• Title, Summary, Keyword: rainfall infiltration

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The Development of Rail-Transport Operation Control using the Variation of Slope Stability under Rainfall (강우시 사면안전율 변화를 이용한 열차운전규제기준 개발)

  • Kim, Hyun-Ki;Lee, Jin-Wook;Shin, Min-Ho
    • Proceedings of the KSR Conference
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    • pp.397-402
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    • 2003
  • Infiltration of rainfall causes railway embankment to be unstable and may result in failure. Basic relationship between the rainfall and stability of railway embankment are defined to analyze the stability of embankment by rainfall. An experimental study for defining of infiltration rate of rainfall into slope is conducted in the lab. The results of Rainfall infiltration show that rainfall infiltration is not equal to infiltration as like reservoir because rate of rainfall infiltration is controlled by slope angle. Based on these results, boundary condition of rainfall is altered and various numerical analysis are performed. The variation of shear strength, the degree of saturation and pore-water pressure for railway slope during rainfall can be predicted and the safety factor of railway slope can be expressed as the function of rainfall amount, namely rainfall index. Therefore, it is judged that this rainfall index can be a good tool for the rail-transport operation control.

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Rail Transport Operation Control for Railway Embankment under rainfall (강우시 성토사면의 열차운전규제기준)

  • Kim, Hyun-Ki;Shin, Min-Ho;Choi, Chan-Yong
    • Proceedings of the Korean Geotechical Society Conference
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    • pp.225-232
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    • 2009
  • Infiltration of rainfall causes railway slopes to be unstable and may result in failure. Basic relationship between the rainfall and stability of railway embankment is defined to analyze its stability by rainfall. An experimental study for defining of infiltration rate of rainfall into slope is conducted in the lab. The results of Rainfall infiltration show that rainfall infiltration is not equal to infiltration as like reservoir because rate of rainfall infiltration is controlled by slope angle. Based on these results, boundary condition of rainfall is altered and various numerical analysis are performed. The variation of shear strength, the degree of saturation and pore-water pressure for railway slope during rainfall can be predicted and the safety factor of railway slope can be expressed as the function of rainfall amount, namely rainfall index. And suggested rainfall index is compared with the rail transport operation control which is used in KORAIL. It is judged that this rainfall index can be a good tool for the rail-transport operation control.

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An Offer of a Procedure Calculating Hourly Rainfall Excess by Use of Horton Infiltration Model in a Basin (유역 단위 Horton 침투모형을 적용한 시간단위 초과우량 산출 절차 제시)

  • Yoo, Ju-Hwan
    • Journal of Korea Water Resources Association
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    • v.43 no.6
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    • pp.533-541
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    • 2010
  • It is basic for a flood prediction to calculate direct runoff from rainfall in a basin by the rainfall-runoff model. The direct runoff is calculated from rainfall excess or effective rainfall based on a rainfall-runoff model. The total rainfall minus rainfall loss equals rainfall excess with time. This loss can be treated equal to an infiltration loss under the assumption that the infiltration is a major one among the losses in the rainfall-runoff model. Practically obtaining the infiltration loss $\Phi$ index method, W index method or modified ones of these have been used. In this study it is assumed the loss of rainfall in a basin be a well-known Horton infiltration mechanism. And in case that the parameter set is given in the Horton infiltration model a procedure and assumption for calculating hourly infiltration loss and rainfall excess are offered and the results of its application are compared with those of $\Phi$ index method. By this study it is well shown the value of Horton infiltration function is exponentially decay with time as the Horton infiltration mechanism.

Application of Percentile Rainfall Event for Analysis of Infiltration Facilities used by Prior Consultation for LID (Low Impact Development)

