• Journal of the Korean Geosynthetics Society
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• v.11 no.4
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• pp.37-44
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• 2012

This paper describes large scale pullout test results, in order to evaluate extensibility effect of strip-type reinforcement. The same test for ribbed steel strip reinforcement also is conducted to compare the friction resistance reinforcements' evaluation results. The pullout resistance of the ribbed steel strip reinforcement, which has a small cross sectional areas, was better than the friction resistance reinforcements' due to the bearing (passive) resistance. In case of friction resistance reinforcements, the pullout resistance of extensible reinforcement was better than inextensible reinforcement' even though they have a similar cross sectional areas.

• Journal of the Korean Geosynthetics Society
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• v.6 no.3
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• pp.17-23
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• 2007

To construct an ideal geosynthetic reinforced soil retaining wall (GRS-RW), the facing of the wall should be flexible enough to accommodate a large deformation of the supporting ground and to develop the large tensile force in reinforcements during wall construction as long as the stability is ensured, but should be rigid enough to be stiff and stable as well as durable and aesthetically acceptable for a long life time when the wall is in service. Facing conditions during the construction and service of the wall are quite different. So it is difficult to be satisfied all these conditions with the current construction method which is mainly used in reinforced wall construction in Korea. Most of this contradiction could be solved by the staged construction procedure. According to the results of cases and references analyses, stage construction procedures make it possible to accommodate large deformation of the supporting ground and backfill without losing the stability of the wall, and to derive the tensile strength of reinforcement causing deformation of the facing. When the facing is a full-height rigid one, it also appeared almost impossible to occur a local shear failure of the active zone, and pull-out failure of reinforcements. Therefore, GRS-RWs having a full-height rigid facing have been constructed by the staged construction procedures that matched well with the theory of reinforced soil, which had outstanding stability and durability, and thus could be used for railways and bridge abutments in Korea in the future.

• Geomechanics and Engineering
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• v.3 no.4
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• pp.291-321
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• 2011

The paper describes a simple numerical FLAC model that was developed to simulate the dynamic response of two instrumented reduced-scale model reinforced soil walls constructed on a 1-g shaking table. The models were 1 m high by 1.4 m wide by 2.4 m long and were constructed with a uniform size sand backfill, a polymeric geogrid reinforcement material with appropriately scaled stiffness, and a structural full-height rigid panel facing. The wall toe was constructed to simulate a perfectly hinged toe (i.e. toe allowed to rotate only) in one model and an idealized sliding toe (i.e. toe allowed to rotate and slide horizontally) in the other. Physical and numerical models were subjected to the same stepped amplitude sinusoidal base acceleration record. The material properties of the component materials (e.g. backfill and reinforcement) were determined from independent laboratory testing (reinforcement) and by back-fitting results of a numerical FLAC model for direct shear box testing to the corresponding physical test results. A simple elastic-plastic model with Mohr-Coulomb failure criterion for the sand was judged to give satisfactory agreement with measured wall results. The numerical results are also compared to closed-form solutions for reinforcement loads. In most cases predicted and closed-form solutions fall within the accuracy of measured loads based on ${\pm}1$ standard deviation applied to physical measurements. The paper summarizes important lessons learned and implications to the seismic design and performance of geosynthetic reinforced soil walls.

• Journal of the Korean Geotechnical Society
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• v.21 no.8
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• pp.107-116
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• 2005

Generally, when the stability of the geosynthetic reinforced soil slopes is analyzed, the required tensile forces of each reinforcement layers are calculated from total reinforcement forces which are necessary to retain the equilibrium state of slip mass in which the slip surfaces are assumed to be a linear or bilinear. It is assumed that the reinforcement forces are increased or constant with depth. However, according to the instrumented field data and laboratory model test results, the maximum tensile strain of reinforcement in a reinforced soil slope is developed in a certain elevation, not a bottom of the slope. In the concept of reinforced soil, postulated failure surfaces are the traces of the position in which the reinforcement tensile forces are maximum in the layer, and the reinforcement tensile forces are related to the stress state on the postulated failure surface. Therefore, in this study, based on the distribution of normal stress on the slip surface, a new method for the evaluation of required tensile forces is suggested and a number of the instrumented field data are analyzed by newly suggested method. As a result, it is shown that the newly suggested method produces relatively accurate reinforcement tension forces.

