• Geomechanics and Engineering
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• v.22 no.6
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• pp.553-564
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• 2020

In this study, a simple numerical approach for a circular tunnel opening in strain-softening surrounding rock is proposed considering out-of-plane stress and seepage force based on Biot's effective stress principle. The plastic region of strain-softening surrounding rock was divided into a finite number of concentric rings, of which the thickness was determined by the internal equilibrium equation. The increments of stress and strain for each ring, starting from the elastic-plastic interface, were obtained by successively incorporating the effect of out-of-plane stress and Biot's effective stress principle. The initial value of the outmost ring was determined using equilibrium and compatibility equations. Based on the Mohr-Coulomb (M-C) and generalized Hoek-Brown (H-B) failure criteria, the stress-increment approach for solving stress, displacement, and plastic radius was improved by considering the effects of Biot's effective stress principle and the nonlinear degradation of strength and deformation parameters in plastic zone incorporating out-of-plane stress. The correctness of the proposed approach is validated by numerical simulation.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.03b
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• pp.387-394
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• 2000

In the present study, laboratory pull-out tests with screw anchors are carried out to investigate behavior characteristics of underground structures applied uplift seepage forces. Small scaled pull-out tests in sand were conducted under saturated condition. And then, it was observed that the upward displacement as well as the pullout load varied with spacing of the anchor. Also, analyses have been performed with the aim of pointing out the effects of various parameters on the group effect of the screw anchors.

• Journal of the Korean Geotechnical Society
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• v.18 no.5
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• pp.221-228
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• 2002

The stability of a tunnel face is one of the most important factors in tunnel excavation. Especially, if a tunnel is located under groundwater level, groundwater may flow into the tunnel face and seepage forces acting on the tunnel face due to groundwater flow may affect seriously the stability of the tunnel face. Therefore, the seepage pressure at the tunnel face should be considered fir the proper design and safe construction of a tunnel. In this paper, the effect of tunnel advance rate on the seepage forces acting on the tunnel face was studied. The finite element program to analyze the groundwater flow around a tunnel with the consideration of tunnel advance rate was developed. Using the program, the parametric study for the effect of the tunnel advance rate and hydraulic characteristics of the ground on the seepage forces acting on the tunnel face was made. From this study, it was concluded that the tunnel advance rate must betaken into consideration as an additional parameter to assess the seepage forces at the tunnel face and a rational design methodology fer the assessment of support pressures required for maintaining the stability of the tunnel face was suggested for undetwater tunnels.

• Journal of the Korean Geotechnical Society
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• v.26 no.5
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• pp.37-48
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• 2010

In this study, the seepage flow monitoring method by the hydraulic head loss rate was developed for the purpose of application to offshore construction site enclosed by cofferdams in which seepage force varies periodically. The amount of the hydraulic head loss rate newly defined in this graph was in a range between 0 and 1. The zero of the rate means the existence of flow with no seepage resistance. The 1 of the rate means no seepage flow through the ground. The closer to 1 the coefficient of determinant in the hydraulic head loss graph is, the more the ground through which seepage water flows is stable. The closer to 0 the coefficient of determinant in the hydraulic head loss graph is, the more the ground through which seepage water flows was unstable and the higher the possibilities of existence of empty space or of occurrence of piping on the seepage flow pass in the ground is. The hydraulic head loss graph makes it possible to monitor sensitively the situation of seepage flow state, and the graph helps to understand easily the seepage flow state at the specific section on the whole cofferdam.

