투수 및 암반거동을 고려한 터널 라이닝의 거동 분석

공정식(Kong Jung-Sik),최준우(Choi Joon-Woo),남석우(Nam Seok-Woo),이인모(Lee In-Mo) 대한토목학회 2006 대한토목학회논문집 C Vol.26 No.5

시공후 터널의 거동에 영향을 주는 대표적인 인지들로 시간에 따른 투수상태와 지반의 장기거동을 들 수 있다. 본 연구에서는 이러한 인지들과 관련된 터널거동을 분석하기 위한 수치해석모델을 개발하고 터널이 겪을 수 있는 다양한 시공 후 하중 조건에 대하여 수치해석을 수행하였다. 터널 변상에 대한 영향인자와 터널거동의 메카니즘을 파악하기 위해 가능한 모든 변상 발생 시나리오를 구성하였으며, 부직포의 투수계수, 수위상승, 장기적인 이완하중과 과발파로 인한 손상 등 터널의 시공 후 장기 변상에 관련된 인자들이 조사되었다. 시공 후 터널 변상 발생 시나리오는 터널형식과 그에 따른 하중 메카니즘에 따라 크게 두 가지로 구분할 수 있음을 알 수 있었다. 토사터널에 대해서는 투수상태와 관련된 거동이 주요 변상의 원인으로 분석되었으며 배수재의 투수계수 저하와 수위상승에 의한 영향에 대해 분석하였다. 암반 터널에서는 암반의 점소성거동을 분석하였고 암반의 이완과 크립에 의한 장기적인 이완하중의 영향에 대해 연구하였다. After construction, time-variant seepage and long-term underground motion are representative factors to understand the abnormal behavior of tunnels. In this study, numerical models have been developed to analyze the behavior of tunnels associated with seepage and long-term underground motion. Possible scenarios have been investigated to establish causes-and-results mechanisms. Various parameters such as permeability of tunnel filter, seepage condition, water table, long-term rock mass load, size of damaged zone due to excessive blasting have been investigated. These are divided into two sub-parts depending on the tunnel type and major loading mechanisms depending on the types. For the soft ground tunnels, the behavior associated with seepage conditions has been studied and the effect of permeability change in tunnel-filter and the effect of water-table change which are seldom measurable are investigated in detail. For the rock mass tunnels, tunnel behavior associated with the visco-plastic behavior of rock mass has been studied and the long-tenn rock mass loads as a result of relaxation and creep have been considered.

Experimental Study on the Permeability Characteristics of Sandstone in Different Chemical Solutions

Yao Huayan,Zhang Zhenhua,Li Dezhong 대한토목학회 2018 KSCE JOURNAL OF CIVIL ENGINEERING Vol.22 No.9

Groundwater seepage is one of the important factors which affect the physical and mechanical properties of soft rock. In this study, the permeability evolution of sandstone was investigated using water solution seepage tests with different pH values. The results show that the chemical nature of the solutions has a great influence on the evolution of the permeability coefficients of sandstone specimens. Over time, it was determined that the permeability coefficient under the solution with PH = 2 was significantly greater than those under the PH = 7 and PH = 12 solutions used in this study. During the infiltrations, the ions of H+ and OH- which were involved in the water-rock interaction made the pH value of the solution change with different degrees. After the seepage, the ions in the solutions changed significantly. The ion concentrations seeping from sandstone specimen in the acidic solution, such as Ca2+, Mg2+, Fe3+ (Fe2+), Al3+ and K+, were found to be much greater than in the neutral and alkaline solutions. However, the ion concentrations seeping from sandstone specimen in the neutral solution displayed little differences from those in the alkaline solution. The concentration of the Si ion in the alkaline solution was much higher than those of the acid and neutral solutions, and the concentration of the acid solution was slightly higher than that of the neutral solution. The changes in the ion concentration in the osmotic solution reflected that there had been different forms of chemical reactions between the minerals of the sandstone and the solutions. The seepage pressures also had some effects on the permeability coefficients, pH values, and concentrations of ions in the solutions. After the seepage tests, the rock microstructures were observed by the means of a Scanning Electron Microscope (SEM). The results show that some new holes have been formed in the sandstone specimen due to the seepage, especially in the sample with the acid solution. The internal structural changes of the sandstone are found to be the main reasons for the changes in the permeability coefficients.

