침투해석을 고려한 비탈면 설계에 대한 연구

김유성,김재홍,이진광,김성수 한국지반공학회 2013 한국지반공학회논문집 Vol.29 No.1

Most of slope failures are triggered by heavy rainfall during rainy season. If the rain keeps on for the season, the water content of the ground increases and its matric suction decrease, and then the safety factor of soil slope gets lower. The change of water table level for soil slope stability dose not describe the behavior of the soil slope in real situation,hence it may be necessary to modify the design standard for slope stability in association with rain infiltration. For correct design, economical construction, and maintenance of a soil slope, unsaturated flow analysis is needed for estimation of slope instability regarding water infiltration and soil behavior on unsaturated soil slopes. The entire soil slope cannot be saturated by prolonged rainfall and wetting band depth (saturated zone) just deepens from slope surface,hence the cause of the shallow surface slide is the wetting band depth depending on rainfall duration and intensity. Therefore, the paper presents the differences between theoretical equation and numerical analysis for wetting band depth on soil surface and its safety factor, and compares the slope stability obtained from unsaturated flow analysis with that obtained from conventional slope stability analysis.

강우지속시간에 따른 풍화토사면의 개량토 심도 평가

유진주,이종우,이강일,Yu, Jin-Ju,Lee, Jong-Woo,Lee, Kang-Il 한국지반신소재학회 2022 한국지반신소재학회 논문집 Vol.21 No.2

Recently, irregular torrential rainfall have frequently occurred due to abnormal climate, and landslide damage is increasing. In Korea, more than 70% of the total land is mountainous areas, appropriate measures are needed to prevent landslides by heavy rainfall. When improved soil is applied to the surface of the slope, it is possible to suppress an increase in groundwater level due to rainfall penetration and secure stability of the slope. In this study, the appropriate depth of improved soil that can confirm the increase in groundwater level and secure stability by applying improved soil to the weathered soil slope was studied. A total of three cases were analyzed for the slope of the cross-section: standard slope for weathered soil (1:1.5, 1:1.8, and 1:2.0). For rainfall conditions, referring to the regional frequency probability rainfall provided by the Water resource Management Information System, the increase in groundwater level by stage was confirmed by assuming a 500-year frequency precipitation maximum duration of 48 hours. As a result of the study, in the case of natural slopes, the slope was completely saturated before 48 hours the rainfall duration, and there was a possibility of collapse. the improvement depth in the slope of 1:1.5 was appropriate for more than 1m from the surface regardless of the rainfall duration, and in the the slope of 1:1.8 was appropriate of 1m for more than 36 hours. in the slope of 1:2.0, it was appropriate for that safety when improved soil of 0.5m for rainfall duration 48 hours or more.

침투를 고려한 사면안정과 보강에 따른 안정성비교

이진광(Jin-Kwang Lee),김유성(You-Seong Kim),김재홍(Jae-Hong Kim) 한국지반신소재학회 2012 한국토목섬유학회 학술발표회 Vol.2012 No.11

Most slope failure occurs due to heavy rainfall during rainy season. For rainfall duration in the season, the safety factor of soil slope gets lower because the water content of the ground increases and the matric suction of that decrease. The change of water table level at the slope almost does not affect on the safety factor of a slope and then, it also may be necessary to modify the design standard for slope stability. In order to secure design, construction, and maintenance of a soil slope, the slope instability needs to estimate rainfall infiltration and soil behavior on unsaturated soils. The entire soil slope can not be saturated by prolonged rainfall and the saturated zone just deepened at slope surface due to it. Hence the shallow slip surface occurs depending on the influence of rainfall duration and intensity. The paper presents the differences between theoretical equation and numerical analysis for saturated depth on soil surface and the safety factor, and the slope stability obtained from infiltration analysis on unsaturated soil compares with that obtained from conventional slope stability analysis.

