• Journal of the Korean Geosynthetics Society
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• v.3 no.1
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• pp.3-15
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• 2004

Geogrid reinforced soil structures with segmental block facing have been increased since 1990's, because of the convenience of installation and the flexible appearance. In this paper, the behavior of the segmental reinforced retaining wall was analysed with the results of field monitoring. The height and length of reinforced wall are 12m and 25m, respectively. The field measurement equipments are horizontal and vertical earth pressure cells, settlement plate, strain gauge, inclinometer, and displacement pin. Based on the field monitoring, the horizontal earth pressure was approximately 0.3times higher than that of the theoretical method and the maximum tensile strength of reinforcement was 26.2kN/m. The displacement of facing wall was 23mm at the point of 7.1m height of the wall and toward the wall facing. The results of the study indicate that the segmental reinforced retaining wall is in a stable condition because of good compaction & reinforcement effects, and long period of construction time. Finally, the computer program of SRWall is very useful tool to design the segmental reinforced retaining wall.

• Journal of the Korean Geosynthetics Society
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• v.16 no.4
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• pp.231-240
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• 2017

Recently, there have been frequent occurrences of ground sink in the urban area, which have resulted in human and material damage and are accompanied by economic losses. This is caused by artificial factors such as soil loss, poor compaction, horizontal excavation due to the breakage of the aged sewage pipe, and lack of water proof at vertical excavation. The ground sink can be prevented by preliminary restoration and reinforcement through exploration, but it can be considered that it is not suitable for urgent restoration by the existing method. In this study, a model experiment was carried out to simulate the in-ground cavities caused by groundwater flow for developing non-excavation urgent restoration in underground cavity and the range of the relaxation zone was estimated by detecting the around the cavity using a relaxation zone detector. In addition, disturbance region and relaxation region were separated by injecting gypsum into cavity formed in simulated ground. The shape of the underground cavity due to the groundwater flow was similar to that of the failure mode III formed in the dense relative density ground due to water pipe breakage in the previous study. It was confirmed that the relaxed region detected using the relaxation zone detector is formed in an arch shape in the cavity top. The length ratio of the relaxation region to the disturbance region in the upper part of the cavity center is 2: 1, and it can be distinguished by the difference in the decrease of the shear resistance against the external force. In other words, it was confirmed that the secondary damage should not occur in consideration of the expandability of the material used as the injecting material in the pre-repair and reinforcement, and various ground deformation states will be additionally performed through additional experiments.

• The Journal of Engineering Geology
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• v.19 no.2
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• pp.191-203
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• 2009

The effect of stabilizing piles on cut slopes is checked and the behavior of slope soil and piles are observed throughout the year by field measurements on the large-scale cut slopes. First of all, the behavior of the slope soil was measured by inclinometers during slope modification. Landslides occurred in this area due to the soil cutting for slope modification. The horizontal deformations of slope soil are gradually increased and rapidly decreased at depth of sliding surface. As the result of measuring deformation, the depth of sliding surface below the ground surface can be known. Based on the measuring the depth of the sliding surface, some earth retention system including stabilizing piles were designed and constructed in this slope. To check the stability of the reinforced slope using stabilizing piles, an instrumentation system was installed. As the result of instrumentation, the maximum deflection of piles is measured at the pile head. It is noted that the piles deform like deflection on a cantilever beam. The maximum bending stress of piles is measured at the soil layer. The pile above the soil layer is subjected to lateral earth pressure due to driving force of the slope, while pile below soil layer is subjected to subgrade reaction against pile deflection. The deflection of piles is increased during cutting slope in front of piles for the construction of soil nailing. As a result of research, the effect and applicability of stabilizing piles in large-scale cut slopes could be confirmed sufficiently.

• Journal of the Korean Geotechnical Society
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• v.28 no.8
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• pp.21-29
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• 2012

At-rest lateral stress coefficient that is used for the evaluation of geotechnical structures such as foundations and retaining walls plays a significant role in the analysis and design, as a state variable of in-situ stress condition. In the widely applied Jaky's Ko equation stress condition can be inferred from the internal friction angle obtainable from the laboratory experimentation whereas the eguation mares it challenging to evaluate the influences and criteria of particle characteristics which is essential for the application of friction angles in practices. Thus, this study experimentally explored the behaviors of Ko depending on the relative density, particle shape, and surface roughness effect during a range of loading stages. The Ko values of Jumumjin sand, glass beads, and etched glass beads were measured using a customized Ko device housing strain gauges during loading-unloading-reloading steps, and the effect of dominant factors on Ko is analyzed. Results show that the high Ko prevails for both round and angular specimens with low relative density and the surface roughness has a nominal effect. The angular particles exhibit low Ko for specimens with similar relative density. The characteristics of relevance between Ko and friction angles with varying relative density are also investigated based on the experimental results using empirical correlations and previously reported values.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.13 no.5
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• pp.109-122
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• 1993

ln this paper, a finite element analysis procedure is proposed for the incremental multi-step excavations in a fluid-saturated porous medium such as saturated soil ground. As the basis of derivation, Biot's equation was used. The proposed procedure was applied to some one- and two-dimensional problems under incremental excavations. Unsaturated cases as well as saturated cases were considered for comparison. Through numerical tests, the effects of permeability and excavation speed on the deformation history was investigated. Results showed that pore pressure built up during incremental excavation has a significant effect on the deformation and stresses of solid skeleton and validated the use of the present procedure for the analysis of multi-step excavations in fluid-saturated media such as in saturated shallow ground.

