Experimental and Theoretical Study of Seepage Models under Confining Pressure for A Single Rock Fracture

Peng Zhou,Haichun Ma,Jingping Wang,Jiazhong Qian 대한토목학회 2024 KSCE Journal of Civil Engineering Vol.28 No.5

The engineering water inrush events were affected by the hydraulic characteristics of the fractures. In order to quantitatively study the seepage characteristics of the fractures, the experimental analysis of artificial fracture of shale was carried out under different confining pressure (22 MPa − 38 MPa) to explore the influence of confining pressure on seepage characteristics. Three theoretical constitutive formulas to describe the characteristics of seepage were proposed based on cubic law and fracture constitutive equation (Bandis model, Rong model, Sun model), and these theoretical constitutive formulas all had good fitting results to experiment results which indicated that the derived formulas are feasible. The parameters for the three models were compared, among which the Rong model was more suitable to describe the connection between (Q) and (Pc). Rong model and Sun model were highly descriptive to the relationship between (Pc) and (Ps). The formulas that based on three theoretical models can provide quantitative calculation for the influence of in-situ stress change on the seepage of fractures in engineering practice.

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.

Seepage characteristics of the leaching solution during in situ leaching of uranium

Zeng Sheng,Song Jiayin,Sun Bing,Wang Fulin,Ye Wenhao,Shen Yuan,Li Hao 한국원자력학회 2023 Nuclear Engineering and Technology Vol.55 No.2

Investigating the seepage characteristics of the leaching solution in the ore-bearing layer during the in situ leaching process can be useful for designing the process parameters for the uranium mining well.We prepared leaching solutions of four different viscosities and conducted experiments using a selfdeveloped multifunctional uranium ore seepage test device. The effects of different viscosities of leaching solutions on the seepage characteristics of uranium-bearing sandstones were examined using seepage mechanics, physicochemical seepage theory, and dissolution erosion mechanism. Results indicated that while the seepage characteristics of various viscosities of leaching solutions were the same in rock samples with similar internal pore architectures, there were regular differences between the saturated and the unsaturated stages. In addition, the time required for the specimen to reach saturation varied with the viscosity of the leaching solution. The higher the viscosity of the solution, the slower the seepage flow from the unsaturated stage to the saturated stage. Furthermore, during the saturation stage, the seepage pressure of a leaching solution with a high viscosity was greater than that of a leaching solution with a low viscosity. However, the permeability coefficient of the high viscosity leaching solution was less than that of a low viscosity leaching solution.

성토제 하부에 매설된 사석층의 침투특성

이행우,장병욱 한국지반공학회 2005 한국지반공학회논문집 Vol.21 No.8

Rocks are dumped to soft marine ground in order to improve trafficability and construction conditions in the tideland reclamation construction sites. Though this rock layer under earth fill has caused in a serious seepage problems after construction, seepage behaviors of this embankment structure is not correctly investigated. Water flow through rock layers is, in general, known as Non-Darcy’s flow. However, the embedded rock layer under earth fill is not known whether its flow is governed by Darcy’s or Non-Darcy’s law. Therefore, a numerical analysis, laboratory model test and filed investigations were performed for analyzing the those seepage characteristics in this research. Results show that there is significance of 95% of confidence between observed heads and seepage rates, and the calculated ones by SAMTLE which is developed under the assumption that the water flows through the two-layer system obey the Darcy’s flow. And after operating the hydraulic gradient(i) of 0.10~0.55 upon laboratory model, these seepage characteristics of the embedded rock layer show that Reynolds Numbers are less than 10 and the relationship between these velocities of rock layer(v) and hydraulic gradients(i) is linearly proportional with more than 0.79 of the coefficient of correlation (R2). And the Reynolds Number of the velocity calculated by the relation of in the embedded rock layer of ○○ sea dike is 1~6. It shows also laminar flow. Based on these results, it is concluded that the seepage characteristics of embedded rock layer under earth fill can be laminar and Darcy’s flow.

