• Journal of the Korean Geotechnical Society
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• v.18 no.5
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• pp.251-260
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• 2002

Geotextile tribes are made of sewn geotextile sheet and hydraulically or mechanically filled with dredged materials. They have been applied in hydraulic and coastal engineering in recent years(shore protection structure, detached breakwater, groins, and jetty). Therefore, it is composed of geotextile and confined fill material. Recently, new preliminary design criteria supported by model and prototype tests, and some stability analysis calculations have been studied. The stability analysis of geotextile tube is composed of geotechnical and hydrodynamic analysis. The stability check points are sliding failure, overturning, bearing capacity failure against the wave attack. In this paper are presented the stability analysis method by empirical equation and 2-D equilibrium analysis for geotextile tube. Also, the hydraulic model tests were performed to verify the theoretical stability analysis with geotextile tube shape, filling ratio, significant wave height, and so on. The results of this study show that the stability of geotextile tube depends on the tube shape, contact area, projection area. The theoretical analysis and hydraulic model test show almost the same results.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.22 no.6
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• pp.415-422
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• 2010

Development of the reliability-based design program in the GUI environment is inadequate for engineers familiar with the deterministic design to deal with the international design criterion based on the probabilistic design. In this study, the design program based on the GUI environment is developed in order to more efficiently input the design factor and more easily carry out the design works. The GUI environment is the GUIDE (Graphic User Interface Development Environment) tool supported by the latest MATALB version 7.1. In order to test the model reliability, the probabilities of failure (POF) on the breakwater armor block (AB) and gravity quay-wall (QW) in the sliding mode are computed using the model in the Level II and Level III. The POF are 55.4~55.7% for breakwater AB and 0.0006~0.0007% for gravity QW. A non-GUI environment program results of the POF are 55.6% for breakwater AB and 0.0018% for gravity QW. In comparison, the POF difference is negligible for breakwater AB because the exact input design parameters are available, whereas the large POF difference, but within the same order, for gravity QW can be explained by the difference of the input design factors because of the poor input data information.

• Journal of the Korean GEO-environmental Society
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• v.16 no.4
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• pp.5-12
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• 2015

Civil engineers have taken the numerous slope monitoring data for an engineering project subjected to hazard potential of slide. However, the topics on how to deal with and draw out proper information from the data related to the slope behavior have not been widely discussed. Recently, several researchers had installed the real-time monitoring system to cope with slope failure; however they are mainly focused on the hardware system installation. Therefore, this study tries to show how the measured data could be grouped and connected each other. The basic idea of analyzing method studied in this paper came from the clustering, which is the part of data mining analysis. Therefore, at the base of classification of time series data, the authors suggest three mathematical data analyzing methods; Average Index of different displacement ($AD_{i,j}$), Difference of average relative displacement ($\overline{RD}_{i,j}$) and Coordinate system of average and relative displacement ($\overline{RD}$, AD). These analyzing methods are based on the statistical method and failure mechanism of slope. Therefore they showed clustering relationships of the similar parts of the slope which makes the same sliding mechanism.

• Economic and Environmental Geology
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• v.38 no.3 s.172
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• pp.305-317
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• 2005

This study addresses the preliminary results of rock slope stability analyses including hazard assessments for slope failure conducted on the selected sections of rural road cut slope which are about 4 km long. The study area is located in the Mt. Chuntae northeast of Busan and mainly composed of Cretaceous rhyolitic ash-flow tuff', fallout tuff, rhyolitc and andesite. The volcanic rock mass in the area has a number of discontinuities that produce a potentially unstable slope, as the present cut slope is more than 70 degrees in most of the slope sections. Discontinuity geometry data were collected at selected 8 scanline sections and analyzed to estimate important discontinuity geometry parameters to perform rock slope kinematic and block theory analyses. Kinematic analysis for plane sliding has resulted in maximum safe slope angles greater than $65^{\circ}$ for most of the discontinuities. For most of the wedges, maximum safe cut slope angles greater than $45^{\circ}$ were obtained. Maximum safe slope angles greater than 80" were obtained fur most of the discontinuities in the toppling case. The block theory analysis resulted in the identification of potential key blocks (type II) in the SL4, SL5, SL6 and SL8 sections. The chance of sliding taking place through a type ll block under a combined gravitational and external loading is quite high in the investigated area. The results support in-field observations of a potentially unstable slope that could become hazardous under external forces. The results obtained through limit equilibrium slope stability analyses show how a stable slope can become an unstable slope as the water pressure acting on joints increases and how a stable slope under Barton's shear strength criterion can fail as the worst case scenario of using Mohr-Coulomb criterion.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.1
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• pp.181-194
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• 2013

Landslides are known as gravitational mass movements that can carry the flow materials ranging in size from clay to boulders. The various types of landslides are differentiated by rate and depositional features. Indeed, flow characteristics are observed from very slow-moving landslides (e.g., mud slide and mud flow) to very fast-moving landslides (e.g., debris avalanches and debris flows). From a geomechanical point of view, shear-rate-dependent shear strength should be examined in landslides. This paper presents the design of advanced ring-shear apparatus to measure the undrained shear strength of debris flow materials in Korea. As updated from conventional ring-shear apparatus, this apparatus can evaluate the shear strength under different conditions of saturation, drainage and consolidation. We also briefly discussed on the ring shear apparatus for enforcing sealing and rotation control. For the materials with sands and gravels, an undrained ring-shear test was carried out simulating the undrained loading process that takes place in the pre-existing slip surface. We have observed typical evolution of shear strength that found in the literature. This paper presents the research background and expected results from the ring-shear apparatus. At high shear speed, a temporary liquefaction and grain-crushing occurred in the sliding zone may take an important role in the long-runout landslide motion. Strength in rheology can be also determined in post-failure dynamics using ring-shear apparatus and be utilized in debris flow mobility.

