원심모델링을 이용한 보강재 침하형 보강토 옹벽의 거동

안광국(Ahn Kwang-Kuk),김재일(Kim Jae-Il),이처근(Lee Cheo-Keun),정태익(Chung Tae-Ick) 대한토목학회 2007 대한토목학회논문집 C Vol.27 No.2

기존의 블록식 보강토옹벽의 경우 블록과 보강재 사이의 연결을 커넥터 등으로 고정시키는 형식으로 보강재와 블록이 일체로 거동하므로 블록 전면부에 응력집중으로 블록균열이나 보강재의 파단파괴가 발생할 수 있다. 본 연구에서는 보강재의 침하를 허용하는 연결시스템을 적용한 침하형 보강토 옹벽의 거동을 평가하기 위하여 원심모형실험을 수행하였다. 실험결과는 연결부의 침하를 허용하지 않는 일반형 보강토옹벽에 대한 결과와 비교 분석하였다. 실험결과, 침하형 보강토옹벽은 80g의 중력수준에서 완전한 파괴상태에 도달하였으며, 일반형 보강토 옹벽은 69g의 중력수준에서 파괴가 발생하여 침하형 보강토 옹벽의 안정성이 우수한 것으로 나타났다. 또한, 침하형 보강토옹벽의 경우, 69g에서 전면판으로부터 0.15H지점에서 발생한 보강재의 인장력은 일반형 옹벽의 1/6~1/2 정도로 평가되었다. The conventional reinforced earth retaining wall has the connector system to fix the reinforcement and block. However, this system may cause the crack of block and the rupture of reinforcement due to the stress concentration near the face of reinforced earth retaining wall. In this study, the new connector system, which is able to allow the settlement of reinforcement, was applied to analyze the effect of connector system of reinforced earth retaining wall. The centrifugal tests for both the conventional reinforced earth retaining wall and reinforced earth retaining wall driving the settlement of reinforcement were performed to compare the results. As a result, reinforced earth retaining wall driving the settlement of reinforcement reached to the failure at 80g-level. In contrast, the conventional reinforced earth retaining wall was collapsed at 69g-level. It means that reinforced earth retaining wall driving the settlement of reinforcement has the stronger stability than the conventional reinforced earth retaining wall. Also, the tensile force on reinforced earth retaining wall driving the settlement of reinforcement was less at the point of 0.15H about 1/6~1/2 than that of the conventional reinforced earth retaining wall.

치환공법을 적용한 연약지반에 시공된 보강토옹벽의 거동해석

기완서 ( Wan Seo Ki ),주승완 ( Seung Wan Joo ),김선학 ( Sun Hak Kim ) 대한지질공학회 2007 지질공학 Vol.17 No.4

연약지반에 보강토옹벽을 시공 시 거동에 영향을 주는 인자로 기본적인 물성뿐만 아니라 보강토옹벽에 의한 하중증가와 압밀기간, 간극수압 등의 영향을 받는 것으로 보고되고 있다. 본 연구에서는 보강토옹벽과 연약지반의 거동해석에 지반해석 프로그램인 SAGE CRISP를 이용하여 수행하였다. 첫 번째로 보강토옹벽의 과도변위를 개선하기 위한 치환공법의 거동 개선 효과를 검토하였으며, 두 번째로 치환공법을 적용 후 보강토옹벽의 배면에 보강재 수직설치간격이 지반의 거동에 미치는 영향을 비교·분석하였다. 마지막으로 치환공법을 적용 시 적정 치환 폭과 깊이를 제안하고자 하였다. 치환공법이 보강토옹벽의 거동 개선에 상당한 효과가 있음을 알 수 있었으며, 보강재 수직설치간격은 옹벽상단의 수평변위개선효과가 있는 것으로 나타났으나 하단의 수평변위와 옹벽배면의 수직변위 개선효과는 미소한 것으로 나타났다. 또한 치환폭의 증가에 따른 수평·수직변 개선효과는 크지 않은 것으로 나타나 치환폭의 증가는 불필요함을 알 수 있었으며, 적정 치환깊이는 연약층의 두께에 대한 옹벽높이의 비(H/T)에 따라 옹벽높이에 대한 치환깊이의 비(D/H)로 제안하였다. It is reported that factors affecting the behavior of reinforced earth retaining walls built on soft ground are not only basic physical properties but also the increase of load by the reinforced earth retaining walls, consolidation period, pore water pressure, etc. This study analyzed the behavior of reinforced earth retaining walls and soft ground using SAGE CRISP, a ground analysis program. First, we examined the effect of the replacement method, which was to prevent the excessive displacement of reinforced earth retaining walls, in improving the behavior of the walls. Second, we compared and analyzed how the behavior of ground is affected by the vertical interval of stiffeners on the back of reinforced earth retaining walls after the application of the replacement method. Lastly, we proposed the optimal replacement width and depth in the application of the replacement method. The results of this study proved that the replacement method is considerably effective in improving the behavior of reinforced earth retaining walls. In addition, the vertical interval of stiffeners on the back of reinforced earth retaining walls appeared effective in improving the horizontal displacement of the top of retaining walls but not much effective in improving the vertical displacement of the back of retaining walls. In addition, improvement in horizontal-vertical displacement resulting from the increase in replacement width was not significant and this suggests that the increase of replacement width is not necessary. With regard to an adequate replacement depth, we proposed the ratio of replacement depth to the height of retaining walls(D/H) according to the ratio of the thickness of the soft layer to the height of retaining walls(H/T).

