• Proceedings of the Korean Geotechical Society Conference
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• 2009.03a
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• pp.750-758
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• 2009

This study, as basic research which was intended to develope the surface reinforcement method using reinforcement material which is applicable to very soft ground in Korea, was aimed at proposing the design parameter for the surface ground improvement method. To that end, a wide width tensile test using geotextile, geogrid and steel bar (substitute for bamboo) and 25 kinds of the laboratory model tests with the end restraint conditions of the reinforcement that comprises the constrained and partially constrained (3 types) conditions were conducted. And the result indicated that the modulus of subgrade reaction or $N_c$ value (5.3) apparently overestimated the bearing capacity of very soft ground such as dredged ground. Moreover, as a result of model test by partially constraining the preload of 23.0kgf using geotextile, the effect of bearing capacity($q_1$) appeared to be the largest till the loading stress was $0.4tf/m^2$ due to cohesion, while it reached 75% of the maximum bearing force after $0.4tf/m^2$ due to increase in the effect of bearing capacity($q_2$) caused by the tensile force of the reinforcement. Such results tended to have appeared constantly or very similarly with each other, irrespective of the type of reinforcement (geogrid, steel bar) and constraint conditions.

• Geotechnical Engineering
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• v.12 no.5
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• pp.5-16
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• 1996

When braced excavation with temporary retaining wall installation, is performed in loose sand with high ground water level boiling may be induced and considerable damage on the excavation works and structures in the vicinity can take place. Recently, for the purpose of reinforcement of ground and cut-off of ground water behind the temporary retaining wall, high pressure jet grouting is widely used. The purpose of this paper is to investigate the effects of jet grouting on ground reinforcement and cut -off of the ground water behind temporary retaining walls for braced excavation. A series of both laboratory and field tests has been performed. The test results show that high pressure jet grouting has sufficient effects on reinforcement of stiffness of ground and retaining wall. The permeability of the improved ground was 10-f_ 10-3cm l s smaller than those of the original ground. Therefore, the effect on cut off of ground water behind temporary retaining walls could be improved by high pressure jet grouting method.

• Proceedings of the KSR Conference
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• 2004.10a
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• pp.1144-1149
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• 2004

This study deals with the damage reinforcement of structures under the ground such as gallery pipes subjected to railway loads. Railway loads with various moving velocities make significant influences on the ground gallery pipes passing through under the railway. For real structures this study analyzes such effects in detail and establishes a method for the efficient damage reinforcement Moreover we predict the hereafter structural behaviors of gallery pipes under the ground by several numerical simulation. The results of this study are expected to offer useful guidelines for explaining the complicated damage characteristics of the ground gallery pipe structures.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.03a
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• pp.338-350
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• 2010

As existing materials for ground reinforcement, chemical grout material using cementitous materials and waterglass was used. But many problems in terms of ground reinforcement effects were implicated. In this study, for development and applicability verification of new materials, viscosity, fluidity, permeability, Self-Leveling, keeping of drilled hole, antiwashout underwater, resistance of water (groundwater dilution and minimize material eluting) and the early strength and long-term strength characteristics of developed materials was confirmed, and material standards, and establishing construction standards for the various model tests were conducted. As a result, high viscosity, flowability, permeability and keeping of drilled hole characteristics are excellent, in addition to the early strength properties, dilution does nat occur to groundwater, including groundwater is available for dealing with environmental issues. Application of basic and reinforcement method by Filler function in addition to structure can also or development of a new concept can be expected. In addition, middle and large-diameter drilled shaft, micropile, ground anchors, soil-nailing, steel pipes multi-grouting reinforcement for cement injection process could be used enough to even be considered.

• Tunnel and Underground Space
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• v.25 no.3
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• pp.275-283
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• 2015

Excavation of underground space in soft ground implicate to the structure, such as subsidence. As a result, it has been acting as a serious risk to the stability of the roads and facilities. Therefore, in order to stabilize the soil stabilization and reinforcement of the structure, we have been using a number of methods and injecting material. In this study, we compared and analyzed the amount of subsidence regarding the ground reinforcement during underground excavation in soft ground by performing model test. And three-dimensional numerical analysis was performed using FLAC 3D. The subsidence was simulated numerically according to the tunnel excavation. The subsidence results of the model tests and numerical analyzes were relatively consistent. Thus comparing the ground subsidence by varying the reinforcement area on the numerical analysis was analyzed. As a results, three-dimensional numerical simulation could be regarded to simulate better on the ground subsidence by various kinds of underground excavation and it can be used as a material of subsidence prevention methods.

