• 자원환경지질
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• 제55권1호
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• pp.111-125
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• 2022

산사태가 발생하면 많은 시설에 큰 위험을 초래할 수 있기 때문에, 이를 예방하기 위해 사면의 특성을 상세하게 조사하고 불안정한 사면에 대해서는 적절히 보강을 수행해야 한다. 물리탐사는 사면을 교란시키지 않고 비교적 저렴한 비용으로 넓은 영역의 특성을 조사할 수 있는 방법으로, 외국에서는 사면의 안정성 조사에 널리 쓰이고 있는 반면 국내에서는 물리탐사 외의 직접적인 조사 방법들이 주로 쓰이고 있다. 이 논문에서는 물리탐사를 이용하여 사면의 특성을 파악하여 안정성을 평가한 사례들을 분석하고자 한다. 먼저 불안정한 사면물질, 균열 위치 및 연결성, 지하수위 분포에 따른 물성의 변화 등을 알아본 뒤, 이러한 물성 변화를 파악하기 위해 적용된 물리탐사 기법들인 전기비저항 탐사, 탄성파 탐사를 비롯해 자연전위 탐사, 유도분극 탐사, 지표투과레이더 탐사 등의 적용법에 대해 알아본다. 이에 기초하여, 기존의 여러 사면에서 실제로 수행되었던 물리탐사 사례들을 분석하였다.

• 한국농공학회논문집
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• 제58권2호
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• pp.31-44
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• 2016

This study analyzed pore water pressure, earth pressure and settlement through field monitoring on the project site in which raising embankments are being built through backside extension, and compared the behaviors of seepage analysis, slope stability analysis and stress-strain during flood water levels and rapid drawdown under steady state and transient condition. The variation of pore water pressure showed an increase during the later period in both upstream and downstream slope, with downstream slope more largely increased than upstream slope overall. The variation of earth pressure increased according to the increase of embankment heights, while the change largely showed in the upstream slope, it was slowly increased in the downstream slope. The settlements largely increased until 23 m as embankment heights increased, and showed very little settlement overall. Under a steady state and transient conditions, the seepage quantity per day and leakage quantity per 100 m of embankment against total storage were shown to be stable for piping. The hydraulic gradient at the core before and after raising embankments was greater than the limit hydraulic gradient, showing instability for piping. The safety factor of upstream and downstream slopes were shown to be very large at a steady state, while the upstream slopes greatly decreased at a transit conditions, downstream slopes did not show any significant changes. The horizontal settlements, the maximum shear strain and stress are especially distributed at the connecting portion of the existing reservoir and the new extension of backside. Accordingly, the backside extension method should be designed and reinforced differently from the cases of other types reservoirs.

• 한국지반공학회지:지반
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• 제5권1호
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• pp.27-34
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• 1989

이 연구는 지진이 일어나는 동안 균질토의 사면에 대한 확률론적 해적이다. 사면의 안정은 전통적인 안전율 보다는 파괴확률로써 측정된다. 최대지반가속도는 Donovan과 McGuire식을 사용하였다 지진크기는 무작위변수로 취급하였으며 이의 확률분포는 Richter의 법칙을 사용하여 얻어진다. 사면의 파괴면은 대수나선곡선으로 고려하였다. 통계적으로 균질한 흙의 사면에서 파괴면을 따라 흙의 전단강도 정수의 불확실정은 1차원 Random Field Model을 사용하여 나타냈으며 확률분포의 평균과 분산은 1차근사해석(wrist-order approximate analysis) 방법으로 계산하였다. 중요한 지진 계수들이 사면의 파괴확률에 미치는 영향에 대하여 검토하였고 그 결과가 그림이나 표에서 보여준다. 이 결과에서 다음과 같은 결론을 얻었다.

