• International Journal of Railway
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• v.6 no.3
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• pp.107-111
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• 2013

In order to constrain the railway roadbed settlement which causes track irregularity, and thus threats running stability and ride quality, advanced Back-to-Back (BTB) reinforced retaining wall was numerically analyzed as railway roadbed structure. This study is intended to improve conventional Back-to-Back reinforced retaining wall as the technology which would reduce the roadbed settlement in a way of constraining the lateral displacement of its prestressed vertical facing and inducing arching effects in roadbed (backfill) placed between masonry diaphragm wall and vertical facing. As a result of numerical analysis, it was found that the roadbed settlement was reduced by 10% due to the prestressed vertical facing and embedded masonry diaphragm wall of the advanced Back-to-Back reinforced retaining wall system.

• Journal of the Korean Geotechnical Society
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• v.25 no.12
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• pp.131-142
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• 2009

Geosynthetic reinforced soil walls are well recognized alternatives to conventional retaining walls due to many advantages in terms of ease of construction, economy, and aesthetics, among others. In recent years, the use of back-to-back (BTB) geosynthetic reinforced soil walls has been increasing for roadway and railway construction. However, there are insufficient studies concerning the behavior of BTB type geosynthetic reinforced soil walls. In this study a series of finite element analysis were performed for BTB walls with various wall geometry and reinforcement distribution. The results were then analyzed to relate the wall geometry and reinforcement distribution and the performance of BTB walls. Optimum reinforcement pattern was also investigated.

• Journal of the Korean Geotechnical Society
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• v.24 no.12
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• pp.41-52
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• 2008

This paper concerns the load carrying capacity of back-to-back reinforced soil wall for use in roadway and railway construction. Two test conditions, designed with due consideration of the FHW A design guideline, were first developed and a number of cases having different reinforcement lengths were tested under a surchage loading until failure. The results indicated that for cases in which two sides of reinforcements do not overlap, the wall behavior was similar to those of single wall. For cases in which the reinforcements overlap each other, on the other hand, the load carrying capacity of the wall significantly decreased when reinforced with reinforcement layers having lengths less than 50% of the wall height.

• Computers and Concrete
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• v.31 no.4
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• pp.307-314
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• 2023

In this paper we back-analyze a failure event of a 9 m high concrete cantilever wall subjected to earth loading. Granular soil was deposited into the space between the wall and a nearby rock slope. The wall segments were not designed to carry lateral earth loading and collapsed due to excessive bending. As many geotechnical programs rely on the Mohr-Coulomb (MC) criterion for elastoplastic analysis, it is useful to apply this failure criterion to the concrete material. Accordingly, the back-analysis is aimed to search for the suitable MC parameters of the concrete. For this study, we propose a methodology for accelerating the back-analysis task by automating the numerical modeling procedure and applying a machine-learning (ML) analysis on FE model results. Through this analysis it is found that the residual cohesion and friction angle have a highly significant impact on model results. Compared to traditional back-analysis studies where good agreement between model and reality are deemed successful based on a limited number of models, the current ML analysis demonstrate that a range of possible combinations of parameters can yield similar results. The proposed methodology can be modified for similar calibration and back-analysis tasks.

• Journal of the Korean Geotechnical Society
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• v.36 no.12
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• pp.69-76
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• 2020

Since the mechanically stabilized earth walls have a form of retaining wall compatible with a narrow section, the geogrid overlaps according to the separation distance between the walls. There is a problem that the overall behavior may occur in the state of being integrated with the stress change due to the interaction of the geogrid. Therefore, a careful approach is required at the design stage, but there are currently no design criteria or guidelines in Korea. This study investigated the optimal reinforcement length ratio according to the retaining wall width to height ratio (width to height ratio, Wb/H) for these back-to-back mechanically stabilized earth walls. Retaining wall width ratio is 1.1H, 1.4H, 1.7H, 2.0H for Case II of the FHWA design standard, and the height is 3.0 m, 5.0 m, 7.0 m, and 10.0 m, which are most commonly applied. Through numerical analysis, the appropriateness of the FHWA design standard and the optimal reinforcement length ratio according to the height of the retaining wall and the width of the retaining wall were proposed.

