• Journal of Korean Tunnelling and Underground Space Association
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• v.20 no.2
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• pp.269-286
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• 2018

Backfill injection pressure in shield TBM affects not only ground settlement but also adjacent underground structures. Therefore, it is essential to estimate a suitable backfill injection pressure in advance in design stage. In this paper, seven suggested equations worldwide to calculate the backfill injection pressure were reviewed and compared. By assuming 6 cases of virtual ground condition, backfill injection pressures were calculated and analyzed. it was confirmed that the backfill injection pressure increases as the depth of overburden increases, but the increasing ratio decreases. The numerical analysis was carried out by applying the calculated backfill injection pressure to investigate the influence of backfill injection pressure on the settlement of surface and crown of tunnel. It was confirmed that the final settlement at the surface and crown of tunnel on the both unsaturated and saturated condition are more influenced by the applied face pressure than the applied backfill injection pressure. In addition, the effect of backfill injection pressure decreases as the depth of overburden increases, and the effect of backfill injection pressure increases as the applied face pressure decreases.

• Proceedings of the KSR Conference
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• 2005.05a
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• pp.661-666
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• 2005

In this Paper, to calculate vertical earth pressure affected from several factors in case of rigid buried pipe with cohesionless backfill soil. The result from PENTAGON 3D is compared with several equation's result such as the Janssen, Marston, Spangler, Handy's equation. Result of study shows that vertical earth pressure of each equation is affected by backfill width, backfill depth and wall friction. And vertical earth pressure is linearly increased with backfill depth and backfill width. Marston's equation and Handy's equation are overestimated and FEM(Finite Element method) analysis and Janssen's Silo equation are affected by more backfill depth than backfill width.

• Journal of the Korean Geotechnical Society
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• v.15 no.4
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• pp.261-277
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• 1999

The horizontal and vertical earth pressures in backfill space which is narrowly excavated like ditch are affected by the share of ditch backfill space and the wall friction between excavated surface and backfill soil. In this paper, for the excavated surface the Handy's equation of a symmetric vertical case and the Kellogg's equation of a symmetric sloped one are modified to show the minor principal stress arch for the unsymmetrical excavated backfill space. Compared with the soil test box result, a similarity in magnitude and distribution of backfill earth pressure shows that the earth pressure has been observed. The backfill earth pressure in unsymmetrically sloped space has been shown twice as much as the one in vertically excavated space and also remarkable decline of arching for the former case. It is verified that the earth pressure equation should account the shape and size of backfill space to calculate the earth pressure for similar structure to the one handled in this study.

• Nuclear Engineering and Technology
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• v.44 no.1
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• pp.89-102
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• 2012

The buffer and backfill are important components of the engineered barrier system in a high-level waste repository, which should be constructed in a hard rock formation at a depth of several hundred meters below the ground surface. The primary function of the buffer and backfill is to seal the underground excavation as a preferred flow path for radionuclide migration from the deposited high-level waste. This study investigates the hydraulic conductivity and swelling pressure of Kyungju Ca-bentonite, which is the candidate material for the buffer and backfill in the Korean reference high-level waste disposal system. The factors that influence the hydraulic conductivity and swelling pressure of the buffer and backfill are analyzed. The factors considered are the dry density, the temperature, the sand content, the salinity and the organic carbon content. The possibility of deterioration in the sealing performance of the buffer and backfill is also assessed.

• Journal of Ocean Engineering and Technology
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• v.24 no.5
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• pp.39-47
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• 2010

In this paper, a total stress analysis method for gravity quay walls is suggested. The method can evaluate the displacement of the quay walls considering the effect of excess pore pressure developed in backfill soils. This method changes the stiffness of backfill soils according to the expected magnitude of the excess pore pressure. For practical application, evaluation methods are suggested for determining the excess pore pressure ratio developed in the backfill soils and the backfill stiffness that corresponds to the excess pore pressure ratio. This method is important in practical applications because the displacement of the quay walls can be evaluated by using only the basic input properties in the total stress analysis. The applicability of the suggested method was verified by comparing the results of the analysis with the results of 1-g shaking table tests. From the comparison, it was found that the calculated displacements from the suggested method showed good agreement with the measured displacements of the quay walls. It was also found that the excess pore pressure in backfill soils is a governing influence on the dynamic behavior of quay walls.