• 한국지반환경공학회 논문집
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• 제22권7호
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• pp.5-12
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• 2021

The reliable seismic stability evaluation of the natural slopes and geotechnical structures has become a critical factor of the design. Pseudo-static or permanent displacement methods are typically employed to evaluate the seismic slope performance. In both methods, the effect of input ground motion on the sliding surface is ignored, and failure surface from the limit equilibrium method is used. For the assessment of the seismic sensitivity of failure surface, two-dimensional non-linear finite element analyses are performed. The performance of the finite element model was validated against centrifuge measurements. A parametric study with a range of input ground motion was performed, and numerical results were used to assess the influence of ground motion characteristics on the sliding surface. Based on the results, it is demonstrated that the characteristics of input ground motion have a significant influence on the location of the seismically induce failure surface. In addition to dynamic analysis, pseudo-static analyses were performed to evaluate the discrepancy. It is observed that sliding surfaces developed from pseudo-static and dynamic analyses are different. The location of the failure surface change with the amplitude and T_m of motion. Therefore, it is recommended to determine failure surfaces from dynamic analysis

• 한국지반공학회지:지반
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• 제13권5호
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• pp.101-124
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• 1997

The root pile system is insitu soil reinforcement technique that uses a series of reticulately installed micropiles. In terms of mechanical improvement by means of grouted reinform ming elements, the root pile system is similar to the soil nailing system. The main difference between root piles and soil nailing are due to the fact that the reinforcing bars in root piles are normally grouted under high pressure and that the alignments of the reinforcing members differ. Recently, the root pile system has been broadly used to stabilize slopes and retain excavations. The accurate design of the root pile system is, however, a very difficult tass owing to geometric variety and statical indetermination, and to the difficulty in the soilfiles interaction analysis. As a result, moat of the current design methods have been heavily dependent on the experiences and approximate approach. This paper proposes a quasi-three dimensional method of analysis for the root pile system applied to the stabilization of slopes. The proposed methods of analysis include i) a technique to estimate the change in borehole radium as a function of the grout pressure as well as a function of the time when the grout pressure is applied, ii) a technique to evaluate quasi -three dimensional limit-equilibrium stability for sliding, iii) a technique to predict the stability with respect to plastic deformation of the soil between adjacent root piles, and iv) a quasi -three dimensional finite element technique to compute stresses and dis placements of the root pile structure barred on the generalized plane strain condition and composite unit cell concept talon형 with considerations of the group effect and knot effect. By using the proposed technique to estimate the change in borehole radius as a function of the grout pressure as well as a function of the time, the estimations are made and compar ed with the Kleyner 8l Krizek's experimental test results. Also by using the proposed quasi-three dimensional analytical method, analyses have been performed with the aim of pointing out the effects of various factors on the interaction behaviors of the root pile system.

• Geomechanics and Engineering
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• 제17권1호
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• pp.109-118
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• 2019

The movement of soil along a slope during rainfall can cause serious economic damage and can jeopardize human life. Accordingly, predicting slope stability during rainfall is a major issue in geotechnical engineering. Due to rainwater penetrating the soil, the negative pore water pressure will decrease, in turn causing a loss of shear strength in the soil and ultimately slope failure. More seriously, many constructions such as houses and transmission towers built in/on slopes are at risk when the slopes fail. In this study, the numerical simulation using 2D finite difference program, which can solve a fully coupled hydromechanical problems, was used to evaluate the effects of soil properties, rainfall conditions, and the location of a foundation on the slope instability and slope failure mechanisms during rainfall. A slope with a transmission tower located in Namyangju, South Korea was analyzed in this study. The results showed that the correlation between permeability and rainfall intensity had an important role in changing the pore water pressure via controlling the infiltrated rainwater. The foundation of the transmission tower was stable during rainfall because the slope failure was estimated to occur at the toe of the slope, and did not go through the foundation.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 추계 학술발표회
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• pp.1029-1037
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• 2008

The finite element analysis of transient water flow through unsaturated soils was used to investigate effects of hydraulic characteristics, initial relative degree of saturation, methods to consider boundary condition, and rainfall intensity and duration on water pressure in slopes. The finite element method with shear strength reduction technique was used to evaluate the stability of slopes under rainfall. The slope-related disasters in Korea usually occur between July and September during the typhoon and localized heavy rain. This means that the rainfall is the most important factor that leads to the slope-related disasters. The slope-related disasters can happen at very short time and lead to big damage. To forecast the change of the heave of the groundwater in slope the Seep/w program was used.