하천제방 직선부 및 만곡부의 침윤선 변화 분석

이승호,강휴택 한국지반공학회 2009 한국지반공학회논문집 Vol.25 No.9

In this study we analyzed the seepage characteristics of meandering section of rivers commonly seen in domestic terrain. The seepage analysis is designed to be more realistic by considering a tangent and meandering section of levee. The levee was idealized to reflect the relevant characteristics by considering the curved angle of 90 degrees and 130 degrees in the spatial frequencies, water elevation conditions, and hydraulic conductivities. Seepage analysis becomes more detailed and precise with the seepage curve shape which is interpreted to indicate the flow of three-dimensional numerical analysis program using VisualFEA. As a result of the analysis, it is shown that the water level in the straight levee was constant, regardless of hydraulic conductivities, and the total head in the meandering section was increased by the overlapping of seepage. Consequently, it is found that the total head was increased more significantly in the case of 90 degrees curved levees than 130 degrees, and the total head showed similar characteristics in the straight levee.

정규화된 수두손실률에 의한 방조제 구간별 차수상태 평가

임성훈,허건,Eam, Sung Hoon,Heo, Gun 한국농공학회 2014 한국농공학회논문집 Vol.56 No.6

In this study the process of normalizing hydraulic head loss rate was developed for the purpose of estimation of seepage blocking state at each seepage segment in sea dike embankment. Pore water pressure sensors were installed with some interval along seepage path, then the hydraulic head loss rate at each segment between pore water pressure sensors was calculated, and then the calculated hydraulic head loss rate was normalized based on seepage path length. The comparison of normalized hydraulic head loss rates showed that the cross section of sea dike embankment was homogeneous approximately and the width of cross section was long enough to blocking tide water.

Stability Analysis of Baishuihe Landslide Considering Spatial Variability of Saturated Hydraulic Conductivity

( Yang Xue ),( Yiping Wu ) 대한지질공학회 2019 대한지질공학회 학술발표회논문집 Vol.2019 No.2

Spatial variability of saturated hydraulic conductivity (Ks) in accumulative landslide exists and affects the saturated-unsaturated seepage characteristic. It is important to carry out the stability analysis of landslide considering spatial variability of Ks. Spatial distribution characteristics of Ks in Baishuihe landslide obtained by the surface nuclear magnetic resonance technology (SNMR) are investigated using the geostatistics. The non-stationary random field of Ks and the non-intrusive stochastic finite element process are established. On this basis, numerical simulations of the uncertain model and deterministic model under reservoir water fluctuation are carried out to study their seepage-deformation and stability characteristics. The results show that: compared with the deterministic model, the change of the pore pressure of the uncertain model is more lagged and more obvious during the reservoir water filling period; the overall displacement of the uncertain model is larger than the deterministic model under reservoir water drawdown; with the increase of reservoir water deceleration, the pore pressure hysteresis of uncertain model is more obvious, where displacement deformation is larger and stability is smaller. Stability analysis shows that ignoring the spatial variability of Ks will overestimate the stability of the landslide.

지속적 수위변동 및 월류에 따른 저수지 제체의 거동 연구

이충원(Chungwon Lee),맹영수(Youngsu Maeng),김용성(Yongseong Kim) 한국지반환경공학회 2014 한국지반환경공학회논문집 Vol.15 No.6

