• Journal of Industrial Technology
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• v.29 no.B
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• pp.73-80
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• 2009

This paper is to investigate effect of B.G.I (Best Grouting Innovation) method on reinforcing ground. In this thesis, extensive literature review was performed to summarize theoretical backgrounds of grouting and to compare the applicability of different grouting methods. Unconfined compression test with specimen prepared by injecting different grouts of B.G.I, S.G.R and L.W methods and by changing the curing time were carried out to figure out characteristics of initial unconfined compression strength mobilized in the early stage. As results of test, the compression strength increases with curing times and specimen prepared with grouts of B.G.I method show greater values than others. On the other hands, the measured values of pH are in the range of 7-10 during tests. In field, preliminary construction to main construction at several sites were performed to confirm the effect of reinforcing the ground by application of B.G.I method. From the results of permeability test in field, SPT test and phenol reaction test, it was found that N values after grouting are greater than those before grouting and values of permeability in grouted ground is reduced significantly.

• Geomechanics and Engineering
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• v.37 no.5
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• pp.511-525
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• 2024

Micropiled raft has been used to support the existing and new structures or to provide the seismic reinforcement of foundation systems. Recently, research on micropile or micropiled raft has been actively conducted as the usage of micropile has increased, and the reinforcement effect of pile for the raft, the pile installation methods, and methods for calculating the bearing capacity of micropiled raft have been proposed. In addition, existing research results show that the behavior of this foundation system is different depending on the pile conditions and can be greatly influenced by the characteristics of the upper or lower ground depending on the conditions of pile. In other words, considering that the micropile is a friction pile, it can be predicted that the reinforcing effect of micropile for the raft and the bearing capacity of micropiled raft may depend on the cohesion of upper soil layer depending on the pile conditions. However, existing studies have limitations in that they were conducted without taking this into account. However, existing studies have limitations as they have been conducted without considering these characteristics. Accordingly, this study investigated the reinforcing effect of micropile and the bearing characteristics of micropiled raft by varying the cohesion of upper soil layer and the stiffness of pile which affect the behavior of micropiled raft. In this results, the reinforcing effect of micropile on the raft also increased as the cohesion of soil layer increased, but the reinforcing effect of pile was more effective in ground conditions with decreased the cohesion. In addition, the relationship between the axial stiffness of micropile and the bearing capacity of micropiled raft was found to be a logarithmic linear relationship. It was found that the reinforcing effect of micropile can increase the bearing capacity of raft by 1.33~ 3.72 times depending on the cohesion of soil layer and the rigidity of pile.

• Proceedings of the Korean Geotechical Society Conference
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• 1999.10a
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• pp.185-192
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• 1999

This paper presents the results of a parametric study on the behavior of tunnel face reinforced with horizontal pipes. A three-dimensional finite element model was adopted in this study to capture the three-dimensional nature of tunnel face behavior under various boundary conditions. A parametric study was peformed on a wide range of boundary conditions with emphasis on the effect of reinforcing layouts on the deformation behavior of tunnel face. The results of analysis such as tunnel face deformation behavior under various conditions were thoroughly analyzed, and a database for the behavior of tunnel face under different reinforcing conditions was established for future development of a semi-empirical design/analysis method for the tunnel face reinforcing technique. The results indicated that there exits an optimum reinforcing layout for a given tunnel condition, which must be selected with due consideration of tunnel geometry and ground condition.

• Geomechanics and Engineering
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• v.17 no.5
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• pp.439-444
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• 2019

It is generally known that high strength soil is indicative of well-graded particle size distribution. However, there are some special cases of firm ground despite poor grade distribution, especially a specific gap-graded soil. Based on these discoveries, this study investigated the development of an additive of gap-graded soils designed to increase soil strength. This theoretical concept was used to calculate the mixed ratio required for optimal soil strength of the ground sample. The gap-graded aggregate was added according to Plato's polyhedral theory and subsequently calculated ratio and soil strength characteristics were then compared to characteristics of the original soil sample through various test results. In addition, the underground stress transfer rate was measured according to the test conditions. The test results showed that the ground settlement and stress limit thickness were reduced with the incorporation of gap-graded soil. Further field tests would confirm the reproducibility and reliability of the technology by using gap-graded soil to reinforce soft ground of a new construction site. Gap-graded soil has the potential to reduce the construction cost and time of construction compared to other reinforcing methods.

