• Proceedings of the Korean Geotechical Society Conference
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• 2010.03a
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• pp.1417-1424
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• 2010

To provide more safe road and better travelling service for Expressway customer, we minimize settlement of bridge backfill and properly repair the occurred settlement. So, we devide this study to two parts one is construction part and the other is management part, in construction part we remove settlement occuring elements and in management part we grasp proper repair time, and then we produce general settlement management program. In construction part, for the purpose of developing construction method of reducing settlement, we developed construction method models and they are composed of abutment back section alteration and backfill material alteration by literature reviews and site investigation of backfill settlement. And then, we carried out laboratory model test and full size field test of some developed models.

• 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.

• 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.

• Journal of Korean Tunnelling and Underground Space Association
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• v.20 no.2
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• pp.433-452
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• 2018

The shield tunneling method can minimize surface settlements by preventing the deformation of tunnel face and tunnel intrados due to tunnel excavation. For this purpose, it is very important to control the operating conditions of shield TBM. The face pressure and backfill pressure for tail void grouting should be the most important and immediate measure not only to restrain surface settlement, but also to influence the effective stress and pore water pressure around the circumstance of tunnel during excavation. The reaction of the ground to the application of face pressure and backfill pressure relies on the stiffness and permeability of ground. Especially, the reaction of saturated clayey ground formations, which shows the time-dependent deformation, is different from the permeable ground. Hence, in this paper it was investigated how the TBM operating conditions, ground stiffness, and permeability impact on the surface settlement of saturated clayey ground. For this purpose, a series of parametric studies were carried out by means of the stress-pore water pressure coupled FE analysis. The results show that the settlement of soft clayey ground is divided into the immediate settlement and consolidation settlement. Especially, the consolidation settlement depends on the ground stiffness and permeability. In addition, the existence of critical face pressure and backfill pressure was identified. The face pressure and backfill pressure above the critical value may cause an unexpected increase in the ground settlement.

• Journal of the Korean GEO-environmental Society
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• v.16 no.12
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• pp.13-22
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• 2015

Developed ground cavity due to leakage of decrepit old sewer pipe causes ground surface settlement and brittle fracture of pavement. Recently, for 5 years, frequency of occurrence of ground subsidence phenomenon tends to increase rapidly and/or steadily. It is difficult to investigate ground surface settlement and/or subsidence in urban area because most ground surfaces are covered with asphalt or concrete pavement. In this research, therefore, ground surface settlement, influence zone and settlement of sewer pipe were analyzed using finite element method. Not only reinforced effect of pseudo-plastic backfill that is applied to prevent ground surface settlement or subsidence spot, was compared and analyzed using numerical analysis program, but also direct shear test was carried out to determine strength parameters of pseudo-plastic backfill.

• Proceedings of the Korean Geotechical Society Conference
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• 2004.03b
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• pp.952-957
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• 2004

Cut and Cover Method is generally used in shallow tunnels and tunnel entrances with thin soil cover. In this type of cons0truction, backfilling is considered to be the most important process. In this process even though the backfill material is thoroughly compacted, compaction and self-weight due to vehicular vibration and pressure exerted by the soil cause the backfill material to undergo self-compression which leads to settlement. The settlement of the backfill material subjects the tunnel lining under excessive earth pressure which cause cracking and deformation. In the model test performed installation of geotextile on the sides and top of the tunnel was able to reduce the earth pressure acting on the tunnel lining.

• Journal of Korean Tunnelling and Underground Space Association
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• v.17 no.3
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• pp.305-317
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• 2015

This paper is to perform 3-dimensional numerical analysis considering face pressure, backfill pressure, excavation length, soil model and element size for selecting key factors of ground surface settlement due to shield TBM advancement. According to the numerical analysis results, backfill pressure and soil model are governing factors inducing ground surface settlement. To complement this study, the ground conditions and characteristics of the boring machine will be considered using numerical analysis.

• Journal of the Korean Geosynthetics Society
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• v.14 no.3
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• pp.13-20
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• 2015

Inappropriate backfill material and poor compaction cause the damage to sewer and ground settlement. To deal with such problem, flowable backfill material has attracted attention recently. A basic study was conducted in a bid to obtain optimum mixing ratio of backfill material with the characteristics of rapid hardening, pseudo-plasticity, flowability and anti washout ability and enhance the cost efficiency of backfill material. Through the test of optimal mixing ratio of rapid hardening, evaluation of optimal mixing ratio of backfill material was conducted. As a result, required performance as well as cost efficiency could be achieved by adjusting plasticizer even in case of increasing W/M of the paste of rapid hardening to 100%.

• Journal of Korean Tunnelling and Underground Space Association
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• v.20 no.2
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• pp.375-392
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• 2018

The shield TBM method is widely adopted for tunneling works in urban area because it has more beneficial ways to control settlement at ground surface than conventional mined tunneling. In the shield tunneling, backfill grouting at tail void is crucial because it is supposed not only to restraint ground deformation around tail void during excavation but also to compensate precedent ground settlement by pushing up the ground with highly pressurized grout. However, the tail void grouting has been found to be ineffective for settlement compensation particularly in sandy ground, which might be caused by complicate interaction between ground and tail void grouting. In this paper, the effects of tail void grouting on behavior of ground in shield TBM tunneling were investigated based on 3-dimensional finite element analyses. The results of numerical analyses indicated that backfill grouting actually reduces settlement by degrading settlement increasing rate in excavation, which means decrease of volume loss. Meanwhile, the grouting could not contribute to compensate the precedent settlement, because reduction of volume loss by grouting was found to be counterbalanced by volume change of ground.

• Journal of the Korean Geosynthetics Society
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• v.17 no.1
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• pp.85-93
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• 2018

A existing standard design section of transitional zone between bridge and earthwork section in high speed railway should be designed to gradually change support stiffness from bridge abutment to backfill side that were placed on cemented stabilized gravel, general gravel, soil materials. The larger the backfill slope of the general gravel and soil was more structurally stable, but there is no clear reason about them. In this study, it was compared with settlement and bearing capacity of backfill area in currently design and alternating backfill slope section using large centrifuge tester. As the experimental results, it was showed that the 1:2 slope and 1:1.5 slope have almost similar bearing capacity behavior under the load stage as railway loading level.