• Geomechanics and Engineering
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• v.5 no.3
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• pp.263-281
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• 2013

Geotextiles and geogrids have been in use for several decades in variety of geo-structure applications including foundation of embankments, retaining walls, pavements. Geocells is one such variant in geosynthetic reinforcement of recent years, which provides a three dimensional confinement to the infill material. Although extensive research has been carried on geocell reinforced sand, clay and layered soil subgrades, limited research has been reported on the aggregates/ballast reinforced with geocells. This paper presents the behavior of a railway sleeper subjected to monotonic loading on geocell reinforced aggregates, of size ranging from 20 to 75 mm, overlying soft clay subgrades. Series of tests were conducted in a steel test tank of dimensions $700mm{\times}300mm{\times}700mm$. In addition to the laboratory model tests, numerical simulations were performed using a finite difference code to predict the behavior of geocell reinforced ballast. The results from numerical simulations were compared with the experimental data. The numerical and experimental results manifested the importance that the geocell reinforcement has a significant effect on the ballast behaviour. The results depicted that the stiffness of underlying soft clay subgrade has a significant influence on the behavior of the geocell-aggregate composite material in redistributing the loading system.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.196-203
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• 2008

Durability of geosynthetics for soil reinforcement is accounted for creep and creep rupture, installation damage and weathering, chemical and biological degradation. Among these, the long-term creep properties have been considered as the most important factors which are directly related to the failure of geosynthetic-reinforced soil(GRS). However, the creep test methods and strain limits are too various to compare the test results with each other. The most widely used test methods are conventional creep test, time-temperature superposition and stepped isothermal method as accelerated creep tests. Recently developed design guidelines recommend that creep-rupture curve be used to determine the creep reduction factor($RF_{CR}$) which is a conservative approach. In this study, the different creep test methods were compared and the creep reduction factors were estimated at different creep strain limits of 10% of total creep strain and creep rupture. In order to minimize the impact of creep strain to the GRS structures, the various creep reduction factors using different creep test methods should be investigated and then the most appropriated one should be selected for incorporating into the design.

• Geotechnical Engineering
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• v.10 no.4
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• pp.133-152
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• 1994

In the present study, an economic design of Anchored Geosynthetic(AG) System applied mainly to reinforce unstable soil slopes is investigated. For this purpose methods of stability analysis are developed to determine the optimum installation angle, required minimum length and maximum spacing of nails. Anchorage of nails within the soil mass is achieved by frictional resistance to pull out along the effective length of the nails. Cases of infinite slope and finite slope are dealt with individually. Silce methods of stability analysis developed in the present study are limit-equilibrium-based. For the case of finite slope Spencer method which considers interslice force is modified to evalyate the overall stability. In addition, the effects of various design parameters on requried length and spacing of nails corresponding to the optimum orientation of nails are analyzed. Based on the analysis, a simplified equation is given for the optimum nail orientation. Also the importance of optimum nail orientation is illustrated throughout design example, and the appropriateness of judgment criterion are examined.

• Proceedings of the Korean Fiber Society Conference
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• 2003.10b
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• pp.305-306
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• 2003

In the case of the geosynthetics usage to soil structure, there are some damages by compaction. And these damages by the installation compaction result in the unexpected changes of short and long term properties of the structure. So in the case of index test, there are some problems to the exact evaluation on the installation damage. Therefore, to the more definite evaluation on the installation damage of geosynthetics, the real site installation damage test is encouraged. (omitted)

• Journal of the Korean Geotechnical Society
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• v.20 no.1
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• pp.13-19
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• 2004

The major distress types in the domestic asphalt pavement are fatigue cracking, reflection cracking, thermal cracking, and rutting. To decrease the pavement distress by reinforcing asphalt pavement with reinforcement interlayer in geosynthetics to the traditional pavement systems can improve these problems. This study conducted laboratory test with asphalt pavement reinforced by glass fiber sheet to fix systematically geosynthetic asphalt pavement system. Laboratory tests like wheel tracking test and crack resistance test are conducted to analyze the controlling effect of glass fiber sheet on cracking and rutting of asphalt pavement.

• 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.