separated by dry periods of various lengths (herein, 'rainfall break duration'). The volumetric water content was measured using TDR (Time Domain Reflectometry) sensors at regular time intervals. For the column tests, rainfall intensity was 20 mm/h and we varied the rainfall duration and rainfall break duration. The unit weight of weathered gneiss soil was designed 1.21 $g/cm^3$, which is lower than the in situ unit weight without overflow in the column. The in situ unit weight for weathered granite soil was designed 1.35 $g/cm^3$. The initial infiltration velocity of precipitation for the two weathered soils under total amount of rainfall as much as 200 mm conditions was $2.090{\times}10^{-3}$ to $2.854{\times}10^{-3}$ cm/s and $1.692{\times}10^{-3}$ to $2.012{\times}10^{-3}$ cm/s, respectively. These rates are higher than the repeated-infiltration velocities of precipitation under total amount of rainfall as much as 100 mm conditions ($1.309{\times}10^{-3}$ to $1.871{\times}10^{-3}$ cm/s and $1.175{\times}10^{-3}$ to $1.581{\times}10^{-3}$ cm/s, respectively), because the amount of precipitation under 200 mm conditions is more than that under 100 mm conditions. The repeated-infiltration velocities of weathered gneiss soil and weathered granite soil were $1.309{\times}10^{-3}$ to $2.854{\times}10^{-3}$ cm/s and $1.175{\times}10^{-3}$ to $2.012{\times}10^{-3}$ cm/s, respectively, being higher than the first-infiltration velocities ($1.307{\times}10^{-2}$ to $1.718{\times}10^{-2}$ cm/s and $1.789{\times}10^{-2}$ to $2.070{\times}10^{-2}$ cm/s, respectively). The results reflect the effect of reduced matric suction due to a reduction in the amount of air in the soil.

• Journal of the Korean Geotechnical Society
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• v.29 no.12
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• pp.77-85
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• 2013

Unsaturated slopes experience infiltration during rainfall and become unstable when saturated. On the viewpoint of unsaturated effective stress, as matric suction decreases, both effective stress and shear strength decrease, which declines slope stability consequently. This study is focused on describing effective stress based on suction stress. The actual slope failures are simulated to calculate factors of safety in the field of finite element stress. In the residual soils of Hadong and Pohang, unsaturated properties are evaluated by laboratory tests. For unsaturated slopes, analyses of infiltration, stress and stability were performed to simulate actual failures. Based on unsaturated effective stress principle, the stability of actual slopes could be evaluated successfully. It is verified for the effective stress concept to be applicable to the engineering practice on slope design which considers infiltration by rainfall.

• Journal of Korean Society of Water and Wastewater
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• v.29 no.1
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• pp.107-122
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• 2015

The purpose of this study is to analyze the structural stability of pavement due to water infiltration at the road with infiltration trench as using the FEM(finite element analysis). Five cases for FEM is divided considering the amount of rainfall and rain duration time. The results of FEM show that the more rainfall in a short period time is faster the change of moisture content. Also, it is the proportional relationship between and changing area of moisture content of more than 40% due to rainfall. Case 3 and 4 are necessary to check the installation of infiltration trench because of moisture content of more than 40%, recovery time of initial moisture content, and changing area of more than 40%. Case 1,2, and 5 have no a significant effect on road pavement structure due to lower moisture content and shorter duration time of higher moisture content.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.811-818
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• 2005

Stability analyses on the 17 railroad cut-off soil slopes were carried out. The influences of rainfall infiltration on the slope stabilities were taken into account by seepage analyses using finite element method and by assuming ground water tables to be located adjacent to soil surface. The validity of those analyses were evaluated by comparing the slope failure characteristics between analysis results and the past failure records. The analyses were not appropriate to estimate the failure surface and the method considering only the increase of pore-water pressure (reduction of matric suction) as the influence of rainfall cannot appropriately estimate the surficial failures that occurred most of the cut-off soil slopes. For the better estimation of the surficial failure, the influence of water flows over slope surface which erode soil mass and/or increase driving force, should be evaluated and considered.

