• Journal of the Korean Geotechnical Society
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• v.19 no.2
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• pp.107-121
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• 2003

When the seismic stability of quay walls is analyzed, the magnitudes of force components acting on quay walls during earthquakes and the phase relations among these force components must be properly evaluated. In general, force components include inertia force of the quay wall, lateral earth force, and water force. The magnitude and the phase relation of each force component vary according to the magnitude of the excess pore pressures developed in backfill soils of the quay wall. The dynamic thrust mobilized at the contact surface between the backfill soil and the wall develops as a result of the interactions among these force components. We propose a simple model to evaluate the magnitude and phase variation of the dynamic thrust on the back of the wall in terms of the excess pore pressure. The proposed model can predict the dynamic thrust by summing the magnitudes of farce components calculated from design equations for seismic pressures on the wall. The proposed model was verified by comparing its results with the results from a series of shaking table tests.

• Journal of the Korean Geotechnical Society
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• v.20 no.3
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• pp.129-139
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• 2004

During the construction of circular underground pipe, the non-proper compaction along the pipe and the decrease of compaction efficiency have been the main problems to induce the failure of underground pipe or facility. The use of CLSM (controlled low strength materials) should be one of the possible applications to overcome those problems. In this research, the small-scaled model test and the numeric analysis using PENTAGON-3D FEM program were carried out for three different cases on the change of backfill materials, including the common sand, the soil from construction site, and the CLSM.. From the model test in the lab, it was found out that the use of CLSM as backfill materials reduced the vertical and lateral deformation of the pipe, as well as the deformation of the gound surface. The main reason for reducing the deformation would be the characteristics of the CLSM, especially self-leveling and self-hardening properties. The measured earth pressure at the surround of the corrugated pipe using the CLSM backfills was smaller than those in the other cases, and the absolute value was almost zero. Judging from the small-scaled model test and FEM analysis, the use of CLSM as backfill materials should be one of the best choices reducing failure of the underground pipes.

• Tunnel and Underground Space
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• v.20 no.5
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• pp.352-359
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• 2010

Stability of twin tunnels depends on the pillar width and the ground condition. In this study, large scale model tests were conducted for investigating the influence of the pillar width of twin tunnels on their behavior in the regular horizontal jointed rock mass. Jointed rocks was composed of concrete blocks. Pillar width of twin tunnels varied in 0.29D, 0.59D, 0.88D and 1.18D, where D is the tunnel width. During the test, pillar stress, lining stress, tunnel distortion, and ground displacement were measured. Lateral earth pressure coefficient was kept in a constant value 1.0. As a result, it was found that the pillar stress and the displacement of the ground and tunnel were increased by decreasing pillar width. The maximum displacement rate was measured just after the upper excavation in each construction sequence. And the maximum influence position was the right shoulder of the preceeding tunnel at the pillar side. It was also found that for the stability assessment the inner displacement was more critical than the crown displacement. The influence zone was formed at the pillar width 0.59D~0.88D that was smaller than 0.8D~2.0D, which was proposed by experience for a good ground condition. And it would be concluded that horizontal joints could also influence on the stability of the twin tunnels.