필터간격을 고려한 농업용저수지 제체의 침투특성

이영학,이달원 한국농공학회 2018 한국농공학회논문집 Vol.60 No.1

This study analyzed pore water pressure, seepage and leakage quantity, height of seepage and critical hydraulic gradient in order to suggest the seepage characteristics of agricultural reservoir embankment considering filter interval. The seepage characteristics of a deteriorated reservoir embankments were conducted according to the horizontal filter intervals range using three- dimensional finite element analysis. The wider the horizontal filter interval, the higher the pore water pressure increased, and the pore water pressure ratio in the center of the core has a greater effect than the base part. The seepage and leakage quantity appeared largely in the two-dimensional analysis conditions (case 1), where the filter was constructed totally in the longitudinal direction of the embankment, the wider the horizontal filter interval was gradually reduced. The reasonable filter intervals to yield efficient seepage characteristics were within 30 m for the pore water pressure of the core and the height of the seepage line. The stability of the filter installation was able to evaluate the stability of the piping by the critical hydraulic gradient method. The deteriorated reservoir with no filters or decreased functionality can significantly reduce the possibility of piping by simply installing a filter on the downstream slope. In the future, the deteriorated reservoir embankment should be checked for the reservoir remodeling because the core and filter functions have been lost or decreased significantly. In the case of a new installation, the seepage characteristic behavior due to the core and filter changes should be applied to the field after obtaining a reasonable horizontal filter interval that satisfies the safety factor by a three-dimensional analysis.

월류방지 구조물 설치에 따른 농업용 저수지의 침투특성

류정현(Ryu, Junghyun),이영학(Lee, Younghak),윤보라(Yoon, Bora),이달원(Lee, Dalwon) 한국방재학회 2022 한국방재학회논문집 Vol.22 No.2

본 연구에서는 노후화된 농업용저수지에 이상강우에 의한 월류를 효과적으로 방지할 수 있는 월류방지 구조물을 설치하고, 침투특성을 모형실험과 수치해석을 통해 비교분석하여 현장실용화 방안을 마련하고자 하였다. 실험 조건은 댐마루에 Gabion 옹벽, Geomembrane, Core가 복합적으로 설계된 3가지 형식의 월류방지 구조물인 계단형 Gabion 옹벽, 수직형 Gabion 옹벽, Parapet을 설치하고 홍수위부터 월류수위까지 수위를 상승시키며 관측하였다. 실험결과, 변형 및 변위결과는 전도와 파괴 등의 결함문제가 발생하지 않았고 매우 미소한 수평변위와 수직변위를 나타내어 효과적으로 월류를 방지하는 것으로 나타났다. 침윤선과 공극수압 분포 결과로부터 침투수는 상류사면에서부터 필터를 통해 Toe-drain으로 원활하게 배수되는 것으로 나타났고, 댐마루 상부에 침투수가 집중되면 하류사면 상부로 누수를 발생시켜 월류방지 구조물 하부의 안정성에 영향을 미칠 수 있는 것으로 평가되었다. 동수경사 분포는 하류사면선에서 모든 형식이 안정한 것으로 평가되었고, 잠재적인 취약부가 될 수 있는 하류사면 상부는 누수의 영향을 받을 수 있어 Geomembrane의 시공 시 섬세한 시공관리가 필요한 것으로 나타났다. 전체적으로, 적용된 3개의 월류방지 구조물 중 계단형 Gabion 옹벽은 전도 및 누수 등의 문제가 발생하지 않아 파이핑 안정성을 확보할 수 있기 때문에 다른 형식의 월류방지 구조물보다 우수한 방법으로 평가되었다. In this study, a structure that can effectively prevent overtopping caused by abnormal rainfall was installed in a deteriorative agricultural reservoir, and seepage characteristics were compared and analyzed through model experiments and numerical analysis. The experimental conditions were observed by installing a stepped gabion, vertical gabion, and parapet in combination with a gabion retaining wall, geomembrane, and core on the dam crest. Small horizontal and vertical displacements without defects were found, such as overturning and failure, to effectively prevent overtopping. A comparison of seepage line and pore water pressure results indicates that the seepage water drained smoothly to the toe drain through the filter from the upstream slope. It was perceived that the concentration of seepage water on the upper part of the dam crest might cause leakage to the upper part of the downstream slope and affect the stability of the overtopping prevention structures. The distribution of the hydraulic gradient was found to be stable in all cases on the downstream slope. The upper part of the downstream slope could be vulnerable to leakage, so careful management is required when constructing the geomembrane. Overall, among the three overtopping prevention structures applied, a stepped gabion retaining wall did not cause such problems as overturning and leakage. Therefore, it is considered better than the other types of overtopping prevention structure.

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.