• Economic and Environmental Geology
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• v.44 no.1
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• pp.71-82
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• 2011

The unsaturated soil column tests were carried out for weathered gneiss soil and weathered granite soil in order to obtain the relationship between rainfall intensity and infiltration velocity of rainfall on the basis of different unit weight conditions of soil. In this study, volumetric water content and pore water pressure were measured using TDR sensors and tensiometers at constant time interval. For the column test, three different unit weights were used as in-situ condition, loose condition and dense condition, and rainfall intensities were selected as 20 mm/h and 50 mm/h. In 20 mm/h rainfall intensity condition, average rainfall infiltration velocities for both gneiss and weathered granite soils were obtained as $2.854{\times}10^{-3}$ cm/s ~ $1.297{\times}10^{-3}$ cm/s for different unit weight values and $2.734{\times}10^{-3}$ cm/s ~ $1.707{\times}10^{-3}$ cm/s, respectively. In 50 mm/h rainfall intensity condition, rainfall infiltration velocities were obtained as $4.509{\times}10^{-3}$ cm/s ~ $2.016{\times}10^{-3}$ cm/s and $4.265{\times}10^{-3}$ cm/s ~ $3.764{\times}10^{-3}$ cm/s respectively. The test results showed that the higher rainfall intensity and the lower unit weight of soil, the faster average infiltration velocity. In addition, the weathered granite soils had faster rainfall infiltration velocities than those of the weathered gneiss soils except for the looser unit weight conditions. This is due to the fact that the weathered granite soil had more homogeneous particle size, smaller unit weight condition and larger porosity.

• Proceedings of the Korean Geotechical Society Conference
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• 1998.10a
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• pp.329-336
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• 1998

• Journal of the Korean Society of Hazard Mitigation
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• v.4 no.4 s.15
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• pp.27-34
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• 2004

In this paper, in order to analyse the variation of runoff characteristics depending upon installation of the groundwater recharge facilities, the experiment basin was prepared and the ratio of infiltration and runoff volume were observed in the rainfall events. For the rainfall analysis, 4 types of rainfall events were examined during July 11${\sim}$July 17, 2004. The results show that the mean ratio of infiltration was 89.39% and the mean ratio of runoff was 10.61%. For the artificial rainfall events, which are in the range of rainfall intensities between 60mm/hr and 100mm/hr, all the rainfall volume was infiltrated through the groundwater recharging basin. However, it is necessary to be careful for the long term rainfall, the runoff can be occurred based on the groundwater table.

• Journal of the Korean Geotechnical Society
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• v.28 no.2
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• pp.71-78
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• 2012

Rainfall infiltration test under one dimensional condition is conducted to evaluate the effect of rainfall intensity on seepage velocity and infiltration characteristics for initial unsaturated sediment. Experimental results are compared with those numerical simulations with respect to variations of pore water pressure, degree of saturation and discharge velocity with time, and both results give good agreement. High rainfall intensity tends to increase seepage velocity almost linearly. But it shows rapid increase as rainfall intensity approaches saturated hydraulic conductivity of the sediment. In addition, the upper part of wetting front depth is partially saturated, not fully. Therefore, actual wetting front depth is considered to advance faster than theoretical prediction, which leads to slope instability of unsaturated slope due to surface rainfall.

• Journal of The Korean Society of Agricultural Engineers
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• v.54 no.5
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• pp.129-139
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• 2012

Accurate modeling rainfall induced landslide and slope stability requires a detailed knowledge of the distribution of material strength characteristics and suction distribution. However, material properties obtained from the drying cycle are still used for infiltration analysis in many cases, even though material properties of wetting cycle are quite different from those of drying cycle due to hydraulic hysteresis and air occlusion. Therefore, the selection of proper material properties such as soil-water retention curve (SWRC) and the hydraulic conductivity function (HCF) reflecting characteristics of wetting cycle and air occlusion is an essential prerequisite in order to simulate the infiltration phenomena and to predict the suction and water content distribution in unsaturated soils. It is concluded that the simulation of infiltration with material properties from the drying cycle did not reasonably match with experimental outputs. Further discussion is made on how to describe the material properties considering air occlusion during wetting cycle over the entire suction range in order to simulate infiltration phenomena.