• Journal of KSNVE
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• v.10 no.6
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• pp.1075-1082
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• 2000

The paper describes the vibration and stability of tapered beams on two-parameter elastic foundations. The two-parameter elastic foundations are constructed by distributed Winkler springs and a shearing layer as of ten used in soil models. The shear deformation and the rotatory inertia of a beam are taken into account. Governing equations are derived from energy expressions using Hamilton\`s principle. The associated eigenvalue problems are solved to obtain the free vibration frequencies or the buckling loads. Numerical results for the vibration of a beam with an axial force are presented and compared when other solutions are available. Vibration frequencies, mode shapes, and critical forces of a tapered Timoshenko beam on elastic foundations under an axial force are investigated for various thickness ratios, shear foundation parameters, Winkler foundation parameters and boundary conditions.

• International Journal of Highway Engineering
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• v.10 no.4
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• pp.31-40
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• 2008

The dynamic moduli of asphalt concrete are very important for the analysis and the design of asphalt pavement systems. The dynamic modulus master curve is usually represented by a sigmoidal function. The Ramberg-Osgood model was widely used for fitting of normalized modulus reduction curves with strain of soils in soil dynamic fields. The master curves were obtained by both sigmoidal functions and modified Ramberg-Osgood model for the same dynamic modulus data set, the fitting abilities of both methods were excellent. The coefficients in sigmoidal function are coupled. Therefore, it is not possible to separate the characteristics of the master curve with absolute value and shape. However, the each fitting coefficient in the Ramberg-Osgood model has a unique effect on the master curve, and the coefficients are not coupled with each other.

• Journal of Korean Tunnelling and Underground Space Association
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• v.13 no.4
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• pp.347-370
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• 2011

Slurry type shield would be very effective for the tunnelling in a sandy ground, when the slurry pressure would be properly adjusted. Low slurry pressure could cause a tunnel face failure or a ground settlement in front of the tunnel face. Thus, the stability of tunnel face could be maintained by applying an excess slurry pressure that is larger than the active earth pressure. However, the slurry pressure should increase properly because an excessively high slurry pressure could cause the slurry flow out or the passive failure of the frontal ground. It is possible to apply the high slurry pressure without passive failure if a horizontal impermeable layer is located in the ground in front of the tunnel face, but its location, size, and effects are not clearly known yet. In this research, two-dimensional model tests were carried out in order to find out the effect of a horizontal impermeable layer for the slurry shield tunnelling in a saturated sandy ground. In tests slurry pressure was increased until the slurry flowed out of the ground surface or the ground fails. Location and dimension of the impermeable layer were varied. As results, the maximum and the excess slurry pressure in sandy ground were linearly proportional to the cover depth. Larger slurry pressure could be applied to increase the stability of the tunnel face when the impermeable layer was located in the ground above the crown in front of the tunnel face. The most effective length of the impermeable grouting layer was 1.0 ~ 1.5D, and the location was 1.0D above the crown level. The safety factor could be suggested as the ratio of the maximum slurry pressure to the active earth pressure at the tunnel face. It could also be suggested that the slurry pressure in the magnitude of 3.5 ~4.0 times larger than the active earth pressure at the initial tunnel face could be applied if the impermeable layer was constructed at the optimal location.

• Journal of the Korean Geotechnical Society
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• v.34 no.10
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• pp.61-74
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• 2018

In this study, the pull-out behavior of tunnel type anchorage of suspension bridges was analyzed based on results from laboratory size model tests and numerical analysis. Tunnel type anchorage has found its applications occasionally in both domestic and oversea projects, therefore design method including failure mode and safety factor is yet to be clearly established. In an attempt to improve the design method, scaled model tests were conducted by employing simplified shapes and structure of the Ulsan grand bridge's anchorage which was the first case history of its like in Korea. In the model tests, the anchorage body and the surrounding rocks were made by using gypsum mixture. The pull-out behavior was investigated under plane strain conditions. The results of the model tests showed that the tunnel type anchorage underwent wedge shape failure. For the verification of the model tests, numerical analysis was carried out using ABAQUS, a finite element analysis program. The failure behavior predicted by numerical analysis was consistent with that by the model tests. The result of numerical analysis also showed that the effect of Poisson's ratio was negligible, and that a plugging type failure mode could occur only when the strength of the surrounding rocks was 10 times larger than that of anchorage body.

• Journal of the Korean Geotechnical Society
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• v.21 no.5
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• pp.33-43
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• 2005

This work reports results of our study on the dynamic responses of the buried pipelines both along the axial and the transverse directions under various boundary end conditions. In order to investigate the effect of the boundary end conditions for the dynamic responses of the buried pipeline, we have devised a computer program to find the solutions of the formulae on the dynamic responses (displacements, axial strains, and bending strains) under the various boundary end conditions considered in this study, The dynamic behavior of the buried pipelines for the forced vibration is found to exhibit two different forms, a transient response and a steady state response, depending on the time before and after the transfer of a seismic wave on the end of the buried pipeline. We have observed a resonance when the mode wavelength matches the wavelength of the seismic wave, where the mode number(k) of resonance f3r the axial direction. On the other hand, we have not been able to observe a resonance in the analysis of the transverse direction, because the dynamic responses are found to vanish after the seventh mode. From the results of the dynamic responses at many points of the pipeline, we have found that the responses appeared to be dependent critically on the boundary end conditions. Such effects are found to be most prominent especially for the maximum values of the displacement, the strain and its position.