• Journal of the Korean Geosynthetics Society
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• v.18 no.4
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• pp.151-165
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• 2019

In this study, the four types of improvement methods (increase self weight and reducing sliding force etc.) were proposed depending on install location with compaction grouting to improve seismic performance of existing port structure and optimal methods by analyzing the effects of improvement (stability, constructability and economy) by theoretical and numerical methods. From the dynamic time history analysis for artificial seismic waves, the results indicated that the horizontal displacement after improvement decreased compared to before improvement, however the displacement reduction effect among improvement methods was not significantly different. Slope stability based on the strength reduction method and the limit equilibrium analysis method, it is confirmed that the passive pile method is more safe than other methods. It is due to the shear strength at the failure surface is increased. In addition, the analysis of constructability and economy showed that the reduction of earth pressure method (type 02) and the passive pile method (type 03) are excellent. However, in the case of the passive pile method is concerned that there is a shortage of design cases and the efficiency can be reduced depend on various constraints such as ground conditions.

• Journal of Korean Tunnelling and Underground Space Association
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• v.2 no.2
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• pp.50-61
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• 2000

The ground around the portal of a tunnel is the most typical part showing the 3-dimensional mechanical behavior in the tunnel. The portal slope is constructed at the weathered soft rock-mass, and remains as a potential sliding mass. The slope failure around the tunnel portal may happen drastically and induce the great disaster; hence, for the permanent stability several special techniques are required. To solve this problem, the ground around the tunnel portal may be excavated in the arch shape to develop the arching effect in horizontal direction. With the arch-type portal slope, one can reduce considerably the excavation mass and the damage of environments. This approach has not been attempted yet due to the lack of understanding and the well-defined analyzing method, so the retaining wall type portal is more universal. The 3-dimensional finite element analyses were carried out to prove that the arch type is more advantageous in safety and cost than the right angle type. The influence of the tunnel construction sequence and the strength of the rock-mass on the slope stability was investigated by focusing on the maximum shear strain in the slope, and the yield zone at the tunnel face.

• Journal of the Korean Geosynthetics Society
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• v.12 no.3
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• pp.15-22
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• 2013

By changing from ballasted track to concrete slab track, new type railroad subgrade is strongly required to satisfy strict regulations for displacement limitations of concrete slab track. In this study, sensitivity analysis was performed to assess the design characteristics of new type reinforced railroad subgrade, which could minimize residual settlement after track construction and maintain its function as a permanent railway roadbed under large cyclic load. With developed design program, the safety analysis (circular slip failure, overturning, and sliding) and the evaluation of internal forces developed in structural members (wall and reinforcement) were performed according to vertical installation spacing and stiffness of short and long geotextile reinforcement. Based on this study, we could evaluate the applicabilities of 0.4 H short geogrid length with 0.4 m vertical installation spacing of geotextile as reinforcement and what the ground conditions are for the reinforced railroad subgrade. And also, we could grasp design characteristics of the reinforced railroad subgrade, such as the importance of connecting structure between wall and reinforcement, boundary conditions allowing displacement at wall ends to minimize maximum bending moment of wall.

• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.5
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• pp.1-9
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• 2022

In this study, the in-plane and out-of-plane seismic performance of the masonry wall strengthened using the steel bar truss system proposed by Hwang et al. (2021a, 2021b) or using FRP sheets were compared and evaluated. The maximum strength of the masonry wall reinforced with FRP sheets for the in-plane and out-of-plane loading was 71% and 85%, respectively, of that of the non-reinforced masonry wall. Meanwhile, the maximum strength of the masonry wall reinforced with the steel bar truss system was approximately 1.8 times higher than that of the non-reinforced masonry wall. Compared with the FRP sheet method, the steel bar truss system was excellent at improving the maximum load capacity, rigidity, and energy dissipation capacity. However, in the case of a masonry wall reinforced with FRP sheets, the masonry wall was overstrengthened with the FRP sheets covering the entire masonry wall, and it is considered that the overstrengthened specimen experienced sliding failure, resulting in a lower strength than the other specimens. A follow-up study is needed to compare the seismic performance of the specimen involving only a part of the masonry wall reinforced with the FRP sheets and the specimen reinforced using the steel bar truss system.

• Journal of the Korean Geotechnical Society
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• v.26 no.6
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• pp.29-38
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• 2010

Micro-piles have been used to increase the bearing capacity or to restrain settlement of existing shallow foundation. Recently, micro-piles are used to support the shallow foundation, to stabilize the slope and to resist the sliding of retaining wall. Using the micro-piles in geotechnical engineering, some investigators have studied the effective installing method by model test or field test. But most of previous studies are chiefly focused on the micro-piles in sand or clay layer. If a rock layer exists in soil, the installing length of micro-piles may be determined by the depth of rock layer. In this case, the stiffness of pile may be changed by the installing length of pile, and so the installing method has to be altered by the changed stiffness of pile. Model tests have been conducted to study the installation method of micro-pile in soil with rock layer. As a result, when the ratio of length of pile is below 50 ($L/d{\leq}50$), installing of micro-piles in vertical position is effective regardless of the depth of rock layer. If the depth of rock layer is deeper than soil failure zone and the ratio of the length of pile exceeds 50 (L/d>50), installing of the micro-piles in sloped position is effective.