• Journal of the Korean Geosynthetics Society
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• v.19 no.4
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• pp.95-109
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• 2020

In this study, a total of six site cases were reviewed to assess the site applicability of portable dynamic cone penetration test (DCPT) by identifying the cause of damage to the damaged reinforced earth wall using portable dynamic cone penetration test. An improved dynamic concrete penetration tester was used at the site to enable ground surveys of more than 6 meters. The test results were compared with the results of the standard penetration test (SPT) and the correlation was analyzed. Through the analysis of various field application cases, it was found that portable dynamic cone penetration test was very convenient to apply at the site of the damaged reinforced earth wall, and DCPT could play a major role in identifying the cause of damage and verifying stability of the retaining wall by continuously identifying the ground strength. In addition, it was found that the results of the dynamic cone penetration test and the standard penetration test showed a correlation of N≒(1/3~2/3)·Nd in sandy soil.

• Geomechanics and Engineering
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• v.36 no.6
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• pp.563-573
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• 2024

In this study, various countermeasures used to mitigate tunnel deformations due to nearby multi-propped basement excavation in soft clay are explored by three-dimensional numerical analyses. Field measurements are used to calibrate the numerical model and model parameters. Since concrete slabs can constrain soil and retaining wall movements, tunnel movements reach the maximum value when soils are excavated to the formation level of basement. Deformation shapes of an existing tunnel due to adjacent basement excavation are greatly affected by relative position between tunnel and basement. When the tunnel is located above or far below the formation level of basement, it elongates downward-toward or upward-toward the basement, respectively. It is found that tunnel movements concentrate in a triangular zone with a width of 2 H_e (i.e., final excavation depth) and a depth of 1 D (i.e., tunnel diameter) above or 1 D below the formation level of basement. By increasing retaining wall thickness from 0.4 m to 0.9 m, tunnel movements decrease by up to 56.7%. Moreover, tunnel movements are reduced by up to 80.7% and 61.3%, respectively, when the entire depth and width of soil within basement are reinforced. Installation of isolation wall can greatly reduce tunnel movements due to adjacent basement excavation, especially for tunnel with a shallow burial depth. The effectiveness of isolation wall to reduce tunnel movement is negligible unless the wall reaches the level of tunnel invert.

• Interaction and multiscale mechanics
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• v.2 no.3
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• pp.235-261
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• 2009

This study illustrates the differences between the elasto-plastic cap model and Lade's model with Cosserat rotation through the analyses of two large-scale geosynthetic-reinforced soil (GRS) retaining wall tests that were brought to failure using a monotonically increasing surcharge pressure. The finite element analyses with Lade's model were able to reasonably simulate the large-scale plane strain laboratory tests. On average, the finite element analyses gave reasonably good agreement with the experimental results in terms of global performances and shear band occurrences. In contrast, the cap model was not able to simulate the development of shear banding in the tests. In both test simulations the cap model predicted failure loads that were substantially less than the measured ones.

• Computers and Concrete
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• v.33 no.5
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• pp.545-557
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• 2024

A real-case incident occurred where a 9-meter-high segment of a pre-fabricated concrete separation wall unexpectedly collapsed. This collapse was triggered by improperly depositing excavated soil against the wall's back, a condition for which the wall segments were not designed to withstand lateral earth pressure, leading to a flexural failure. The event's analysis, integrating technical data and observational insights, revealed that internal forces at the time of failure significantly exceeded the wall's capacity per standard design. The Lattice Discrete Particle Model (LDPM) further replicates the collapse mechanism. Our approach involved defining various parameter sets to replicate the concrete's mechanical response, consistent with the tested compressive strength. Subsequent stages included calibrating these parameters across different scales and conducting full-scale simulations. These simulations carried out with various parameter sets, were thoroughly analyzed to identify the most representative failure mechanism. We developed an equation from this analysis that quickly correlates the parameters to the wall's load-carry capacity, aligned with the simulation. Additionally, our study examined the wall's post-peak behavior, extending up to the point of collapse. This aspect of the analysis was essential for preventing failure, providing crucial time for intervention, and potentially averting a disaster. However, the reinforced concrete residual state is far from being fully understood. While it's impractical for engineers to depend on the residual state of structural elements during the design phase, comprehending this state is essential for effective response and mitigation strategies after initial failure occurs.

• Journal of the Korean Geosynthetics Society
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• v.14 no.4
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• pp.117-127
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• 2015

Recently, there has been a string of negligent accidents for the retaining wall and slope. In order to measure the ground deformation for the MSE wall, the authors carried out the model test to assess behavioral characteristics of geogrid MSE walls in active failure state with different conditions of geogrid reinforcement. The models are built in the soil container box having dimension, 100 cm long, 90 cm height, and 10 cm wide. The reinforcement used in the model test is geogrid (polyvinyl chloride, PVC). Three geogrids are sized by $30cm{\times}60cm$, $30cm{\times}70cm$, $30cm{\times}80cm$ (width ${\times}$ length) respectively. In this study, the laboratory model tests represented for several conditions of the MSE wall, and then its results were compared to 2D FE analysis.

