• Geomechanics and Engineering
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• 제12권4호
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• pp.579-593
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• 2017

Geosynthetic reinforced soil retaining walls can be employed as railway embankments to carry large static and dynamic train loads, but very few studies can be found in the literature that investigate their dynamic behavior under simulated wheel loading. A large-scale dynamic test on a reinforced soil railway embankment was therefore carried out. The model embankment was 1.65 meter high and designed to have a soilbag facing. It was reinforced with HDPE geogrid layers at a vertical spacing of 0.3 m and a length of 2 m. The dynamic test consisted of 1.2 million cycles of harmonic dynamic loading with three different load levels and four different exciting frequencies. Before the dynamic loading test, a static test was also carried out to understand the general behavior of the embankment behavior. The study indicated the importance of loading frequency on the dynamic response of reinforced soil railway embankment. It also showed that toe resistance played a significant role in the dynamic behavior of the embankment. Some limitations of the test were also discussed.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 추계학술대회 논문집
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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.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 추계학술대회 논문집
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• pp.905-917
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• 2008

Road or Railway construction over soft ground is needed to be considered on secondary consolidation which will be caused differential settlement, lack of transport serviceability, higher maintenance cost. Especially for the railway construction in the second phase of Gyung-Bu or Ho-Nam high speed railway, concrete slab track has been adapted as a safe and cost effective geotechnical solution. In this case controlling the total settlement under the tolerance is essential. And pile supported geogrid reinforced construction method is suggested as a solution for the problem of the traditional method on soft soil treatments. Pile supported geogrid reinforced construction method consists of piles that are designed to transfer the load of the embankment through the compressible soil layer to a firm foundation. The load from the embankment must be effectively transferred to the piles to prevent punching of the piles through the embankment fill creating differential settlement at the surface of the embankment. The arrangement of the piles can create soil arching to carry the load of embankment to the piles. In order to minimize the number of piles geogrid reinforced pile supported construction method is being used on a regular basis. This method consists of one or more layers of geogrid reinforcement placed between the top of the piles and the bottom of the embankment. This paper presents several methods of pile supported geogrid reinforced construction and calculation results from the several methods and comparison of them.

• Structural Engineering and Mechanics
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• 제56권4호
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• pp.507-534
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• 2015

The present work investigates the behavior of the embankment models resting on soft soil reinforced with ordinary and stone columns encased with geogrid. Model tests were performed with different spacing distances between stone columns and two lengths to diameter ratios (L/d) of the stone columns, in addition to different embankment heights. A total number of 42 model tests were carried out on a soil with undrianed shear strength $${\sim_\sim}10kPa$$. The models consist of stone columns embankment at s/d equal to 2.5, 3 and 4 with L/d ratio equal 5 and 8. Three embankment heights; 200 mm, 250 mm and 300 mm were tested for both tests of ordinary (OSC) and geogrid encased stone columns (ESC). Three earth pressure cells were used to measure directly the vertical effective stress on column at the top of the middle stone column under the center line of embankment and on the edge stone column for all models while the third cell was placed at the base of embankment between two columns to measure the vertical effective stress in soft soil directly. The performance of stone columns embankments relies upon the ability of the granular embankment material to arch over the 'gaps' between the stone columns spacing. The results showed that the ratio of the embankment height to the clear spacing between columns (h/s-d) is a key parameter. It is found that (h/s-d)<1.2 and 1.4 for OSC and ESC, respectively; (h is the embankment height, s is the spacing between columns and d is the diameter of stone columns), no effect of arching is pronounced, the settlement at the surface of the embankment is very large, and the stress acting on the subsoil is virtually unmodified from the nominal overburden stress. When $(h/s-d){\geq}2.2$ for OSC and ESC respectively, full arching will occur and minimum stress on subsoil between stone columns will act, so the range of critical embankment height will be 1.2 (h/sd) to 2.2 (h/s-d) for both OSC and ESC models.

• 한국철도학회논문집
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• 제9권6호
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• pp.753-760
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• 2006

This paper presents the procedure and results of the numerical modelling that was carried out to investigate the stability of reinforced soil slopes under dynamic railway load. The two-dimensional explicit dynamic finite element method (ABACUS) was used to carry out the numerical analyses. To simulate the railway load, the top surface of the embankment was excited by the uniform distributed load whose frequency and magnitude was estimated by the measured railway acceleration during train passing. The embankment displacements and geogrid axial forces were analyzed to evaluate the stability of reinforced soil slopes under the dynamic train load.