• Geomechanics and Engineering
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• v.13 no.2
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• pp.217-235
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• 2017

The stability prediction of shallow buried tunnels is one of the most difficult tasks in civil engineering. The aim of this work is to predict the state of collapse in shallow tunnel in layered soils by employing non-associated flow rule and nonlinear failure criterion within the framework of upper bound theorem. Particular emphasis is first given to consider the effects of dilation on the collapse mechanism of shallow tunnel. Furthermore, the seepage forces and surface settlement are considered to analyze the influence of different dilation coefficients on the collapse shape. Two different curve functions which describe two different soil layers are obtained by virtual work equations under the variational principle. The distinct characteristics of falling blocks up and down the water level are discussed in the present work. According to the numerical results, the potential collapse range decreases with the increase of the dilation coefficient. In layered soils, both of the single layer's dilation coefficient and two layers' dilation coefficients increase, the range of the potential collapse block reduces.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.03a
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• pp.792-802
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• 2008

If a tunnel is constructed below the groundwater level, the groundwater flow will occur inducing the seepage force toward the tunnel and will result in the increase of tunnel convergence. The longitudinal deformation during tunnel excavation will also be increased due to seepage pressure. A back-analysis methodology in underwater tunnel was proposed in this study based on the relative longitudinal deformation measured in-situ. Geotechnical parameters can be estimated utilizing the proposed method where the prior estimate as well as the measured convergence can be reasonably combined by adopting the Extend Bayesian Method.

• Journal of the Korean GEO-environmental Society
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• v.2 no.2
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• pp.51-58
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• 2001

The primary objective of this paper was to study the seepage and the failure behavior of unreinforced and reinforced embankment, respectively. Experimental study was conducted to examine the infiltration characteristics. The embankment infiltration tests were conducted with water level condition(h=15cm, 25cm, 35cm), slope inclination(1:1.5, 1:2.0), and the rising velocity(1.25cm/min, 2.5cm/min), respectively. From the model test results, as the slope inclination is decreased, the rising velocity of seepage line increased with both reinforced and unreinforced embankment. With the unreinforced embankment, the rising velocity of water level was faster and the failure circle is lager than those of reinforced ones. And the reinforced embankment with geotextile was safer against seepage force than that of the unreinforced embankment.

• Journal of Korean Tunnelling and Underground Space Association
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• v.13 no.6
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• pp.431-450
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• 2011

When a circular vertical shaft is constructed below the groundwater level, additional forces caused by groundwater flow besides horizontal effective stresses will act on the wall. The inward direction of the groundwater flow will be inclined to the vertical wall and its direction will change depending on the wall depth. In this paper, to figure out the effect of seepage forces acting on the circular vertical shaft, the slope of the inclined flow varying with the depth is divided into vertical and horizontal components to derive the coefficient of earth pressure considering the seepage pressure and to obtain the vertical stress by taking the seepage pressure into account. The control volume in this study is assumed to be the same with that of the dry ground condition within which the earth pressure is acting on the wall by the creation of the plastic zone during shaft excavation. An example study shows that the vertical stress increases by about 1.4 times and the horizontal earth pressure increases up to 2.5 times compared to the dry ground condition. The estimated values from the proposed equation considering seepage forces and the calculated values from numerical analysis with "effective stress plus seepage force" show similar values, which verifies appropriateness of the proposed equation to estimate the earth pressure under the seepage condition.

• Proceedings of the Korean Institute of Industrial Safety Conference
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• 2003.10a
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• pp.207-213
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• 2003

본 연구는 양수발전 등을 목적으로 축조한 소형 Dam 및 Sand Levee의 수위가 급상승할 경우 제체의 내측면에 미치는 영향을 Bishop's simplified method를 사용하여 Seepage Force(침투력)의 항을 중심으로 분석한 것이다. 특히 침투력의 항은 제체의 사면경사가 급할 경우 및 수위의 상승속도에 따라 제체의 안전성에 많은 영향을 미친다.(중략)

• KSCE Journal of Civil and Environmental Engineering Research
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• v.5 no.4
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• pp.15-22
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• 1985

The author has studied the collapse of a slope with seepage occuring in sand model with a trapezodial cross section. The primary objective of this study was to examine the failure phenomenon of embankment with respect to change in void pressure at embankment slope. The contents of this experiments are as follows; 1) Determination of exit point by seepage line. 2) Evaluation of partial failure at exit point. 3) The effects of seepage force at embankment.