비탈끝 배수공이 설치된 균질제방의 침투특성에 대한 해석적 연구

이승현(Seung-Hyun Lee),김응석(Eung-Seok Kim) 한국산학기술학회 2022 한국산학기술학회논문지 Vol.23 No.4

제방의 파괴원인 중 하나인 침투에 의한 파괴는 국내외적으로 지속적으로 발생되는 문제로서 많은 인적, 물질적 피해를 야기하고 있다. 안전한 제방설계를 위해서는 제방내부로의 침투특성에 대한 이해가 선행되어야 하며 이를 위해 본 연구에서는 비탈끝 배수공이 설치된 균질제방의 침투특성을 살펴보기 위해 제방고와 비탈끝 배수공의 폭을 달리하여 침투해석을 수행하였다. 해석을 위해 가정한 제방단면에 대한 침투해석결과를 통해 침윤선 위쪽의 모관현상 발생영역에서도 물의 흐름이 발생됨을 알 수 있었다. 침윤선 위로의 물의 침투속도는 상당히 느려짐을 알 수 있었는데 이는 침윤선으로부터 연직상향으로 거리가 떨어질수록 흡인력의 증가에 의해 수리전도도가 감소된 결과 때문으로 설명될 수 있다. 비탈끝 배수공의 폭이 커짐에 따라 침윤선으로부터 하류측사면까지의 최소연직거리도 증가하게 되는데 동일한 비탈끝 배수공의 폭에 대하여 제방고가 증가할수록 침윤선으로부터 하류측사면까지의 최소연직거리는 작아짐을 알 수 있었다. 또한, 제방고가 낮을수록 비탈끝 배수공이 없는 경우에 대한 비탈끝 배수공을 적용한 경우의 침투유량의 비는 커짐을 알 수 있었다. 비탈끝 배수공을 적용하지 않은 경우에 있어서 제방바닥으로부터 유출면 상단까지의 높이는 제방고가 커짐에 따라 선형적으로 증가됨을 알 수 있었는데 얻어진 선형회귀분석식을 통해 유출면의 범위를 예측할 수 있을 것으로 기대된다. 본 연구를 통해 비탈끝 배수공의 폭을 결정하기 위해서는 침투해석을 통해 얻은 침윤선으로부터 하류측사면까지의 최소연직거리와 제방재료의 모관상승고 그리고 침투해석을 통해 구한 제체내부로의 침투유량을 종합적으로 고려해야 함을 알 수 있었다. Seepage analysis with varying embankment height and toe drain width was conducted to find the seepage characteristics of a homogeneous embankment controlled by a toe drain. The seepage analysis results for the assumed embankment sections indicate that water flow occurs at a capillary zone above the phreatic line. The minimum vertical distance between the phreatic line and the downstream slope increases as the toe drain width increases. In addition, the minimum vertical distance decreases for certain toe drain width as the embankment height increases. The ratio of water rate computed from the water rates with and without toe drain increases as the embankment height decreases. Results of the analysis also show that the distance between the bottom line of the embankment and the horizontal line which passes through the top point of the seepage face increases linearly as the embankment height increases. Finally, this study concludes that the minimum distance between the phreatic line and the downstream slope, the capillary rise of the embankment material, and the magnitude of water rate through the embankment should be considered to determine the size of the toe drain.

불포화 수리특성에 대한 댐체 침투 거동의 민감도 분석

조성은 한국지반공학회 2005 한국지반공학회논문집 Vol.21 No.3

Seepage analysis through unsaturated zone based on the theory of unsaturated flow is commonly performed to evaluate dam safety. However, the concepts of unsaturated soil behavior have not been transferred into the hands of practicing geotechnical engineers since the problems involving unsaturated soils often have the appearances of being extremely complex. The behavior of dam such as seepage rate and the pore water pressure distribution is different according to the unsaturated hydraulic properties, but nevertheless simply assumed properties have been used due to insufficient data from domestic soils. In this paper, the effect of unsaturated hydraulic properties on the behavior of dam was studied through a series of numerical analyses, and then the results were discussed. It is observed that water table moves at a faster rate, as the values of unsaturated soil parameter a and n increase. The value of m showed opposite trend. The sensitivity calculated using the approximation form showed maximum values near the water table. And the value of n that is related to the slope of soil water characteristic curve gives greatest influence on the change of sensitivity with time.

확률론적 댐 침투거동 해석

조성은 한국지반공학회 2006 한국지반공학회논문집 Vol.22 No.4

Seepage analysis through unsaturated zone based on the theory of unsaturated flow is commonly performed to evaluate dam safety. However, the concepts of unsaturated soil behavior have not been transferred into the hands of practicing geotechnical engineers since the problems involving unsaturated soils often have the appearances of being extremely complex. There is variability and uncertainty associated with the unsaturated hydraulic properties that in turn will lead to variability in predicting unsaturated soil behavior such as seepage rate and the pore water pressure distribution. In this paper, measurements of the soil-water characteristic curve and saturated hydraulic conductivity for the core material of dam were conducted. Then, finite element stochastic analysis was used to capture the effect of unsaturated hydraulic properties on the seepage behavior of dam. It is observed that the amount of seepage increases, as the values of unsaturated soil parameters and increase. The values of and showed opposite trend.