  • Kwon, Kyung-Ho;Song, Hye-Jin
    • KIEAE Journal
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    • v.15 no.5
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    • pp.5-12
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    • 2015
  • Purpose: Retention and infiltration of small and frequently-occurring rainfall by LID facilities account for a large proportion of the annual precipitation volume. Based on 4 standard facilities such as Porous Pavement, Infiltration Trench, Cylindrical Infiltration Well, Rectangular Infiltration Well by Seoul Metropolitan Handbook of the Prior Consultation for LID. The total retention volume of each facility was calculated according to the type and size. The Purpose of this study is to find out the quantitative relationship between Percentile Rainfall Event and Design Volume of Infiltration Facilities. Methode: For the estimation of Percentile Rainfall Event, Daily Precipitation of Seoul from 2005 to 2014 was sorted ascending and the distribution of percentile was estimated by PERCENTILE spreadsheet function. The managed Rainfall Depth and Percentile of each facility was calculated at the several sizes. In response to the rainwater charge volume of 5.5mm/hr by the Category "Private large site", the 3 types of facilities were planned for example. The calculated Rainfall Depth and Percentile were 54.4mm and 90% by the use of developed Calculation-Module based on the Spreadsheet program. Result: With this Module the existing Designed Infiltration volume which was introduced from Japan was simply converted to the Percentile-Rainfall-Event used in USA.

Analysis of rainfall infiltration characteristics for unsaturated soils using a column test equipment (모형실험장치를 이용한 불포화토의 강우 침투특성 분석)

  • Park, Kyu-Bo;Chae, Byung-Gon;Kim, Kyeong-Su
    • Proceedings of the Korean Geotechical Society Conference
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    • pp.736-742
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    • 2010
  • This study was conducted to characterize on the relationships of rainfall intensity and infiltration rate of rainfall dependent on unit weight change in the gneissic weathered soil by a column test equipment. In this study, volumetric water content and pore water pressure were measured using TDR sensors and tensiometers at regular time intervals. Rainfall conditions including continuous rainfall and repeated rainfall were selected in order to know the effect of antecedent rainfall. In the condition of rainfall intensity 20mm/h and the unit weights of soil as $1.35g/cm^3$, $1.55g/cm^3$ and $1.61g/cm^3$, average rainfall infiltration rate was $2.814{\times}10^{-3}cm/sec$, $1.969{\times}10^{-3}cm/sec$ and $1.252{\times}10^{-3}cm/sec$ respectively. The higher rainfall intensity and lower unit weight of soil, the faster average infiltration rate. Overflow in the column was happened except rainfall condition of rainfall intensity 20mm and soil unit weight $1.35g/cm^3$. Increasing the soil unit weight, overflowed water was increased and occurrence time was faster.

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A Study on Development of Computer model for Evaluating the Effective Rainfall on Upland Soil (밭 토양에서의 유효강우량 산정을 위한 전산모델 개발에 관한 연구)

  • 고덕구;정하우
    • Magazine of the Korean Society of Agricultural Engineers
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    • v.24 no.1
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    • pp.63-72
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    • 1982
  • To maintain an optimum condition for the plant growth on upland soil, the irrigation planning after the natural rainfall should be given enormous considerations on the rainfall effectiveness. This study has been intended to develop the computer model for estimating the effec- tiveness of the rainfall. The computer model should also estimated the infiltration due to the rainfall and the soil moisture deficiency at the root zone of the plant. For this purpose, the experiments of infiltration using rainfall simulator and the observations of the change of soil moisture content before and after rainfall were carried out. Needed input data for the developed model include final infiltration capacity and field capacity of the soil, porosity of the top soil, root depth of the plant, rainfall intensity and duration, and the Horton's decay coefficient. Among the needed input data for the developed model, final infiltration capacity and Horton's decay coefficient were determined by the experiments of infiltration. And from the result of the experiments, it is found that there is a great correlation between initial infiltration capacity and initial moisture content. And it is also found that the infiltration due to rainfall can be estimated with the Horton's equation. The developed model was tested by the experimental data with two rainfall intensities. Tests were conducted on the different root depths at each rainfall. Observed and estimated effective rainfalls were found to have great correlation. The result of the experiments showed that the effectiveness of the rainfall were 100%, so the comparisons were conducted by the comsumption rates of infiltration at each depth. The developed model can be also used for estimating the deficiency of rainfall, if the rainfall is not sufficient to the needed soil moisture. But, test was not carried out.