동적원심모형실험을 이용한 지진 시 역T형 옹벽의 관성력 영향 분석 사례 연구

조성배,하정곤,추연욱,김동수 한국지반공학회 2013 한국지반공학회논문집 Vol.29 No.4

Mononobe-Okabe (M-O) theory is widely used for evaluating seismic earth pressure of retaining wall. It was originally developed for gravity walls, which have rigid behavior, retaining cohesionless backfill materials. However, it is used for cantilever retaining wall on the various foundation conditions. Considering only inertial force of the soil wedge as a dynamic force in the M-O method, inertial force of the wall does not take into account the effect on the dynamic earth pressure. This paper presents the theoretical background for the calculation of the dynamic earth pressure of retaining wall during earthquakes, and the current research trends are organized. Besides, the discrepancies between real seismic behavior and M-O method for inverted T-shape retaining wall with 5.4m height subjected to earthquake motions were evaluated using dynamic centrifuge test. From previous studies, it was found that application point, distribution of dynamic earth pressure and M-O method are needed to be re-examined. Test results show that real behavior of retaining wall during an earthquake has a different phase between dynamic earth pressure and inertial force of retaining wall. Moreover, when bending moments of retaining wall reach maximum values, the measured earth pressures are lower than static earth pressures and it is considered due to inertial effects of retaining wall.

Evaluation of the seismic earth pressure for inverted T-shape stiff retaining wall in cohesionless soils via dynamic centrifuge

Jo, Seong-Bae,Ha, Jeong-Gon,Lee, Jin-Sun,Kim, Dong-Soo Elsevier 2017 Soil dynamics and earthquake engineering Vol.92 No.-

<P><B>Abstract</B></P> <P>In the design procedure of a retaining wall, the pseudo-static method has been extensively used and the dynamic earth pressure has been calculated based on force equilibrium using the Mononobe–Okabe method that is an extension of the Coulomb's earth pressure theory. According to the Mononobe–Okabe method, the resultant total dynamic thrust would act at a height of 0.33H. The Seed and Whitman method that is a modification of the Mononobe–Okabe method, suggests that the dynamic thrust would be applied at 0.6H above the base. There is no clear empirical basis for the distribution of the dynamic earth pressure, and recent experimental research studies have shown that the dynamic earth pressure has a triangular shape, and that the dynamic thrust is applied at 0.33H above the base. Moreover, pseudo-static methods do not consider the effects of the inertial force of the wall itself on the structural behavior. Two dynamic centrifuge tests were designed and conducted to evaluate the magnitude and distribution of the dynamic earth pressure and the inertial effect of the wall itself on an inverted, T-shape, stiff retaining wall with a dry medium sand backfill. Results from two sets of dynamic centrifuge experiments show that the dynamic earth pressure has a triangular shape for critical states during the earthquake, and that the inertial force of the wall significantly influences the structural moment. Moreover, the deformation pattern, the rigidity of the retaining wall, and the frequency contents of the input motions cause the phase difference between the wall and the soil. Correspondingly, this phase difference influences the dynamic earth pressure.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Distribution of dynamic earth pressures measured by transducers is triangle shape. </LI> <LI> Phase difference depend on deformation, wall rigidity and frequency of input. </LI> <LI> Phase difference between wall and soil influence the dynamic earth pressure. </LI> <LI> Inertial force of the wall should be accounted for when designing cantilever wall. </LI> <LI> Mononobe–Okabe method is an upper bound for coefficient of dynamic earth pressure. </LI> </UL> </P>