Modeling Soil Temperature of Sloped Surfaces by Using a GIS Technology

Jin I. Yun,S. Elwynn Taylor 韓國作物學會 1998 한국작물학회지 Vol.43 No.2

Spatial patterns of soil temperature on sloping lands are related to the amount of solar irradiance at the surface. Since soil temperature is a critical determinant of many biological processes occurring in the soil, an accurate prediction of soil temperature distribution could be beneficial to agricultural and environmental management. However, at least two problems are identified in soil temperature prediction over natural sloped surfaces. One is the complexity of converting solar irradiances to corresponding soil temperatures, and the other, if the first problem could be solved, is the difficulty in handling large volumes of geo-spatial data. Recent developments in geographic information systems (GIS) provide the opportunity and tools to spatially organize and effectively manage data for modeling. In this paper, a simple model for conversion of solar irradiance to soil temperature is developed within a GIS environment. The irradiance-temperature conversion model is based on a geophysical variable consisting of daily short- and long-wave radiation components calculated for any slope. The short-wave component is scaled to accommodate a simplified surface energy balance expression. Linear regression equations are derived for 10 and 50 cm soil temperatures by using this variable as a single determinant and based on a long term observation data set from a horizontal location. Extendability of these equations to sloped surfaces is tested by comparing the calculated data with the monthly mean soil temperature data observed in Iowa and at 12 locations near the Tennessee - Kentucky border with various slope and aspect factors. Calculated soil temperature variations agreed well with the observed data. Finally, this method is applied to a simulation study of daily mean soil temperatures over sloped corn fields on a 30 m by 30 m resolution. The outputs reveal potential effects of topography including shading by neighboring terrain as well as the slope and aspect of the land itself on the soil temperature.

Study on the Moisture and Thermal Characteristics of Vegetated Expansive Soil Slopes

Quan Shen,Yidan Zhang,Canrong Xie,Chengli Zhang,ChaoHui Wang 대한토목학회 2024 KSCE Journal of Civil Engineering Vol.28 No.6

The moisture and thermal characteristics of expansive soil slopes have a significant impact on the strength and overall stability of the soil. In this study, the medium-strength expansive soil vegetated slope in Baise, Guangxi, was taken as the research object. Through the combination of numerical simulation and measured meteorological data, the impact of moisture and heat characteristics on slope stability was then analyzed, and optimal geometric parameters conducive to the stability of vegetated slopes were proposed based on these findings. The research results indicate that under long-term climatic conditions, solar net radiation has the most sensitive effect on the evaporation of slope soil. During the evaporation process, vegetation transpiration dominates in the vegetation-covered layer, while below the depth of the vegetation cover layer, soil evaporation itself plays a dominant role. Under the conditions of evaporation-rainfall-evaporation, slopes with a smaller permeability coefficient in the vegetation cover layer have significantly higher safety factors than slopes with a larger permeability coefficient and bare slopes. A steep vegetated slope with a slope gradient of 50° can maintain slope stability with proper handling of its height. The research findings have reference value for the design and construction of vegetated slopes with expansive soil.

Reliable Assessment of Rainfall-Induced Slope Instability

김윤기,최정찬,성주현,이승래 한국지반공학회 2009 한국지반공학회논문집 Vol.25 No.5

Many slope failures are induced by rainfall infiltration. A lot of recent researches are therefore focused on rainfall-induced slope instability and the rainfall infiltration is recognized as the important triggering factor. The rainfall infiltrates into the soil slope and makes the matric suction lost in the slope and even the positive pore water pressure develops near the surface of the slope. They decrease the resisting shear strength. In Korea, a few public institutions suggested conservative slope design guidelines that assume a fully saturated soil condition. However, this assumption is irrelevant and sometimes soil properties are misused in the slope design method to fulfill the requirement. In this study, a more relevant slope stability evaluation method is suggested to take into account the real rainfall infiltration phenomenon. Unsaturated soil properties such as shear strength, soil-water characteristic curve and permeability for Korean weathered soils were obtained by laboratory tests and also estimated by artificial neural network models. For real-time assessment of slope instability, failure warning criteria of slope based on deterministic and probabilistic analyses were introduced to complement uncertainties of field measurement data. The slope stability evaluation technique can be combined with field measurement data of important factors, such as matric suction and water content, to develop an early warning system for probably unstable slopes due to the rainfall.