• Journal of the Korean Geosynthetics Society
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• v.19 no.1
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• pp.75-82
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• 2020

There have been often cases of collapse for geogrid reinforced soil (GRS) retaining wall. Hence, social interest in the reinforcement and restoration of the collapsed GRS wall is increasing day by day. However, there are only few researches. For this reason, a series of numerical analyses using the Plaxis 2D program was conducted in this study to analyze the suitable reinforcement methods that can be applied on the existing damaged GRS wall caused by overturning of the modular blocks facing and the surface settlement at the backfill as the results from the design failure. The restoration plan used in this study is composed of two cases: (Case 1) soil nailing reinforcement and reinforced concrete (RC) wall facing construction on the existing damaged GRS wall; and (Case 2) removal of the entire damaged GRS wall and then reconstruction. The results on the internal stability of the GRS wall show that Case 1 obtained a greater safety factor than Case 2 for tensile force while Case 2 had a greater safety factor than Case 1 for pullout failures. Case 1 was found to be more stable than Case 2 in terms of the global slope safety by shear strength reduction method and the external deformation behavior by numerical analysis. In this study, the existing damaged GRS wall which was reinforced using Case 1 method shows more stable external behavior.

• Journal of the Korean Geosynthetics Society
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• v.16 no.4
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• pp.83-92
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• 2017

This paper deals with numerical analysis of behavior of curved mechanically stabilized earth(MSE) walls with geosynthetics reinforcement. Unlike typical concrete retaining walls, MSE wall enables securing stability of higher walls without being constrained by backfill height and is currently and widely used to create spaces for industrial and residential complexes. The design of MSE walls is carried out by checking external stability, similarly to the external checks of conventional retaining wall. In addition, internal stability check is mandatory. Typical stability check based on numerical analysis is done assuming 2-dimensional condition (plane strain condition). However, according to the former studies of 3-dimensional MSE wall, the most weakest part of a curved geosynthetic MSE wall is reported as the convex location, which is also identified from the studies of the laboratory model tests and field monitoring. In order to understand the behaviour of the convex location of the MSE wall, 2-dimensional analysis clearly reveals its limitation. Furthermore, laboratory model tests and field monitoring also have restriction in recognizing their behaviour and failure mechanism. In this study, 3-dimensional numerical analysis was performed to figure out the behaviour of the curved part of the geosynthetic reinforced wall, and the results of the straight-line and curved part in the numerical analysis were compared and analysed. In addition, the behaviour characteristics at each condition were compared by considering the overburden load and relative density of backfill.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.3 no.3
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• pp.71-86
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• 1983

Current R.C. retaining wall design is bared on WSD, but the reliability based design method is more rational than the WSD. For this reason, this study proposes a reliability based design criteria for the cantilever retaining wall, which is most common type of retaining wall, and also proposes the theoretical bases of nominal safety factors of stability analysis by introducing the reliability theory. The limit state equations of stability analysis and design of each part of cantilever retaining wall are derived and the uncertainty measuring algorithms of each equation are also derived by MFOSM using Coulomb's coefficient of the active earth pressure and Hansen's bearing capacity formula. The levels of uncertainties corresponding to these algorithms are proposed appropriate values considering our actuality. The target reliability indices (overturning: ${\beta}_0$=4.0, sliding: ${\beta}_0$=3.5, bearing capacity: [${\beta}_0$=3.0, design for flexure: [${\beta}_0$=3.0, design for shear: ${\beta}_0$=3.2) are selected as optimal values considering our practice based on the calibration with the current R.C. retaining wall design safety provisions. Load and resistance factors are measured by using the proposed uncertainties and the selected target reliability indices. Furthermore, a set of nominal safety factors, allowable stresses, and allowable shear stresses are proposed for the current WSD design provisions. It may be asserted that the proposed LRFD reliability based design criteria for the R.C. retaining wall may have to be incorporated into the current R.C. design codes as a design provision corresponding to the USD provisions of the current R.C. design code.

• Journal of the Korean Geosynthetics Society
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• v.4 no.2
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• pp.29-38
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• 2005

It is essential to take consideration of long-term deformation characteristics of mechanically stabilized earth wall user sustained and repeated loads for design and construction, especially for use as part of permanent structures. This paper presents the long-term performance of a full-scale geogrid reinforced segmental retaining wall results based on the measured strains in geogrids for three years. The results indicate that the reinforcement tensile strains tend to continuously increase after wall completion with the increase being more pronounced in the reinforcement layers in the lower tier. It can be concluded that the long-term deformation should be taken in account for walls constructed as part of permanent structures for which wall deformation should be controlled.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2000.10a
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• pp.451-457
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• 2000

A series of consolidated undrained triaxial tests for compacted short fiber reinforced clay were performed to increase the field applications, e.g. retaining wall, waste landfill, soft ground etc. of soil admixtures mixed with short fiber. Kaolin clay and three types of fiber were selected. To acquire reliable length of fibers, an auto cutter was used and a helical mixer was also used to avoid floating of fibers during mixing soil and fibers. It is found that reinforcing effect by aspect ratio and mixing ratio of short fiber decreases as confining pressure is increased. Reinforcing effect has a maximum value at the aspect ratio of 120 and the fiber content of 0.6%∼1.2% and low confining pressure like 50kPa.