• 대한토목학회논문집
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• 제28권2C호
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• pp.133-141
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• 2008

토목섬유보강 성토지지말뚝시스템에서 지반아칭에 의한 하중전이 특성을 규명할 수 있는 이론해석법을 개발하였다. 이론해석 결과, 성토지지말뚝에 토목섬유가 복합시공되면, 말뚝의 효율이 증가하였으며, 효율의 증대효과는 지반아치가 완전히 발달하기 이전인 저성토 구간에서 특히 두드러지게 나타났다. 또한, 이론해석법에 의한 하중전이는 말뚝의 간격, 성토고, 지반정수 및 토목섬유에 크게 영향을 받고 있다. 즉, 말뚝의 간격이 증가하면 말뚝의 효율은 감소하며, 성토고, 성토지반의 내부마찰각 및 토목섬유의 강도가 증가하면 효율이 커지게 된다. 이와같은 해석결과는 본 제안식이 토목섬유보강 성토지지말뚝시스템에서의 지반아칭효과를 잘 설명해주는 합리적인 해석법임을 나타내고 있다.

• Geomechanics and Engineering
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• 제33권4호
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• pp.353-367
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• 2023

The construction of a protective embankment is a suitable strategy to stop and control high-energy rock blocks' impacts during the rockfall phenomenon. In this paper, based on the discrete element numerical method, by modeling an existing embankment reinforced with geogrid, its stability status under the impact of a rock block with two types of low and high kinetic energy, namely 2402 and 4180 kJ, respectively, has been investigated. The modeling results show that the use of geogrid has caused the displacement in the front and back of the embankment to decrease by more than 30%. In this case, the reinforced embankment has stopped the rock block earlier. The displacements obtained from the DEM modeling are compared with the displacements measured from an actual practical experiment to evaluate the results' validity. Comparison between the results shows that the displacement values are close together, while the maximum percentage error in previous studies by an analytical method and the finite element method was 76.4% and 36.6%, respectively. Therefore, the obtained results indicate the discrete numerical method's high ability compared to other numerical and analytical methods to simulate and design the geogrid-reinforced soil embankment under natural disasters such as rockfall with a minor error.

• 한국지반공학회논문집
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• 제32권6호
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• pp.5-16
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• 2016

성토지지말뚝공법에서 연약지반 강성, 성토체의 내부마찰각, 토목섬유의 인장강성, 성토고의 변화가 한계높이로 표현되는 하중 전이 흙 아치의 형태에 어떠한 영향을 미치는지 수치해석적으로 분석하였다. 매개변수 해석결과에서 연약지반 강성이 한계높이에 가장 큰 영향을 미쳤다. 주 영향요소인 연약지반 강성과 다른 매개변수의 조합에 대해 한계높이가 어떻게 변화하는지 등고선도 형태의 도표를 제시하고 분석하였다. 해석 결과는 연약지반 강성과 성토고의 조합에 대해 한계높이가 매우 민감하게 변함을 보였다. 연약지반 강성이 충분히 낮은 조건에서 성토체의 내부마찰각에 대해 한계높이가 민감하게 변하였다. 토목섬유가 포설된 조건에서는 토목섬유 인장강성의 변화가 한계높이 변화에 큰 영향을 주지 않았다.

• Geomechanics and Engineering
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• 제5권4호
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• pp.313-329
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• 2013

Vetiver grass (Vetiveria zizanioides) is being effectively used in many countries to protect embankment and slopes for their characteristics of having long and strong roots. In this paper, in-situ shear tests of the ground with the vetiver roots have been conducted to investigate the stabilization properties corresponding to the embankment slopes. Numerical analyses have also been performed with the finite element method using elastoplastic subloading $t_{ij}$ model, which can simulate typical soil behavior. It is revealed from field tests that the shear strength of vetiver rooted soil matrix is higher than that of the unreinforced soil. The reinforced soil with vetiver root also shows ductile behavior. The numerical analyses capture well the results of the in-situ shear tests. Effectiveness of vetiver root in geotechnical structures-strip foundation and embankment slope has been evaluated by finite element analyses. It is found that the reinforcement with vetiver root enhances the bearing capacities of the grounds and stabilizes the embankment slopes.

• 한국지반신소재학회논문집
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• 제9권3호
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• pp.9-18
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• 2010

토목섬유보강 성토지지말뚝시스템에서의 하중전이 특성을 규명하기 위하여 일련의 모형실험을 실시하였다. 모형토조에 단독캡 말뚝을 설치하고, 토목섬유를 포설한 후 성토를 실시하였다. 연약지반 대체재료로서 스펀지고무를 사용하였다. 실험결과 성토지지말뚝시스템의 효율은 일정한 말뚝간격비에서는 성토고가 증가할수록 비선형적으로 증가하여 이후 일정한 값에 수렴하는 경향을 나타내었다. 또한 성토고가 일정한 조건에서는 말뚝간격비가 증가할수록 효율의 크기는 감소하였다. 토목섬유를 보강한 경우, 무보강시와 비교하여 말뚝으로 전이되는 하중이 증가하는 것으로 나타났다. 이는 토목섬유의 보강이 연약지반의 거동을 억지하는데 효과가 있음을 나타내는 것이다. 결국 토목섬유보강 성토지지말뚝시스템에서의 하중전이 특성은 말뚝캡 설치간격, 성토고, 지반의 강도정수 및 토목섬유 강성 등에 복합적으로 영향을 받음을 알 수 있다.