Analysis of the Effect of Drainage Related Problems on the Stability of Reinforced Earth Retaining Wall Construction

( Jong Nam Do ),( Nag Young Kim ) 대한지질공학회 2019 대한지질공학회 학술발표회논문집 Vol.2019 No.2

Most of the problems related to drainage during the construction of the reinforced earth retaining wall structure do not occur during construction on the flat ground. However, when the reinforced earth retaining wall is installed in a place where the cut slope or the high embankment, problems related to drainage often occur. Problems associated with drainage on the reinforced earth retaining wall start with the leakage of the front wall part initially. When the front wall is wet by water, leaving it lightly is likely to develop into a big problem later on. If some of the construction is wetted by water, tracing back the flow of water or smoothly draining the already saturated backfill water has a positive effect on the stability of the structure. In some sites, the reinforced earth retaining wall is located at the end of the high embankment, and the surface is drained only in a part of the section, so that no consideration is given to the phenomenon that the upper surface number saturates the filler behind the reinforcing earth retaining wall. When slopes ranging from tens of meters to the top of reinforcing earth retaining wall and the end of embankment are formed, a plan should be prepared to actively drain the surface water. Therefore in this study, an analysis of the case study on the site was presented to solve the problem of drainage of reinforced earth retaining wall.

차량 충돌에 의한 보강토 옹벽의 안정성 평가

안광국(Ahn Kwangkuk),허열(Heo Yol),홍기남(Hong Kinam),안민수(Ahn Minsu) 한국지반환경공학회 2010 한국지반환경공학회논문집 Vol.11 No.6

기존의 보강토 옹벽의 연구는 보강토 옹벽의 내적?외적파괴에 중점이 되어 연구가 이루어져 왔고 외부 충격에 관한 연구는 지진에 관한 것이 전부인 것이 현실이다. 도로의 발달로 인해서 도로 주변의 보강토 옹벽에 차량의 충돌 같은 외부 충격을 받는 경우가 늘어나고 있다. 그래서 본 연구에서는 신뢰도를 인정받고 있는 범용 유한요소 프로그램인 LS-DYNA를 사용하여 도로 주변 보강토 옹벽을 모델링하였고, NCAC에서 제공하는 8톤 중량의 Ford single unit truck을 이용하여 차량속도에 따른 보강토 옹벽의 거동 양상을 분석하였다. 그리고 향후 도로 주변에 시공되어지는 보강토 옹벽의 충돌에 관한 안정성을 확보하기 위해서 하단에 중력식 옹벽을 적용하였고 또한 높이를(0.5m, 1.0m, 1.5m) 변화시켜가면서 수치해석을 수행하여 보강토 옹벽의 거동을 분석하고 보강토 옹벽의 안정성을 확인 하였다. The past studies on reinforced earth retaining wall have been mostly focused on the internal and external failure of reinforced earth retaining wall, and the research for external impact was limited on earthquake. However, the potential external impact such as vehicle collision to reinforced earth retaining wall near the road are increasing with development of roads. Therefore, in this study, the reinforced earth retaining wall was modeled by using LS-DYNA, which is a general purpose finite element program recognized for its reliability. The behavior of reinforced earth retaining wall by vehicle speed was analyzed with Ford single unit truck offered by NCAC (National Crash Analysis Center), which is 8 tons weight. In addition, in order to obtain stability of reinforced earth retaining wall for vehicle collision, the gravity retaining wall was applied at the bottom of reinforced earth retaining wall. With varying the height of retaining wall (0.5m, 1.0m, 1.5m), the numerical study was performed to analyze the stability and behavior of reinforced earth retaining wall.