• Journal of the Korean Geotechnical Society
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• v.22 no.1
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• pp.15-23
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• 2006

During earthquake, force components acting on quay walls consist of inertia force, earth pressure and water pressure. The earth pressure is largely influenced by the backfill condition such as soil density and the installation of gravel backfill. Therefore, shaking table tests were performed by using four different model sections, which were designed by varying the soil density and the backfill materials. The magnitude and the phase of force components acting on quay wall were analyzed. Test results showed that the gravel backfill and the soil compaction were effective to reduce the excess pore pressure in backfill and the magnitude and phase of backfill thrust were much influenced by the excess pore pressure in backfill. When the input acceleration was 0.10g, the average ratios of the inertia force, the front dynamic water force and the thrust to the total force were $64\%,\;21\%\;and\;16\%$, respectively. As the excess pore pressure increased, the ratio of the thrust to the total force increased.

• Journal of Ocean Engineering and Technology
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• v.14 no.1
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• pp.74-79
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• 2000

The purpose of this paper is to recycle coal ash as structural backfill materials from electric power plants. Two million tons of coal ash are produced annually. The laboratory test was executed for the basic compatibility as substitution for structural backfill materials and the optimal mixture ratio(fly ash : bottom ash) was decided. In addition the model test was performed using medium scale earth pressure model with small size earth pressure cells model box data logger and some other apparatuses. Mixed coal ash and excellent backfill materials(coheisonless soil SW) were compared in the view of lateral earth pressure variation depending on wall displacement. The reduction of earth pressure when coal ash was used as a bockfill material was monitored comparing to that of cohesionless soil. the cost and environmental pollutants by treating coal ash can be reduced through developing the recycling technology.

• Geomechanics and Engineering
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• v.15 no.3
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• pp.823-831
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• 2018

The most important issue during shield TBM tunneling in soft ground formations is to appropriately control ground surface settlement. Among various operational conditions in shield TBM tunneling, the face pressure and backfill pressure should be the most important and immediate measure to restrain surface settlement during excavation. In this paper, a 3-D hydro-mechanical coupled FE model is developed to numerically simulate the entire process of shield TBM tunneling, which is verified by comparing with real field measurements of ground surface settlement. The effect of permeability and stiffness of ground formations on tunneling-induced surface settlement was discussed in the parametric study. An increase in the face pressure and backfill pressure does not always lead to a decrease in surface settlement, but there are the critical face pressure and backfill pressure. In addition, considering the relatively low permeability of ground formations, the surface settlement consists of two parts, i.e., immediate settlement and consolidation settlement, which shows a distinct settlement behavior to each other.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.03b
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• pp.435-440
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• 2000

It is important to pay careful attention to construction backfill for the structural integrity of concrete box culvert. The stability of the surrounding soil is important to the structural performance of most culverts. Good compaction by the dynamic compaction roller with big capacity is as effective as good backfill materials to increase the structural integrity of culvert. However structural distress of the culvert could be occur due to the excessive earth pressure by dynamic compaction load. In this study, 16 box culverts were constructed with various compaction materials and construction methods. Three types of on-site soils such as subbase, subgrade and roadbed materials were used as backfill materials in the test program. Compaction methods were adapted based on the site conditions. In most cases, dynamic compaction rollers with 10 to 16 ton weights were used and vibration speed were applied from 2400 to 2500 rpm for the great compaction energy. Some backfill compactions with good quality soils were carried out to examine the effect of EPS(Expanded Polystyrene) panels with changes of compaction thickness. This paper presents the main results of the research conducted to access the engineering performance of the backfill materials. The characteristics of earth pressures are discussed. It is observed that subgrade and roadbed materials are needed more careful compaction than subbase materials. It is shown that EPS panels are effective to mitigate dynamic lateral earth pressure on the culverts. It is also obtained that the dynamic pressure depends on the soil properties. In addition, the coefficient of dynamic earth pressure (K$\sub$dyn/=ΔP$\sub$H/ ΔP$\sub$V/) during compaction is discussed.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.11a
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• pp.87-94
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• 2000

This paper concerns the distribution of earth pressures on a cantilever wall with unattached reinforcements in the backfill. This type of walls is different from the existing reinforced earth walls in that unattached reinforcements are placed in the backfill of rigid retaining wall such as gravity wall and cantilever wall, instead of connecting reinforcements to the wall segments. Two large-scale prototype tests have been carried out with a 4m high cantilever wall; one with unreinforced backfill, the other with unattached strips in the backfill. The reinforcing effect of unattached strips are discussed based on the earth pressure distribution measured in two large-scale prototype tests. Also, the comparison between measured and predicted earth pressure on a wall with unattached strips are discussed herein to confirm the validity of analytical prediction.