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Infiltration characteristics and hydraulic conductivity of weathered unsaturated soils

  • Song, Young-Suk;Hong, Seongwon
    • Geomechanics and Engineering
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    • v.22 no.2
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    • pp.153-163
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    • 2020
  • Laboratory experiments were conducted with two different soil conditions to investigate rainfall infiltration characteristics. The soil layer materials that were tested were weathered granite soil and weathered gneiss soil. Artificial rainfall of 80 mm/hr was reproduced through the use of a rainfall device, and the volumetric water content and matric suction were measured. In the case of the granite soil, the saturation velocity and the moving direction of the wetting front were fast and upward, respectively, whereas in the case of the weathered gneiss soil, the velocity and direction were slow and downward, respectively. Rainfall penetrated and saturated from the bottom to the top as the hydraulic conductivity of the granite soil was higher than the infiltration capacity of the artificial rainfall. In contrast, as the hydraulic conductivity of the gneiss soil was lower than the infiltration capacity of the rainfall, ponding occurred on the surface: part of the rainfall first infiltrated, with the remaining rainfall subsequently flowing out. The unsaturated hydraulic conductivity function of weathered soils was determined and analyzed with matric suction and the effective degree of saturation.

Numerical Study of Unsaturated Infinite Slope Stability regarding Suction Stress under Rainfall-induced Infiltration Conditions

  • Song, Young-Suk;Hwang, Woong-Ki
    • The Journal of Engineering Geology
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    • v.24 no.1
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    • pp.1-8
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    • 2014
  • Numerical stability analysis of an unsaturated infinite slope under rainfall-induced infiltration conditions was performed using generalized effective stress to unify both saturated and unsaturated conditions The soil-water characteristic curve (SWCC) of sand with a relative density of 75% was initially measured for both drying and wetting processes. The hydraulic conductivity function (HCF) and suction stress characteristic curve (SSCC) were subsequently estimated. Under the rainfall-induced infiltration conditions, transient seepage analysis of an unsaturated infinite slope was performed using the finite element analysis program, SEEP/W. Based on these results, the stability of an unsaturated infinite slope under rainfall-induced infiltration conditions was examined in relation to suction stress. According to the results, the negative pore-water pressure and water content within the slope soil changed over time due to the infiltration. In addition, the variation of the negative pore-water pressure and water content led to a variation in suction stress and a subsequent change in the slope's factor of safety during the rainfall period.

The Development of Rail-Transport Operation Control based on Unsaturated Soil Mechanics Concept (불포화토이론을 이용한 강우시 열차운전규제기준 개발)

  • Kim, Hyun-Ki;Shin, Min-Ho;Kim, Soo-Sam
    • Journal of the Korean Society of Hazard Mitigation
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    • v.4 no.1
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    • pp.25-31
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    • 2004
  • Infiltration of rainfall causes railway embankment to be unstable and may result in failure. Basic relationship between the rainfall and stability of railway embankment is defined to analyze the stability of embankment by rainfall. An experimental study for defining of infiltration rate of rainfall into slope is conducted in the lab. The results of Rainfall Infiltration show that rainfall Infiltration is not equal to infiltration as like reservoir because rate of rainfall infiltration is controlled by slope angle. Based on these results, boundary condition of rainfall is altered and various numerical analysis are performed. The variation of shear strength, the degree of saturation and pore-water pressure for railway slope during rainfall can be predicted and the safety factor of railway slope can be expressed as the function of rainfall amount, namely rainfall index. Therefore, it is judged that this rainfall index can be a good tool for the rail-transport operation control.

Saturation Depth and Slope Stability considering Unsteady Rainfall in Natural Slope (비정상강우를 적용한 자연사면에서의 포화깊이 산정 및 사면안정성 평가)

  • Kim, Sang-Hoon;Kim, Seong-Pil;Son, Young-Hwan;Heo, Joon;Chang, Pyoung-Wuck
    • Journal of The Korean Society of Agricultural Engineers
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    • v.49 no.1
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    • pp.57-65
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    • 2007
  • In Korea, most landslides occurr during the rainy season and have shallow failure planes parallel to the slope. For these types of rainfall-induced failures, the most important factor triggering slope unstability is decrease in the matric suction of unsaturated soils with increasing saturation depth by rainfall infiltration. For this reason, estimation of cumulative infiltration has a significance. In this study, infiltration rate and cumulative infiltration are estimated by using both Mein & Larson model based on Green-Ampt infiltration model and using modified Mein & Larson model to which unsteady rainfall is applied. According to the results, the modified model is more reasonable than Mein & Larson method itself in estimation of infiltration rate and saturation depth because of considering real pending condition.