흙막이 가시설의 거동 분석을 통한 안정성 확보 방안에 관한 연구

김광렬(Kwang-Leyol Kim),김유성(You-Seong Kim),김성수(Seong-Soo Kim) 한국지반신소재학회 2013 한국지반신소재학회 논문집 Vol.12 No.4

최근 해석프로그램과 시공기술의 발달에도 불구하고 많은 흙막이 가시설 공사현장에서 구조물의 붕괴로 인한 경제적·인적 피해가 발생하고 있다. 이번 연구 현장의 지반조사 결과는 원래 설계시 조사결과와 다른 것으로 나타났다. 이러한 경우에 지반조사 결과를 통해 산정된 매개변수는 오류가 있을 가능성이 있고, 그 지반정수를 활용하여 분석한 가시설 구조물의 거동분석도 비합리적임을 추정할 수 있다. 이번 연구에서는 가시설 구조물에 영향을 주는 매개변수에 대한 상관성을 탄소성해석법을 이용하여 분석하였다. 분석방법으로 탄소성해석법에 적용되는 주요 매개변수(점착력, 지반반력계수, 하중조건)를 변화시키고 그 변화로 인한 흙막이 가시설 재료(부재)의 거동을 분석하였다. 그 결과 점착력이 재료의 거동에 가장 큰 영향을 주는 것으로 나타났다. 따라서 흙막이 가시설의 설계에서 지반조사 결과와 실제 지반의 확인과 여러 매개 변수 중에서 점착력의 정확하고 합리적인 산정이 매우 중요함을 알 수 있었다. Recently despite the development of analysis program and construction technologies, collapse at the many earth retaining wall construction site of the structure due to the economic and human damage has occurred. The results of geothechnical investigation studies field, it was found to differ from the results of the original design. There may be errors parameters calculated from the results of ground investigation in such a case. And it can be estimated that it is irrational to behavior analysis of the earth retaining wall were analyzed by utilizing the parameters. And in this study, parameters that affect the earth retaining wall the correlations were analyzed using elasto-plastic method. Analysis method was changed various parameters (cohesion, subgrade reaction coefficient, load condition) applied to the elasto-plastic method. And due to a change in the behavior of earth retaining wall materials were analyzed. As a result, the cohesion greatly affects the behavior of earth retaining wall materials in various parameters. For this reason, the results of the geothechnical investigation, confirmation of the actual ground is very important in the design of the earth retaining wall. And, calculating accurate and reasonable of the cohesion of the various parameters is very important.

뒷굽 길이가 짧은 캔틸레버 옹벽의 Coulomb 토압 산정에 대한 영향 인자 분석

유건선,Yoo, Kun-Sun 한국지반공학회 2017 한국지반공학회논문집 Vol.33 No.11

본 연구에서는 사질토 뒷채움재의 캔틸레버 옹벽에서 뒷굽 끝단 연직면에 작용하는 주동토압을 산정하는 방법을 제안하였다. 캔틸레버 옹벽에서 뒷굽길이에 따른 전단 영역의 변화는 벽체의 벽마찰력, 뒷채움 경사에 따라 뒷굽 끝단 연직면에 작용하는 주동토압에 영향을 준다. 뒷굽길이에 따라 변하는 파괴면각도를 가정하여 토압을 산정하는 한계평형법은 적용하기에 매우 복잡하므로 본 연구에서는 한계해석법을 사용하여 토압을 구하였다. 한계해석법으로 뒷굽길이에 따라 실제 파괴면각도가 고려된 토압을 정확히 산정하고, 이로부터 뒷굽 끝단 연직면에 작용하는 수평토압과 연직토압을 분석하였다. 본 연구결과에 의하면, 뒷굽길이가 짧아짐에 따라 내측 파괴면 경사각은 이론식보다 증가한 반면에 외측 파괴면 경사각은 영향을 받지 않았다. 뒷굽 끝단의 연직면에 작용하는 배면마찰각은 지표면 경사각과 벽면마찰각 사이의 값을 나타내었으며, 주동토압 또한 감소하였다. 최종적으로 상대적인 뒷굽길이와 뒷굽 끝단의 연직면에 작용하는 마찰각(연직토압/수평토압의 비)의 상관관계를 사용함으로써 Coulomb 토압을 간편하게 산정할 수 있도록 하였다. In this study, the calculation method of the active earth pressure acting on the imaginary vertical plane at the end of the heel of the wall is proposed. For cantilever retaining wall, a change of shear zone behind the wall affects the earth pressure in the vertical plane at the end of heel of the wall depending on wall friction and angle of ground slope. It is very complicated to calculate the earth pressure by a limit equilibrium method (LEM) which considers angles of failure planes varying according to the heel length of the wall. So, the limit analysis method (LAM) is used for calculation of earth pressure in this study. Using the LAM, the earth pressures considering the actual slope angles of failure plane are calculated accurately, and then horizontal and vertical earth pressures are obtained from them respectively. This study results show that by decreasing the relative length of the heel, the slope angle of inward failure plane becomes larger than theoretical slope angle but the slope angle of outward failure plane does not change. And also the friction angle on the vertical plane at the end of the heel of the wall is between the ground slope angle and the wall friction angle, thereafter the active earth pressure decreases. Finally, the Coulomb earth pressure can be easily calculated from the relationship between friction angle (the ratio of vertical earth pressure to horizontal earth pressure) and relative length of the heel (the ratio of heel length to wall height).

