• Proceedings of the KSR Conference
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• 2009.05a
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• pp.1519-1524
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• 2009

Construction of high-speed concrete track embankments over soft ground needs many of the ground improvement techniques. Drains, surcharge loading, and geosynthetic reinforcement, have all been used to solve the settlement and embankment stability issues associated with construction on soft soils. However, when time constraints are critical to the success of the project, another measures should be considered. Especially, since the design criteria of residual settlement is limited as 30mm for concrete track embankment, it is very difficult to satisfy this allowable settlement by using the former construction method. Pile net method consist of vertical columns that are designed to transfer the load of the embankment through the soft compressible soil layer to a firm foundation and one or more layers of geosynthetic reinforcement placed between the top of the columns and the bottom of the embankment. In this paper, three cases with different embankment height and number of geosynthetic reinforcement, were studied through FEM analysis for efficient use of pile net method.

• Interaction and multiscale mechanics
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• v.5 no.4
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• pp.369-383
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• 2012

In this paper, soil-structure interaction analysis has been presented for beams resting on multilayered geosynthetic-reinforced granular fill-soft soil system. The soft soil and geosynthetic reinforcements are idealized as nonlinear springs and elastic membranes, respectively. The governing differential equations are solved by finite difference technique and the results are presented in non-dimensional form. It is observed from the study that use of geosynthetic reinforcement is not very effective for maximum settlement reduction in case of very rigid beam. Similarly the reinforcements are not effective for shear force reduction if the granular fill has very high shear modulus value. However, multilayered reinforced system is very effective for bending moment and differential settlement reduction.

• Journal of the Korean Society for Railway
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• v.12 no.2
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• pp.276-284
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• 2009

Recently pile-supported embankments have emerged as an optimum method when the rapid construction and strict deformation of structures are required on soft soils. Especially geosynthetic-reinforced and pile-supported (GRPS) embankments are used worldwide as they can provide economic and effective solutions. However the load transfer mechanism in GRPS embankments is very complex, and not yet fully understood. Particularly the purpose and effect of geosynthetic inclusion are ambiguous and considered as an auxiliary measure assisting the arching effect of piles. Numerical parametric study using 3D finite element method has been conducted to investigate the effect of geosynthetic reinforcement on the load transfer mechanism of GRPS embankments. Numerical results suggested that as more stiffer geosynthetic is included, arching effect decreases considerably and the load concentration to the piles mostly caused by tension effect of geosynthetic. This finding is contradictory to the common understanding that geosynthetic inclusion only enhance the efficiency of load transfer. Consequently the design parameters determined from the numerical analyses are compared with those of three existing design methods. The problems of the existing methods are discussed.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.1580-1587
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• 2005

To calculate the long-term allowable strength of geosynthetic reinforcement, replacement method was recommended. The isochronous creep curve by S. Turner was used to define the relation between creep strain and allowable strength. In isochronous curve at given time, one can read the allowable strength at allowable creep strain. The allowable strain gets from specification by directors or manufacturers according to the allowable displacement of reinforced structures. The allowable strength can be determined in relation to the allowable horizontal displacement each structures case by case. The effect of install damage on isochronous behaviors of geosynthetic reinforcement was little. In previous study, install damage increase the creep strain slightly. And the degradation was not identified. But it is supposed that degradation increase the creep strain. In conclusion, The recommended model to determine long-term allowable strength of geosynthetic reinforcements considering tensile deformation of reinforcement and soil is fit for proper, correct and economic design for reinforced earth walls.

• Journal of the Korean Geotechnical Society
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• v.27 no.1
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• pp.65-76
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• 2011

This paper presents the results of a numerical investigation on the long-term behavior of geosynthetic reinforced soil abutment. The investigation was carried out aiming at identifying the governing mechanisms of the long-term deformation of geosynthetic-reinforced soil abutment subjected to sustained loads during service life. A numerical modeling strategy was first established using the Singh-Mitchell creep model and the power law model, respectively, for the backfill and the geosyntehtic reinforcement. A parametric study on the creep properties of the backfill and the geosynthetic reinforcement was then conducted. The results indicated that a geosynthetic reinforced soil structure backfilled with marginal soil may exhibit substantial long-term deformation due to the creep effects caused by both the backfill soil and the geosynthetic reinforcement, the magnitude of which depends largely on the creep properties. This paper highlights the importance of considering the creep effect on load supporting geosynthetic reinforced soil structures when the long-term serviceability requirement is of prime importance.