• Journal of the Korean Geotechnical Society
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• v.32 no.2
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• pp.43-52
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• 2016

Assembled Earth Retaining wall (AER-wall is used here) using back pile (back supporting beam is used from here) has been developed at Pusan National University. Both cost and time have been significantly reduced because AER-wall can be fabricated in a shop. Also its stability has been improved with a back supporting beam reducing earth pressure. In this study, the test results were analyzed after laboratory model tests were performed. The lateral displacement of AER-wall significantly decreased with both inclined wall and back supporting beams. As a result, the stability of AER-wall and effect of back supporting beam have been analyzed and verified.

• Journal of the Korean Geosynthetics Society
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• v.10 no.2
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• pp.55-66
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• 2011

This paper presents the results of an investigation on the failure mechanism of geosynthetic reinforced soil walls in back-to-back configuration using 1-g reduced-scale model tests as well as discrete element method-based numerical investigation. In the 1-g reduced scale model tests, 1/10 scale back-to-back walls were constructed so that the wall can be brought to failure by its own weight and the effect of reinforcement length on the failure mechanism was investigated. In addition, a validated discrete element method-based numerical model was used to further investigate the failure mechanism of back-to-back walls with different boundary conditions. The results were then compared with the failure mechanisms defined in the FHWA design guideline.

• Journal of the Korean Geotechnical Society
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• v.18 no.1
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• pp.71-78
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• 2002

This paper presents a back-calculation technique leer the prediction of the behavior of earth wall inserted in multi-layered soil deposit. The soil properties are back-calculated from the measured displacement at each construction stage and the behavior of earth wall far the next construction stage is predicted using back-calculated soil properties. For multi-layered soil deposit, the back-calculation would be very difficult due to the increase in the number of variables. In this study, to solve this difficulty, the back-calculation was performed successively from the lowest layer to the upper layers. An efficient elasto-plastic beam-column analysis was used for forward analysis to minimize the computation time of iterative back-calculation procedure. The coefficients of subgrade reaction and lateral earth pressure necessary for the formation of p-y curve were selected as back calculation variables, and to minimize the effect of abnormal behavior of the wall which might be caused by any unexpected action during construction, the difference between measured displacement increment and computed displacement increment at each construction stages is used as the objective function of optimization. The constrained sequential linear programming was used for the optimization technique to found values of variables minimizing the objective function. The proposed method in this study was verified using numerically generated data and measured field data.

• Journal of the Korean Society of Industry Convergence
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• v.14 no.3
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• pp.87-93
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• 2011

When applying back panel(this material is aluminum complex panel coated with fire resistance substances) for curtain wall, solar radiation and heat storage of indoor air occurs to result in thermal warpage for back panel. The purpose of this analysis is to find out the cause of thermal warpage and come up with a solution to prevent changes of back panel and reduce elements that bring negative visual elements. Also to solve this problem analyse that case to reduce heat transfer by inserting additional material and cases to increase air space distance.

• Journal of the Korean Society of Physical Medicine
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• v.16 no.4
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• pp.139-151
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• 2021

PURPOSE: This study examined the effects of wall-squat with short-foot exercise on pain, dysfunction, and pelvic alignment in chronic low back pain patients. METHODS: Thirty outpatients diagnosed with chronic low back pain and pronated foot were enrolled in this study. The patients were divided randomly into a wall-squat with short-foot exercise group (WS; n = 15) and a normal wall-squat exercise group (NW; n = 15). These groups performed their respective exercises 15 times, for three sets, three times a week over six weeks. The visual analogue scale (VAS) was used to measure the subjects' pain, and the Roland-Morris disability questionnaire (RMDQ) was used to measure the subjects' dysfunction. A navicular drop test (NDT) was used to measure the subjects' arch height. To assess the patients' pelvic alignment, their lordosis, sacral tilt, lumbar width, sacral width, ilium length, and ilium width were measured by X-ray imaging. RESULTS: Both the WS and NW groups exhibited significant decreases in their VAS and RMDQ scores after exercise (p < .05). The WS group exhibited significant increases in their arch height (p < .05). Significant differences in the VAS, sacral tilt, sacral width, and ilium length were observed between the WS and NW groups (p < .05). CONCLUSION: These results suggest that wall-squat exercise is effective in decreasing the level of pain and dysfunction in chronic low back pain patients. In addition, the wall-squat with short-foot exercise is considered more effective in improving the pelvic alignment than without short-foot exercise. This can be an effective method for the non-pharmacological and non-surgical treatment of chronic low back pain