• Geomechanics and Engineering
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• v.15 no.1
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• pp.677-686
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• 2018

Aimed at serious casing damage problem during the process of oilfield development by injecting water, based on seepage mechanics, fluid mechanics and the theory of rock mechanics, the multi-physics coupling theory was also taken into account, the mathematical model for production of petroleum with water flooding was established, and the method to solve the coupling model was presented by combination of Abaqus and Eclipse software. The Q9G3 block in Jibei oilfield was taken for instance, the well log data and geological survey data were employed to build the numerical model of Q9G3 block, the method established above was applied to simulate the evolution of seepage and stress. The production data was imported into the model to conduct the history match work of the model, and the fitting accuracy of the model was quite good. The main mechanism of casing damage of the block was analyzed, and some wells with probable casing damage problem were pointed out, the displacement of the well wall matched very well with testing data of the filed. Finally, according to the simulation results, some useful measures for preventing casing damage in Jibei oilfield was proposed.

• Nuclear Engineering and Technology
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• v.55 no.2
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• pp.566-574
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• 2023

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 self-developed 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.

• Geomechanics and Engineering
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• v.25 no.2
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• pp.159-170
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• 2021

Particle size of tailings in different areas of dams varies due to sedimentation and separation. Saturated hydraulic conductivity of high-stacked talings materials are seriously affected by void ratio and particle breakage. Conjoined consolidation permeability tests were carried out using a self-developed high-stress permeability and consolidation apparatus. The hydraulic conductivity decreases nonlinearly with the increase of consolidation pressure. The seepage pattern of coarse-particle tailings is channel flow, and the seepage pattern of fine-particle tailings is scattered flow. The change rate of hydraulic conductivity of tailings with different particle sizes under high consolidation pressure tends to be identical. A hydraulic conductivity hysteresis is found in coarse-particle tailings. The hydraulic conductivity hysteresis is more obvious when the water head is lower. A new hydraulic conductivity-void ratio equation was derived by introducing the concept of effective void ratio and breakage index. The equation integrated the hydraulic conductivity equation with different particle sizes over a wide range of consolidation pressures.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2009.11a
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• pp.495-496
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• 2009

• Nuclear Engineering and Technology
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• v.56 no.4
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• pp.1357-1371
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• 2024

To investigate the influence of different burial conditions on the seepage characteristics of loose sandstone in the leaching mining of sandstone uranium ore, this study applied different ground pressures and water pressures to rock samples at different burial depths to alter the rock's seepage characteristics. The permeability, pore distribution, and particle distribution characteristic parameters were determined, and the results showed that at the same burial depth, ground pressure had a greater effect on the reduction in permeability than water pressure. The patterns and mechanisms are as follows: under the influence of ground pressure, increasing the burial depth compresses the pores in the rock samples, decreases the proportion of effective permeable pores, and causes particle fragmentation, which blocks pore channels, resulting in a decrease in permeability. Under the influence of water pressure, increasing the burial depth expands the pores but also causes hard clay particles to decompose and block pore channels. As the burial depth increases, the particles eventually decompose completely, and the permeability initially decreases and then increases. In this experiment, the relationships between permeability and the proportion of pores larger than 0.15 ㎛ and the proportion of particles smaller than 59 ㎛ were found to be the most significant.

• Tunnel and Underground Space
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• v.18 no.5
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• pp.366-374
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• 2008

Tunnelling under water table induces many geotechnical problems because of groundwater. In subsea tunneling, reduction of face stability can induce flooding in the vicinity of a fracture zone characterized by high permeability and high water pressure. In this study, the effects of high water pressure on the stability of a tunnel face in a limited zone with high permeability(hazardous zone) are analyzed. On the basis of the 'advance core' concept, the seepage force acting on a hypothetical cylinder ahead of a tunnel face is modeled. This study focuses on the hydraulic behavior of the ground ahead of the tunnel face by three-dimensional steady-state seepage analyses. The impact of the hazardous zone on the seepage force and stability of the tunnel face are simulated and analyzed. In light of the analysis results, it is estimated that the distance from the tunnel face to the exterior boundary limit, which the seepage force significantly affects the stability of the tunnel face, of a hypothetical cylinder is approximately 5 times the tunnel radii. Despite the restrictive assumptions of this study, the results are highly indicative regarding the risks of hazardous zones.

