국내 풍화토사면의 경우 순수 균질 사면보다는 대부분 점토 및 세립분이 섞인 비균질 상태로 존재하며 이러한 함유비율은 풍화도 및 지역에 따라 다르다. 따라서 세립분함량 변화에 따른 불포화사면에의 분석을 위해, 화강풍화토(SW)에 일정비율의 세립분(CH)을 섞어 성형한 시료를 통해 GCTS pressure plates을 이용한 함수특성곡선 실험을 수행하였다. 실험 및 침투해석결과 강우지속시간에 따른 포화깊이의 증가율은 세립분이 증가할수록 또한 상대밀도가 증가할수록 작아졌다. 또한 침투해석과 포화 및 불포화강도정수를 이용한 사면 안정성 해석결과(SLOPE/W), 전반적으로 세립분함량 $10\sim15%$의 범위까지는 침투깊이 증가에 따른 흡수력 변화가 안전율에 지대한 영향을 미치는 반면 이를 초과하는 경우(>15%)에는 오히려 세립분함량 증가에 따른 강도정수의 변화가 크게 영향을 미침을 알 수 있었다.
국내 풍화토사면의 경우 순수 균질 사면보다는 대부분 점토 및 세립분이 섞인 비균질 상태로 존재하며 이러한 함유비율은 풍화도 및 지역에 따라 다르다. 따라서 세립분함량 변화에 따른 불포화사면에의 분석을 위해, 화강풍화토(SW)에 일정비율의 세립분(CH)을 섞어 성형한 시료를 통해 GCTS pressure plates을 이용한 함수특성곡선 실험을 수행하였다. 실험 및 침투해석결과 강우지속시간에 따른 포화깊이의 증가율은 세립분이 증가할수록 또한 상대밀도가 증가할수록 작아졌다. 또한 침투해석과 포화 및 불포화강도정수를 이용한 사면 안정성 해석결과(SLOPE/W), 전반적으로 세립분함량 $10\sim15%$의 범위까지는 침투깊이 증가에 따른 흡수력 변화가 안전율에 지대한 영향을 미치는 반면 이를 초과하는 경우(>15%)에는 오히려 세립분함량 증가에 따른 강도정수의 변화가 크게 영향을 미침을 알 수 있었다.
In South Korea, many weathered soil slopes are composed of soil mixtures with certain amount of clay fractions in natural soil deposits. Accordingly, it is very important to analyze that effect of the fines on the stability of unsaturated soil slopes. In this study, five different soil types classif...
In South Korea, many weathered soil slopes are composed of soil mixtures with certain amount of clay fractions in natural soil deposits. Accordingly, it is very important to analyze that effect of the fines on the stability of unsaturated soil slopes. In this study, five different soil types classified by mixture portion of fines were used and experiment on the soil-water characteristic curve tests (SWCC) using GCTS (Geotechnical Consulting and Testing Systems) pressure plate were performed in order to analyze the stability of unsaturated soil slopes. Based on the infiltration analysis which contains SWCC test result by the SEEP/W, it is shown that the increasing rate of the wetting band depth was decreased as the fines content and the relative density were increased. According to the stability analysis result of the unsaturated soil slopes through the SLOPE/W, it is found that the transition from the wetting band depth to the variation of strength parameters which affect the stability of unsaturated soil slopes appears to occur around $10\sim15%$ of clay contents in the mixtures.
In South Korea, many weathered soil slopes are composed of soil mixtures with certain amount of clay fractions in natural soil deposits. Accordingly, it is very important to analyze that effect of the fines on the stability of unsaturated soil slopes. In this study, five different soil types classified by mixture portion of fines were used and experiment on the soil-water characteristic curve tests (SWCC) using GCTS (Geotechnical Consulting and Testing Systems) pressure plate were performed in order to analyze the stability of unsaturated soil slopes. Based on the infiltration analysis which contains SWCC test result by the SEEP/W, it is shown that the increasing rate of the wetting band depth was decreased as the fines content and the relative density were increased. According to the stability analysis result of the unsaturated soil slopes through the SLOPE/W, it is found that the transition from the wetting band depth to the variation of strength parameters which affect the stability of unsaturated soil slopes appears to occur around $10\sim15%$ of clay contents in the mixtures.
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문제 정의
These soils consist of soil mixture with certain amount of clay fractions in natural soil deposits. This paper describes the results of a series of soil-water characteristic curve tests and numerical analyses aimed at clarifying the effect of the magnitude of wetting band depth on unsaturated soil slopes. Special attention is given to the prediction of approximate limit of clay content which influences the magnitude of wetting band depth in soil mixtures.
가설 설정
(1) The volumetric water content decrement was decreased as the fines content of the each soil mixtures and the relative densities were increased. And the volumetric water content had critical distinction between SW100% and other soil mixtures (SW95%+CH5%, SW90%+ CH10%, SW85%+CH15%, SW80%+CH20%).
제안 방법
The total duration of rainfall is 96 hours. It was divided into 11 time stages (0.1, 0.5, 1, 2, 3, 5, 10, 24, 48, 72 and 96 hours) and wetting band depth was obtained for each of these stages. For simplicity, the intensity of rainfall was kept constant fbr the entire duration of rainfall.
대상 데이터
The pressure chamber is stainless steel and can be subjected to extremely high air pressure. The soil specimen is rammed into a stainless steel ring and placed on top of ttie high air entry ceramic stone. Different high air entry ceramic stones can be inserted into the base of the apparatus and used for different soil types.
The soils used in this study are weathered soil (SW) and clay soil (CH) in Korea. The grain-size distribution curves of weathered soil (SW) are shown in Fig.
데이터처리
In order to evaluate the effect of wetting band depth and magnitude of the matric suction on the stability of slopes in unsaturated soils, three sets of analysis were conducted using the limit equilibrium based on SLOPE/W program (GEO-SLOPE, 2004). Three infinite slopes — inclined at 26°, 33°, 45° — were considered, and strength parameter, such as (矿 and c of each mixed soil was fixed as properties of each mixed soil to identify the relation to the only wetting band depth due to rainfall in a slope (Fig.
성능/효과
(2) The increasing rate of the wetting band depth was decreased as the fines contents in the mixtures and the relative densities were increased. These results come from the decrease of the coefficient of permeability and the increase of the soil suction.
(3) According to the stability analysis result of the unsaturated soil slopes through the SLOPE/W, it is found that the transition from the wetting band depth to the variation of strength parameters which affect the stability of unsaturated soil slopes appears to occur around 10 〜15% of clay contents in the mixtures.
6S the volumetric water content decrement was decreased as the fines content of each soil mixture was increased. And the volumetric water content had critical differences between SW100% and other soil mixture (SW95%+CH5%, SW90%+CH10%, SW85%+CH15%, SW80%+CH20%). However, there were no notable distinctions on soils that were mixed with some fines.
densities were increased. And the volumetric water content had critical distinction between SW100% and other soil mixtures (SW95%+CH5%, SW90%+ CH10%, SW85%+CH15%, SW80%+CH20%).
If the factor of safety was only affected by the magnitude of wetting band depth, it must increase as the fines content was increased in soil mixtures. However, the factor of the safety decreased by a certain point - slope containing 20% fines content inclined to 26° and 33° hardened 70% relative density came to have 15% fines content inclined to 45° and hardened 70% relative density (Fig. 12), and any slope contained 15% fines content and hardened 90% relative density (Fig. 13). This means that the effect of the wetting band depth on slope stability is somewhat limited to fine content in soil mixtures.
참고문헌 (17)
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