• Proceedings of the KSR Conference
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• 2008.11b
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• pp.918-927
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• 2008

The problems associated with constructing high-speed concrete track embankments over soft compressible soil has lead to the development and/or extensive use of many of the ground improvement techniques used today. Drains, surcharge loading, and geosynthetic reinforcement, have all been used to solve the settlement and embankment stability issues associated with construction on soft soils. Geosynthetic-reinforced embankment supporting piles method consist of vertical columns that are designed to transfer the load of the embankment through the soft compressible soil layer to a firm foundation and one or more layers of geosynthetic reinforcement placed between the top of the columns and the bottom of the embankment. In the paper, the evaluations of a seismic performance of geosynthetic-reinforced embankment piles for a ultra soft ground during earthquake were studied. the equivalent linear analysis was performed by SHAKE for soft ground. A seismic performance analysis of Piles was performed by GROUP PILE and PLAXIS for geosynthetic-reinforced embankment piles. Guidelines is required for pile displacement during earthquake. Conclusions of the studies come up with a idea for soil stiffness, conditions of pile cap, pile length and span.

• Geomechanics and Engineering
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• v.2 no.3
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• pp.161-176
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• 2010

Discrete Element Method (DEM) simulations were developed to investigate the effectiveness of geosynthetic reinforcement and the effectiveness of maintenance techniques performed on a simulated ballast bed subjected to dynamic loading. The results from four samples subjected each one to a total of 425 load cycles are presented: one unreinforced and unmaintained sample, one unmaintained but reinforced sample, one unreinforced sample subjected to maintenance in the form of stoneblowing after 200 load cycles, and one unreinforced sample subjected to maintenance in the form of tamping after 200 load cycles. The obtained values of permanent deformation as a function of the applied number of load cycles for the four cases are presented together allowing a comparison of the effectiveness of each technique. Moreover, snapshots of the simulated track sections are presented at different moments of the simulations. The simulations indicated that the geosynthetic reinforcement may not be beneficial for the analyzed case while stoneblowing was the most effective maintenance technique.

• Journal of the Korean Geotechnical Society
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• v.19 no.6
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• pp.379-385
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• 2003

In the existing method to design geosynthetic reinforced embankment, the required strength of reinforcements is determined by vertical stress only rather than strain. This strength is not in accord with tensile strength that behaves as reinforcement in earth structures. The reinforcement and adjacent soil on the failure plan behave in one unit at the initial stress phase but they make a gap in strain as stress increases. This issue may cause a big impact as a critical factor on geosynthetic reinforcement design in earth structures. The quantitative analysis on strain behavior was performed with a PET Mat reinforced embankment on soft ground. From this study, several outstanding discussions are found that tensile strength of reinforcement governs the failure of embankment when the soil stress is greater than failure stress. Also the optimum required tensile strength of geosynthetic reinforcement(Tos) should be determined by stress, displacement, displacement gap and safety factor of soil-PET Mat at the location of PET Mat.

• Journal of the Korean Geosynthetics Society
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• v.17 no.4
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• pp.213-224
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• 2018

In this study, a series of accelerated creep tests (SIM) was carried out on geosynthetic strip reinforcements with folding grooves having different tensile strengths (15 kN, 25 kN, 35 kN, 50 kN, 70 kN, and 90 kN) to analyze creep characteristics and to assess creep reduction factors. In particular, long-term creep tests were conducted on geosynthetic strip reinforcements with 25 kN tensile strength, which is widely used, to compare and analyze the accelerated creep test results. As a result, the creep reduction factor increased with an increasing design life of reinforcement. In addition, geosynthetic strip reinforcement using the same material and manufacturing method showed similar creep reduction factors at the same design life for different tensile strengths. When both long-term and accelerated creep test data were used, the creep reduction factors from the accelerated test were estimated to be 5.9%~7.1% less than those from the long-term creep test for the design life ranging from 50 to 100 years.

• 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.