• Geomechanics and Engineering
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• v.29 no.1
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• pp.91-97
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• 2022

The cohesive non-swelling soil (CNS) cushion technology has been widely applied in the subgrade and slope improvement at expansive soil regions. However, the mechanism of the inhibition effect of the CNS layer on expansive soil (ES) has not been fully understood. We performed four outdoor model tests to further understand the inhibition effect, including different kinds of upper layer and thickness, under the unidirectional seepage condition. The swelling deformation, soil pressure, and electrical resistivity were constantly monitored during the saturation process. It is found that when a CNS layer covered the ES layer, the swelling deformation and electrical resistivity of the ES layer decreased significantly, especially the upper part. The inhibition effect of the CNS layer increases with the increase of CNS thickness. The distribution of vertical and lateral soil pressure also changed with the covering of a CNS layer. The electrical resistivity can be an effective index to describe the swelling deformation of ES layer and analyze the inhibition effect of the CNS layer. Overall, the CNS deadweight and the ion migration are the major factors that inhibit the swelling deformation of expansive soil.

• Proceedings of the Korean Geotechical Society Conference
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• 2007.09a
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• pp.481-501
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• 2007

Excessive rainfalls due to climatic changes can trigger an increase in rainfall-induced slope failures that pose real threats to both lives and properties. Many high slopes in residual soils could stand at a steep angle, but failed during or after rainfall. Commonly, these slopes have a deep groundwater table and negative pore-water pressures in the unsaturated zone above the groundwater table contribute to the shear strength of soil and consequently to factor of safety of the slope. Stability assessment of slope under rainfall requires information on rate of rainwater infiltration in the unsaturated zone and the resulting changes in pore-water pressure and shear strength of soil. This paper describes the application of unsaturated soil mechanics principles and theories in the assessment of rainfall effect on stability of slope through proper characterization of soil properties, measurement of negative pore-water pressures, seepage and slope stability analyses involving unsaturated and saturated soils. Factors controlling the rate of changes in factor of safety during rainfall and a preventive method to minimize infiltration are highlighted in this paper.

• Tunnel and Underground Space
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• v.13 no.4
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• pp.304-315
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• 2003

In this paper, the DDA method with a new hydro-mechanical algorithm is used to study the effect of rock discontinuities on uplift and seepage in concrete gravity dam foundations. This paper presents an alternative method of predicting uplift and seepage at the base of concrete gravity dams. A sensitivity analysis was carried out to study the importance of several parameters on dam stability such as the orientation, spacing, and location of discontinuities. The study shows that joint water flow and adverse geological conditions could result in unusual uplift at the base of concrete gravity dams, well in excess of what is predicted with the classical linear or hi-linear pressure assumption. It is shown that, in general, the DDA program with the hydro-mechanical algorithm can be used as a practical tool in the design of gravity dams built on fractured rock masses.

• Tunnel and Underground Space
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• v.18 no.1
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• pp.10-19
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• 2008

Most of flooding cases in tunnels are associated with huge inrushes of water due to the fracture zone with very high water head. To find out the causes and countermeasures for flooding cases, a dozen of tunneling cases are studied. Case studies presented here show that if the flooding had been forecasted and pre-drained prior to the tunnel excavation, such accidents could have been prevented. From this observation, we suggest a new horizontal drainage system with pre-investigation and pre-drainage concept. Seepage analyses are performed to analyze the water head reduction effect on the tunnel face by drainage pipes during the construction of subsea tunnels. Drainage system analyses are performed to analyze performance of the drainage system. These analysis results show that the suggested horizontal pre-drainage system provides a clear drainage and water head reducing effect. Finally, the proposed system can be a new alternative to the present water controlling methods applied to subsea tunnels.