• 한국환경복원기술학회지
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• 제10권1호
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• pp.100-113
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• 2007

In Korea, there has been no revegetation applicable standard for slopes formed by road construction work up to now, so revegetation work has been done using mostly foreign varieties in the manner of early revegetation. However, foreign varieties have some shortcomings; for example, they tend to be dried to death after construction work. Besides, due to the rift in the supporting soil, these revegetated varieties are often displaced from the slopes. Thus, the Ministry of Construction & Transportation on July, 2005 established revegetation standard on the slopes suited for the natural eco-system of Korea and organized positively recommending directions for using self-sewn plants growing near the slopes in overall consideration of soil, weather, regional conditions. The locations specified in this direction are the slopes at the road construction jobsite like the expressway, highways, and local roads. In addition, the Ministry's standard and directions stipulated that damaged slopes's natural environment and eco-system due to various road construction work should be restored, and thus a feeling of stability and pleasantness should be provided to road users as well. Also, the Ministry tried to select seed plants and revegetation measures suited for surrounding environment to put the environment-friendly slope revegetation measures into practice through the test revegetation work in order to prevent illegal construction practices and to improve the quality of revegetation. According to the direction, revegetation districts aimed at the slopes are divided into three ones in consideration of weather environment, regional environment, and forest environment as follows : national territory's core ecological green-land based district centering on the Taebaek Mountains; coastal ecosystem district including islands off the coast; inland eco-system district. The combination of revegetation plants according to environment revegetation districts, should be executed by dividing into herb-oriented type, woody plant colony type, and bio-species versatility restoration type, and the selection of seeding plants should be done in the presence of a supervisor and through test construction results and technology counseling from a specialist in natural eco-system restoration and revegetation measure seed combination standard according to environment revegetation districts. This direction will be executed in the manner of monitoring until the yea 2008 and 2009 it will be finalized and enforced on December, 2009.

• 한국농공학회논문집
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• 제65권5호
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• pp.1-11
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• 2023

Due to climate change and aging of reservoirs, damage to embankment slopes is increasing. However, the safety diagnosis of the reservoir slope is mainly conducted by visual observation, and the time and economic cost are formidable to apply soil mechanical tests and slope stability analysis. Accordingly, this study presented a predicting method for the compaction and strength characteristics of the reservoir embankment soil using a portable static cone penetration test. The predicted items consisted of dry density, cohesion, and internal friction angle, which are the main factors of slope stability analysis. Portable static cone penetration tests were performed at 19 reservoir sites, and prediction equations were constructed from the correlation between penetration resistance data and test results of soil samples. The predicted dry density and strength parameters showed a correlation with test results between R² 0.40 and 0.93, and it was found to replace the test results well when used as input data for slope stability analysis (R² 0.8134 or more, RMSE 0.0320 or less). In addition, the prediction equations for the minimum safety factor of the slope were presented using the penetration resistance and gradient. As a result of comparing the predicted safety factor with the analysis results, R² 0.5125, RMSE 0.0382 in coarse-grained soil, R² 0.4182 and RMSE 0.0628 in fine-grained soil. The results of this study can be used as a way to improve the existing slope safety diagnosis method, and are expected to be used to predict the characteristics of various soils and inspect slopes.

• 한국지반공학회논문집
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• 제20권7호
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• pp.159-169
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• 2004

얕은사면 파괴는 지표로 침투하는 강우에 의해 주로 발생한다. 이는 지표수의 침투시 모관흡수력의 감소에 의한 포화깊이 증가에 의해 발생한다. 본 연구에서는 국내의 전형적인 화강풍화토를 대상으로 강우시 사면에서의 습윤영향을 분석하였다. 이를 위하여 filter paper와 tensiometer 실험을 수행하여 함수특성곡선을 산정하였으며, 그에 따른 함수특성곡선의 방정식을 추정하였으며, 기존에 사용되고 있는 Green & Ampt의 포화 깊이 추정식과 수치해석결과를 비교 분석하였다. 본 연구 결과, Green & Ampt모델에 의한 이론 해는 포화깊이를 과소 추정하였으며, 포화깊이가 증가함에 따라 사면안전율은 감소하는 것으로 나타났다. 특히 포화깊이가 약 1.2m이상부터 사면안전율은 현저하게 감소하는 것으로 나타났다.