• 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.

• Journal of the Korean Geotechnical Society
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• v.16 no.6
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• pp.153-160
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• 2000

본 연구는 과제하중의 재하폭과 재하위치를 매개변수로 변화시켜 옹벽의 뒤채움재 상부 지표면에서 제한폭의 과재하중작용시 그의 활동거동에 관한 실험적, 수치적 해석적 연구이다. 중력 수준을 1g, 20g,40g로 변화시켜 수행한 원심모형실험을 통해 구한 기초의 극한지지력 및 하중-침하특성, 하중-옹벽수평변위특성에 관하여 조사연구 하였다. 또한, 옹벽의 활동으로 인한 지반파괴의 영향을 받기 시작하는기초의 재하위치를 추정하기 위하여 종래의 얕은 기초의 극한지지력 실험을 수행하여 이들 결과와 함께 비교하였다. 한편, 모형실험결과와 기존의 이론식을 수정보완한 해석 결과와 비교분석하였다.

• Journal of Industrial Technology
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• v.27 no.A
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• pp.121-130
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• 2007

Centrifuge model tests were performed to find appropriate equations proposed previously of estimating the bearing capacity of the composite clayey soil reinforced with sand compaction pile. Model tests were carried out with changing the replacement ratio of SCP (20%, 40%, 70%), contents of fine materials (5%, 10%, 15%) and ratio of treated width to loading width (1B, 2B, 3B). Test results about bearing capacity of the composite ground were obtained by performing the surcharge load tests with measurements of applied loads and vertical displacement. Bearing capacities against bulging and shear failures were estimated by the existing equations. As results of comparing the estimated bearing capacity with experimental values the bearing capacities estimated by Greenwood's equation (1970) for bulging failure mode were similar to the test results.

• Journal of Industrial Technology
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• v.25 no.A
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• pp.67-73
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• 2005

In this research, centrifuge model experiments and numerical approach of finite element method to analyze experimental results were performed to investigate the behavior of improved ground with sand compaction piles. One of typical clay minerals, kaolinite powder, were prepared for soft ground in model tests. Jumunjin standard sand was used to sand compaction pile installed in the soft soil. In order to investigate the characteristics of mechanical behavior of sand compaction piles with low replacement ratios, centrifuge model experiments with the replacement ratio of 40%, changing the width of improved area with respect to testing results the width of surcharge loads, were carried out to obtain of bearing capacity, characteristics of load-settlement, vertical stresses acting on the sand pile and the soft soil failure mechanism in improved ground.

• Journal of the Korean Geotechnical Society
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• v.22 no.8
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• pp.13-24
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• 2006

A site investigation has been performed for bridge abutments constructed on soft ground, which are deformed laterally by backfill. As the result from the evaluation of lateral movement in bridge abutment, the foundation piles were not considered as the passive pile at the design stage and the period for soft ground improvement was not proper. In order to prevent lateral movement of bridge abutment, the pile slab is proposed as a countermeasure. This method can effectively prevent the lateral flow of soft ground, since the overburden surcharge due to backfill on soft ground would be effectively delivered to bedrock through the piles in soft ground. The instrumentation system is designed and installed to investigate the behavior of bridge abutment on soft ground reinforced by pile slab. The instrumentation results show that pile slab effectively resists to the lateral movement of bridge abutment due to backfill. Also, the surcharge loads due to backfill are transmitted to the bedrock through piles. It confirms that the pile slab effectively resists to the lateral movement of bridge abutment due to backfill and the applied design method is reasonable.

• Geotechnical Engineering
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• v.11 no.4
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• pp.37-48
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• 1995

The dynamic behavior of dry sand under different vibration conditions is studied through laboratory experiments. Sinusoidal and random vibration experiments of sand are carried out in vertical direction under various surcharge loads. Five different sand samples are selected for the azperiment. They are composed of four different -size samples of particles and one sample which is simulated the field condition. In case of sinusoidal vibration, the change in relative density is measured with acceleration levels. To produce an acceleration, the vibration amplitude is maintained within the range of 0.4mm~0.6mm and the vibration frequency is changed within the range of 3Hz~40Hz. In case of random vibration, the combined sinusoidal acceleration is produced by a random vibration generator and the change in relative density is measured by an accelerometer. Based on the experimental results, it is found that the sandy soil is compacted to 94%~99% of relative density by vertical acceleration and the peak acceleration producing the maximum relative density is proportional to the difference between maximum and minimum void ratios. It is also found that the effect of surcharge loading : the greater the surcharge loading, the larger the change in relative density and the greater the acceleration required to change the relative density.