염해로 인한 교대부 보강토옹벽 손상 원인 분석 연구

도종남(Jong-Nam Do),김낙영(Nag-Young Kim),조남훈(Nam-Hun Cho),유광호(Kwang-Ho You) 한국지반환경공학회 2018 한국지반환경공학회논문집 Vol.19 No.12

보강토옹벽에 발생되는 손상은 전면벽체부, 기초부, 배수로, 상부사면으로 구분하여 발생되고 있다. 보강토옹벽의 손상은 주로 배수문제로 인한 손상이 현장에서 많이 발생되는데, 이 중 제설염에 의한 손상이 최근에 사례화 되고 있는 실정이다. 최근 이상기후로 인해 겨울철에 사용되어지는 제설염의 양이 점점 늘어나고 있다. 이 제설염은 콘크리트 구조물을 열화시키는데, 여기서 보강토옹벽도 예외는 아니다. 배수통로를 통해 뒤채움부로 유입된 염해 성분이 보강토옹벽의 전면벽체를 열화시키는 사례가 최근 발생되고 있다. 따라서, 본 연구에서는 교량의 교대부에 시공된 보강토옹벽의 손상원인을 분석하고, 이에 대한 대책에 대한 분석연구를 수행하였다. 연구 결과, 교량 교대부의 신축이음장치나 상부 구조에서 집수된 배수계통을 통해 유입된 염해 성분이 보강토옹벽 뒤채움부로 유입되어 손상이 발생되는 것으로 나타났다. 따라서, 배수체계를 개선하고 전면벽체의 강성을 회복하는 방안을 제시하였다. The damages to the reinforced earth retaining wall are divided into the front wall, foundation, drainage and upper slope. Damage of reinforced earth retaining wall is mainly caused by damage caused by drainage problem in the field. Recently, damage caused by snow removal materials have been occurred. Recently, the amount of snow removal materials used in winter is increasing due to abnormal weather. This chlorides degrades the concrete structure, where the reinforced earth retaining wall was no exception. There has recently been a case in which the front wall of the reinforced earth retaining wall deteriorates due to the chlorides introduced into the back filling portion through the drainage passage. Therefore, in this study, the cause of damages of reinforced earth retaining wall constructed in bridge abutment was analyzed, and an analytical study was conducted on the countermeasure. As a result, it was found that chlorides, which was introduced through the drainage system in the expansion joint of the bridge shift part or the upper structure, is infiltrated into the back part of the reinforced earth retaining wall and damaged. Therefore, it is suggested to improve the drainage system and restored the stiffness of the front wall.

Preventive Maintenance Technique of Reinforced Earth Retaining Wall Structures

Jong-nam Do,MoonS Nam 한국도로학회 2018 한국도로학회 학술대회 발표논문 초록집 Vol.2018 No.05

The reinforced retaining wall was introduced in the late 1980s and has been actively used since the 1990s in Korea 's expressway construction. At the beginning of the introduction, proper stiffeners and backfill materials were used and compaction management was thoroughly carried out, which was recognized as an economical and excellent workability method. However, the current understanding of reinforced earth retaining walls about 30 years old is a negative image such as inadequate reinforcement materials, backfill materials, insufficient compaction, and insufficient drainage system. In this way, the reinforced earth retaining walls that have been constructed in the midst of the negative perception are about 1,000 at the expressway site, and about 1000 will be completed in a few years and about 2,000 will be used. Most of the problems of reinforced earth retaining wall were found during maintenance, and countermeasures are suggested by tracing back to what problems were observed in the design and construction of the observed phenomena. The retaining walls to be installed in future maintenance should be minimized in designing and constructing to prevent problems. It is estimated that such a problem can be solved by changing the recognition. Therefore, in this study, damage cases of reinforcement retaining wall which is frequently occurred in the expressway of Korea were analyzed to derive the preventive maintenance method of reinforced earth retaining walls. Then, the problems and countermeasures were analyzed for each type of damage.