본 연구에서는 현장응력상태 및 수위변동을 재현한 원심모형실험을 통하여 속도변화를 고려한 지속적 수위승강에 따른 제체의 거동을 검토하였으며, 기후변화에 따른 기습적 폭우 상황을 상정한 월류 시 제체의 파괴거동을 모사하였다. 실험 결과, 제체 내의 간극수압 및 변위는 수위상승 및 하강속도에 비례하여 증감하며, 제정부 및 제체 하류측 사면부의 변위증분은 수위승강속도에 대하여 독립적임을 알 수 있었다. 또한 반복적이고 지속적인 수위변동은 변위의 누적을 통해 제체의 변형을 진행시키는 요인이 되며, 월류에 의해 저수지 제체의 안정성이 급격히 저하됨을 확인하였다. 따라서 호우 등으로 수위가 급상승하는 경우 간극수압, 변위 등을 실시간으로 감시하고, 이상 발생 시 수문개방 등을 통해 저수지의 수위를 조절하는 조치를 강구할 필요가 있다. In this study, the behavior of fill dam with continuous water level change considering velocity changes via centrifugal model test was investigated. In addition, the collapse of fill dam due to the overflow was also experimentally simulated. The experimental results demonstrate that the pore water pressures and displacements vary in proportion to the water-level-change velocity, and the displacement increment is independent to the water-level-change velocity. Also, it is confirmed that the continuous water level change induces to the progress of fill-dam deformation due to displacement accumulation and the fill-dam stability dramatically degrades owing to the overflow. Hence, the real-time monitoring of pore water pressures and displacements of fill dam, and the control of water level in heavy rain through the countermeasure such as opening sluice gates are needed to ensure the stability of fill dam.

수위상승속도에 따른 저수지 제체의 거동특성 연구

이충원,장동수,박성용,김용성,Lee,Chung-Won,Chang,Dong-Su,Park,Sung-Yong,Kim,Yong-Seong 한국방재학회 2014 한국방재학회논문집 Vol.14 No.1

저수지 제체의 안정성 연구에 있어 원심모형실험은 널리 이용되어 왔으나, 현재까지 수위상승속도를 고려한 제체의 안정성 연구에 대한 사례는 미진한 실정이다. 따라서, 본 연구에서는 수위상승속도에 따른 저수지 제체의 거동을 고찰하기 위하여 현장응력상태 및 수위상승과정을 재현한 원심모형실험과 침투-변형의 연성(coupling)을 고려한 수치해석을 수행하였다. 그 결과, 수위상승속도의 증가는 제체의 변위 및 간극수압의 급격한 증가요인이 되어 제체의 안정성을 저하시킬 가능성이 있음을 확인하였다. 따라서, 호우 등에 의해 급격히 수위가 증가하는 경우에는 제체의 변위와 간극수압 등의 실시간 모니터링을 통하여 저수지 제체의 안정성이 유지되도록 하여야 한다. Centrifugal model testing has been widely used to study the stability of levees. However, there have been a limited number of physical studies on levees considering velocity of increasing water levels. In this study, to investigate the behavior of reservoir levees with different velocities of increasing water levels, centrifugal model tests and seepage-deformation coupled analyses were conducted. The results from the centrifugal model test and the numerical analysis demonstrate that increasing water velocities induces dramatic increases in the displacement and pore water pressure, so that the levee stability is possibly degraded. Hence, real-time monitoring of the displacement and the pore water pressure of a levee is important to ensure the levee stability.

노후화된 균일형 저수지 제체의 월류모형실험과 3차원 침투특성

이영학,이태호,이달원 한국농공학회 2019 한국농공학회논문집 Vol.61 No.2

In this study, an overtopping model experiments and three dimensional seepage characteristics at the deteriorated homogeneous reservoirs wereperformed to investigate the behavior of failure for embankment and spillway transitional zone due to overtopping. The failure pattern, pore waterpressure, earth pressure and settlement by overtopping were compared and analyzed. The pattern of the failure by overtopping was gradually enlargedtowards reservoirs crest from the spillway transition zone at initial stage. In the rapid stage and peak stage, the width and depth of failure graduallyincreased, and the pattern of the failure appeared irregular and several direction of the erosion. In the early stage, the pore water pressure at spillwaytransitional zone was more affected as its variation and failure width increased. In the peak stage, the pore water pressure was significantly increasedin all locations due to the influence of seepage. The earth pressure increased gradually according to overtopping stage. The pore pressure by thenumerical analysis was larger than the experimental value, and the analysis was more likely to increase steadily without any apparent variation. Thehorizontal and vertical displacements were the largest at the toe of slope and at the top of the dam crest, respectively. The results of this displacementdistribution can be applied as a basis for determining the position of reinforcement at the downstream slope and the crest. The collapse in theovertopping stage began with erosion of the most vulnerable parts of the dam crest, and the embankment was completely collapsed as the overtoppingstage increased.