• Journal of the Korean GEO-environmental Society
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• v.10 no.6
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• pp.35-48
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• 2009

An excessive ground displacement occurs with excavating tunnel in a fault zone because the fault has properties of soft ground in generally. It may have had a bad influence to adjacent structure. So, rapid reduction of ground strength by groundwater inflow should be prevented. It must be established for an impervious and reinforcing effect of ground to ensure a tunnel stability. The ground settlement and reinforcing effects were estimated by numerical analyses on tunnel through 570 m sector in Yangsan fault zone of Keongbu high-speed railway. Settlements evaluated by numerical analysis is similar to those calculated by using equation of Loganathan & Poulo. It was shown that reliable estimate of ground settlement by applying a prediction equation is possible. Applicability of adopted tunnel reinforcement method in fault zone was investigated by results of pilot construction and numerical analysis. Results from this study indicate that the adopted reinforcement method make tunnel displacements and member stresses restrain in design criteria.

• Journal of Korean Tunnelling and Underground Space Association
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• v.4 no.2
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• pp.91-100
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• 2002

This paper presents the results of laboratory investigation on the deformation behavior of tunnel face reinforced with longitudinal pipes. A series of reduced-scale model tests was carried out to investigate the effect of reinforcement layout on the tunnel face axial displacement as well as the surface settlement. Among other things, the results of the model tests indicate that the axial displacement of tunnel face as well as the ground surface settlement can significantly be reduced by pre-reinforcing the tunnel face with longitudinal pipes, suggesting that the pre-reinforcing technique may effectively be used as a positive ground control method in the urban environments. Also illustrated is that the reinforcing effect is significantly influenced by the reinforcement layout. The implications of the findings from this study are discussed in a great detail.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.03b
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• pp.247-254
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• 2000

In this study, the reinforcing effect of micropile for weathered rock is analysed by laboratory model tests. Especially, the effect of the number, the surface roughness, and length of micropile are focused. The results of tests are as follows: $\circled1$ The deformation modulus of reinforced ground is less than equivalent deformation modulus, and $\circled2$ Increasing effect of unconfined compressive strength is not large as times as increasing the number of micropile.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.10a
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• pp.499-509
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• 2005

We have many foundations which were constructed on the karstic areas where solution cavities and fractured zone may form under, or close to foundations. The fact that the ground under the pier foundations was reinforced with the three axial high pressure jet grouting is confirmed through out about two hundred design reports. It is necessary that evaluation of a simple application of high pressure jet grouting method on the karstic areas containing solution cavities. In this study, the improved situation and reinforcing methods of the ground under the pier foundations are proposed based on the evaluation of design reports for the express highway and No.38 national roads.

• Tunnel and Underground Space
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• v.20 no.1
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• pp.58-64
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• 2010

GLI model was verified to consider the interaction between a ground and a tunnel lining and to rationally reduce the ground load acting on the secondary lining(concrete lining) of a tunnel. In this study, the economy and the construction condition of tunnel concrete linings designed by a conventional frame model at Lot O of OO line were highly enhanced through a field design change using GLI model. For a few safe considerations, not only about 50% saving of reinforcing steel could reduce the material cost but also the wide space between bars could make it easy to pour concrete mix without voids. There was large saving effect of reinforcing steel for poor ground conditions because Terzaghi's load used in the conventional frame model produces too much high loads for those conditions.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.09a
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• pp.638-645
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• 2010

This study introduces a reinforcement work case using Twin-Jet Method. The area is located behind the abutment of the bridges built on soft clay along the $\bigcirc\bigcirc$ Express Highway. Its foundation was constructed by installing EPS blocks on the original ground to reduce the embankment load under the highway. However, the ground deformation has continuously occurred due to the settlement of the foundation soft cohesive soils. The amounts of subsidences at the surface turned out to be 20~30.0mm, After the pavement patch work on April 23, 2009, a drastic subsidence occurred together with 10mm swell, For this reason, Twin-Jet grout column construction was applied by passing through the EPS banking blocks without closing traffic flows on the express highway. The outcomes of core sample tests after reinforcing the ground turned out to be TCR 92.5%, RQD 64.6% and unconfined compressive strength 2.3~8.6Mpa. The test results showed that the condition of the ground foundation had improved using Twin-Jet grouting in most layers of ground including the cobble and gravel layer.