• Journal of the Korean Geotechnical Society
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• v.34 no.6
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• pp.5-16
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• 2018

In this study, the large scale laboratory model tests were executed to investigate the lateral resistance characteristics of $2{\times}2$ group pile under lateral loads according to the array method and installation angle of piles. The effect on the behavior of $2{\times}2$ group pile was also investigated through model tests varying the pile diameter and length, distance to pile top from the ground surface, center-to-center (CTC) length and surcharge etc. From these test results, it was found that the lateral resistance of $2{\times}2$ group pile of which piles were constructed slantly in both directions was greater than that of group pile of which piles were constructed vertically. And as a result of parameter tests on the lateral resistance of $2{\times}2$ group pile, it was found that the most important parameter was the pile length. As the embedment depth ratio (L/D) increased to 36.5 from 26.5, the lateral resistance increased 3~4 times or more. But the center-to-center (CTC) length, distance to pile top from the ground surface and surcharge did not affect much on the lateral resistance of group pile.

• Geomechanics and Engineering
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• v.13 no.2
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• pp.255-267
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• 2017

Soft clay strata can suffer significant settlement or stability problems under building loads. Among the methods proposed to strengthen weak soils is the application of a stone masonry trench (SMT) beneath RC strip foundations (as a masonry pad-stone). Although, SMTs are frequently employed in engineering practice; however, the effectiveness of SMTs on the ultimate bearing capacity improvement of a strip footing rested on a weak clay stratum has not been investigated quantitatively, yet. Therefore, the expected increase of bearing capacity of strip footings reinforced with SMTs is of interest and needs to be evaluated. This study presents a two-dimensional numerical model using the discrete element method (DEM) to capture the ultimate load-bearing capacity of a strip footing on a soft clay reinforced with a SMT. The developed DEM model was then used to perform a parametric study to investigate the effects of SMT geometry and properties on the footing bearing capacity with and without the presence of surcharge. The dimensions of the SMTs were varied to determine the optimum trench relative depth. The study showed that inclusion of a SMT of optimum dimension in a soft clay can improve the bearing capacity of a strip footing up to a factor of 3.5.

• Proceeding of KASS Symposium
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• 2008.05a
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• pp.61-65
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• 2008

A 4-story reinforced concrete structure built above an underground parking garage shows some slab deflections, and the deflections of the concrete floor slabs are proposed to be alleviated by the application of light-weight topping material in conjunction with localized strengthening of the slabs. The application of light-weight concrete topping on the existing slab has been simulated and its performance to anticipated loads has been analyzed. The application of light-weight topping material imposes additional weight on the exiting floor slabs. This added weight on the existing slabs causes over-stressing of the slabs. This over-stressing can be alleviated by enhancing the load carrying capacity of the existing slabs. Additional load carrying capacity in the existing slabs can be developed by localized strengthening of the slabs utilizing techniques such as the application of fiber-reinforced composites on the bottom surface of the slabs, and application of fiber-reinforced composites adequately complements the capacity of the existing slabs to bear the additional load imposed by light-weight leveling material. Additional moments in the beam and columns induced by the application of the light-weight topping material were tabulated and compared with capacity. The moment D/C ratios of the beam and columns are well the range of acceptable limits, and the beam and columns are not overstressed by the application of the surcharge.

• Journal of Industrial Technology
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• v.26 no.A
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• pp.101-108
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• 2006

This study is the results of experimental and numerical study on the consolidational behavior of multi-layered soft soil ground installed with plastic board drains (PBD). Centrifuge model tests with a marine clay sampled from field were performed to investigate the consolidational behavior of multi-layered ground where a dredged soil was placed on the soft clay ground and PBDs were installed. Test results were compared with those of numerical analyses, using the 2-D equivalent model previously proposed. From test results, it was found that the amount of consolidation settlement occurred in the original ground due to embankment surcharge loads was in the range of 38% of total settlement in the whole ground. From the results of cone penetration tests executed after finishing the centrifuge model tests, the cone resistance was found to increase with depth. The measured water contents inbetween PBDs were in the ranges of 38~50% and their values tended to increase with increasing the distance between PBDs.