Sand Flow Characteristics Induced by Static and Dynamic Seepage Pressure under Constant Perimeter Pressure Conditions

Xingxin Chen,Wencheng Shi,Xinran Zhang,Liqun Guo 대한토목학회 2024 KSCE Journal of Civil Engineering Vol.28 No.8

During the construction of coastal projects, the formation of seepage channels within the soil body, induced by fluctuating water pressure, can result in consequential damage to the soil structure, ultimately culminating in sudden water gushing sand disasters. In order to investigate the impact of static and dynamic seepage pressures on sand flow and water flow conditions, an intelligent water pressure loading device was devised to consistently apply a confining pressure of 60 kPa to the specimens. The three static seepage pressures and nine fluctuating seepage pressures were applied to the specimens under the condition of constant confining pressure to study the effect of static and dynamic seepage pressures on sand flow and flow conditions. The outcomes of the experiments revealed that, when the base water pressure of the dynamic seepage pressure is the same as the static seepage pressure, the cumulative seepage volume and permeation velocity of the dynamic seepage pressure are always larger than that of the static seepage pressure. Moreover, higher static pressures increase forces on particles, enhancing permeation velocity, and cumulative seepage volume. Notably, longer periods of pressure fluctuations in dynamic seepage pressures and lower basic water pressures weaken the effect of dynamic seepage pressures.

Landslide Analysis of River Bank Affected by Water Level Fluctuation Ⅰ

Kim You-Seong(김유성),Wang Yu-Mei(왕유메이) 한국지반신소재학회 2010 한국지반신소재학회 논문집 Vol.9 No.3

저수지의 수위변화는 저수지 주변 강기슭 사면파괴의 주요 요인이다. 중국의 삼협댐 저수위는 홍수량 조절을 위해 145m와 175m사이에서 변화한다. 삼협댐 저수위의 정상적 운영상태에서 저수위 변동속도는 0.67m~3.0m의 범위에 있다. 마지아고 사면은 자시강의 2.1㎞ 상류 좌측기슭에 위치한다. 자시강은 삼협지역내에 있는 양츠강의 지류이다. 2003년 저수위가 95m에서 135m로 상승한 직후, 마지아고 사면의 후면부에서 길이 20m, 폭 3~10의 균열이 발생하였다. 지금은 균열 보수 후 특별한 징후는 보이지 않고는 있으나, 이 큰 균열은 마지아고 사면의 산사태 가능성을 암시하고 있었다. 이 연구에서는 저수위 변화와 관련하여 사면내에서 간극수압의 변화를 모의하기 위해 불포화 및 포화 침투해석이 수행되었다. 얻어진 간극수압은 저수위에 따른 안전율 변화를 평가하기 위해 사용되었다. 연구결과 침윤선은 저수위 변화보다 상당히 지연된 반응을 보였고, 저수위의 상승-하강과정에서 침윤선은 각각 요면과 철면의 형상을 나타내었다. 또한 저수위의 변동은 사면의 전면부에만 영향을 미치고 있었고 후면부에는 영향을 미치지 않았다. The change of water level in reservoirs is an important factor causing failure of bank slopes, i.e. landslide. The water level of Three Gorges reservoir in China fluctuate between 145 m and 175 m, as a matter of flood control. During its normal operational state, the rate of water level fluctuation is supposed to range from 0.67 m/d to 3.0 m/d. Majiagou slope is located on the left bank of Zhaxi River, 2.1 ㎞ up from the outlet. Zhaxi River is a tributary of the Yangtze River within the Three Gorges area, of which the water level changes with the reservoir. At the back of Majiagou slope, a 20 m long and 3~10 cm wide fissure developed just after the reservoir water level rose from 95 m to 135 m in 2003. This big fissure was a full suggestion of potential failure of this slope. In this study, unsaturated-saturated seepage analyses were carried out to simulate the change of pore-water pressures in the bank slope subjected to the reservoir water level change. The obtained pore-water pressures were then used to evaluate the change in factor of safety (FS) with reservoir water level. It was found that the phreatic line showed a delayed response with respect to the change of the reservoir water level, because the seepage through soil layer was generally slower than water flows itself. During the rising and drawdown process, the phreatic lines take the shapes of concave and convex, respectively. And the fluctuation of reservoir water level just affected the front part of the bank slope, but had little influence on the back of the slope.