탄성파 탐사를 활용한 산지사면 토심 추정 및 예측모델 보정

봉태호,임상준,서정일,김동엽,허준 한국산림과학회 2023 한국산림과학회지 Vol.112 No.3

Landslides are major natural geological hazards that cause enormous property damage and human casualties annually. The vulnerability of mountainous areas to landslides is further exacerbated by the impacts of climate change. Soil depth is a crucial parameter in landslide and debris flow analysis, and plays an important role in the evaluation of watershed hydrological processes that affect slope stability. An accurate method of estimating soil depth is to directly investigate the soil strata in the field. However, this requires significant amounts of time and money; thus, numerous models for predicting soil depth have been proposed. However, they still have limitations in terms of practicality and accuracy. In this study, 71 seismic survey results were collected from domestic mountainous areas to estimate soil depth on hill slopes. Soil depth was estimated on the basis of a shear wave velocity of 700 m/s, and a database was established for slope angle, elevation, and soil depth. Consequently, the statistical characteristics of soil depth were analyzed, and the correlations between slope angle and soil depth, and between elevation and soil depth were investigated. Moreover, various soil depth prediction models based on slope angle were investigated, and corrected linear and exponential soil depth prediction models were proposed.

광산지역 비소오염 경사 농경지 토양의 안정화 및 유실 저감을 위한 석탄광산배수슬러지의 적용성 평가

고일하,권요셉,정문호,지원현,Koh, Il-Ha,Kwon, Yo Seb,Jeong, Mun-Ho,Ji, Won Hyun 한국지하수토양환경학회 2021 지하수토양환경 Vol.26 No.6

Soil aggregation begins with flocculation of clay particles triggered by interfacial reactions of polyvalent cation such as Ca²⁺ and Fe³⁺, and they are also known as important elements to control the mobility of arsenic in soil environment. The objective of this study was to investigate the feasibility of CMDS (coal mine drainage sludge) for soil loss reduction and stabilization of arsenic-contaminated soil in a 37% sloped farmland under rainfall simulation. The amount of soil loss decreased by 43% when CMDS was applied, and this result was not significantly different from the case of limestone application, which yielded 46% decrease of soil loss. However, the relative amount of dispersed clay particles in the sediment CMDS-applied soil was 10% lower than that of limestone-applied soil, suggesting CMDS is more effective than limestone in inducing soil aggregation. The concentrations of bioavailable arsenic in CMDS amended soil decreased by 46%~78%, which was lower than the amount in limestone amended soil. Therefore, CMDS can be used as an effective amendment material to reduce soil loss and stabilize arsenic in sloped farmland areas.

Steep Slope Stability Assessment Based on Hydrological Characteristics

Young Karb Song,Dongwook Kim 위기관리 이론과 실천 2015 Crisisonomy Vol.11 No.9

Each year, steep slope failures occur frequently because inopportune combinations of intensity and duration of rainfall trigger instability of the slopes. An Examination of effects of these two important rainfall factors on steep slope failure is a priority to prevent severe damage of properties and loss of lives resulting from slope failures. Slope failures are often triggered by a wetting band deepening caused by a decrease in matric suction due to water infiltration from the slope surfaces. The existing slope failure warning system in Korea does not reflect mechanical or hydraulic characteristics of unsaturated soils. In this study, geotechnical properties of unsaturated weathered soil, including permeability, soil-water characteristics curve, and shear strength, were examined by a series of experiments to evaluate slope stability. A procedure of steep slope failure risk evaluation is developed to reflect rainfall intensity, rainfall duration, and the mechanical and hydraulic properties of unsaturated soils.

깊이별 지반특성변화가 강우침투에 의한 사면표층 파괴에 미치는 영향

박가현,김지영,정충기,김경석 한국지반공학회 2014 한국지반공학회논문집 Vol.30 No.6

Intensive rainfall causes frequent slope failures at the shallow depths of slopes. Because soil layers at shallow depthsof slopes usually become dense, and its permeability and soil strength vary according to depth, forensic studies andstability analyses of shallow slope failure need to consider the depth-variant soil properties. In this study, the effectof depth-variant soil properties on surface failure of slopes during rain infiltration is investigated using numericalanalysis. Three different cases considering depth-variant soil properties were conducted and the results were compared. For the analysis, undisturbed soils at three different depths were sampled at actual slope failure sites and the propertiesincluding strength and permeability characteristics at each depth were obtained. Stability analysis and seepage analysiswere conducted using actual rainfall records. The comparison of the results shows that analysis could lead to anerroneous conclusion according to the way of considering depth-variant soil properties. The case in which depth-variantsoil properties were considered predicted similar failure times and failure shapes to the actual failure. Therefore itis recommended that the depth-variant soil properties should be considered for the analysis of shallow slope failureduring rain infiltration.