• Journal of the Korean Geosynthetics Society
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• v.19 no.3
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• pp.23-33
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• 2020

The lateral bearing characteristics are important factors in the case of large diameter drilled shafts and the measures to increase this are to improve the adjacent ground of the pile to increase the rigidity and to increase the rigidity of the pile itself. There are many suggestions for increasing rigidity by reinforcing casing on the pile, but few studies have been done related to this. Therefore, in this study, the lateral bearing characteristics according to casing reinforcement length were studied for each ground condition using non-linear analysis to evaluate the appropriate casing reinforcement length of the large diameter drilled shafts depending on the ground conditions. As a result, the lateral bearing characteristics of the large diameter drilled shafts are most effective if the casing reinforcement length ratio is 1.2, and depending on the ground conditions, the more loose the ground, the greater the reinforcement effect.

• Journal of the Korean Geosynthetics Society
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• v.18 no.1
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• pp.55-65
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• 2019

This paper describes results of experimental and numerical analyses, in order to analyze a reinforcement effect of concrete mat on open cut restoration of underground cavity. The plate loading tests were conducted to evaluate a reinforcement effect of concrete mat, at reinforcement depths from the ground surface of 10 cm, 20 cm, and 30 cm. The result showed that the reduction ratio of stress (earth pressure) was about 60% at all reinforcement depth. The reinforcement effect considering ground surface settlement and reduction ratio of stress based on laboratory tests and numerical analysis was significant, at reinforcement depths from the ground surface of 10 cm~20 cm. LFWD test results showed that subgrade modulus was the largest when concrete mat was installed 20 cm below ground surface. Therefore, it is effective to reinforce concrete mat within 20 cm from the surface, when the underground cavity due to damage of underground utilities was formed in the height direction to the bottom of the pavement layer.

• Journal of the Korean Geotechnical Society
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• v.34 no.12
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• pp.71-82
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• 2018

This study presents a reasonable and economical DCM reinforcement length for the various factors (the embankment height, the distance from the embankment to the underground structure, the depth of the soft ground, and the compression index and the swelling index of the soft ground) that affect the stability of the structure due to lateral movement. Based on these results, we analyzed each factor's degree of influence and figured out which factor influenced the lateral movement most. The cross section of the embankment on the soft ground was modeled by using the Finite Element Program and reinforced with DCM. The results show that the increase rate of the reinforcement length with the increase of the embankment height is about 9~50%, the increase rate of the reinforcement length with the depth of soft ground is about 13~30%, and the increase rate of the reinforcement length with increasing compression index is about 3~25%. In addition, the influence of each factor on each other was analyzed. As a result, among the separation distance, the compressive index and the maximum to minimum slope ratio of the reinforcement length of the embankment height, the separation distance was the largest for the depth of soft ground. As the depth of the soft ground increases, the ratio of the maximum to minimum slope of the reinforcement length according to the embankment height is 3.75, the ratio of the maximum to minimum slope of the reinforcement length according to the spacing distance is 4.3, and the ratio of maximum to minimum slope according to compression index is 2.5. From these results, it is confirmed that the three factors are greatly affected by the depth of soft ground.

• Proceedings of the Korean Geotechical Society Conference
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• 2001.03a
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• pp.425-432
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• 2001

Compaction Grouting System, the method which makes ground compact by injection of low slump mortar, Is widely used for reinforcement of soft ground, restoration of structures happened differential settlement, underpinning and restoration of damaged dam core. The quantitive analysis of ground improvement for this method has not performed yet. So, design parameters about thls method must be studied through performance of CGS in various types of soil to make CGS adaptable widely. In this study PBT, SPT and field density test were performed for analysis of the characteristics of ground improvement and pressuremeter and inclinometer were installed for analysis of the characteristics of compaction in adjacent ground. In this paper, denoted much effects for filled ground that increasing of the bearing capacity, confirming the displacement of adjacent ground and the effective radius of injection.

• Journal of the Korean Geosynthetics Society
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• v.9 no.4
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• pp.27-37
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• 2010

Woven geotextiles (polyester mats) reinforcement is generally used to improve traffic ability, bearing capacity, and slope stability for embankment construction on soft ground. Cases of two high-strength woven geotextiles reinforcement layers are introduced in the present paper, which has been successfully constructed for rail road embankment on soft ground. According to the case results based on the limit equilibrium analyses of slope stability, the two high-strength woven geotextiles reinforcement layers on the soft ground can substantially increase the stability of the embankment by about 25%, improve the safety factor from 0.91 to 1.14, and significantly reduce the embankment construction duration at least 2 months. Therefore, the application of high-strength woven geotextiles is found to be useful for in-situ cases having the lack of construction duration and stability, as a soft ground improvement.