• Title, Summary, Keyword: Ground reinforcement

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Mining Subsidence and Ground Reinforcement (광산 지반침하와 대책)

  • 박남서;이치문;하은룡
    • Proceedings of the Korean Geotechical Society Conference
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    • pp.45-56
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    • 1999
  • There have been many coal mines abandoned since late 1980s in Korea. Due to the abandoned mines, there have been ground subsidences in some area where are under ground reinforcement works now. So, this study shows the general phenomena of mining subsidence and the procedure of ground reinforcement. In general the procedure for ground reinforcement is as below, 1) obtaining information from inquiries and observations, 2) satellite image analysis and surface geological mapping, 3) analysis of maps of coal mines, 4) geophysical survey and boring test and 5) selection of reinforcement method. The case of reinforcement design at Chul-am area, Kangwon Province is introduced in this article.

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An Analytical Study on the Determination of Reinforcement Length of Pile Slab Method (Pile Slab 공법의 보강길이 산정에 관한 해석적 연구)

  • Lee, Young-Keun;Park, Choon-Sik;Lee, Chae-Gun
    • Proceedings of the Korean Geotechical Society Conference
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    • pp.1232-1238
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    • 2008
  • From the result of analysis using finite element method for the Pile Slab reinforcement length through embankment of height, soft ground and the change of cohesion following results were acquired. 1. The higher embankment of height is, the deeper depth of soft ground is, the smaller cohesion is, Pile Slab reinforcement length increased almost straight. 2. The reinforcement length is controlled by the depth of soft ground, cohesion, embankment of height and the like. Among these, cohesion of soft ground is affected the most. 3. The reinforcement length of Pile Slab is determined using by calculated formula.

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Evaluation of Reinforcement Effects According to Reinforcement Type and Grouting Method (지반보강재의 형상과 그라우팅 방법에 따른 보강효과 평가)

  • Park, Jongseo;Kim, Taeyeon;Lee, Bongjik
    • Journal of the Korean GEO-environmental Society
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    • v.20 no.8
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    • pp.13-20
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    • 2019
  • In order to ground reinforcement, the chemical grouting, the anchor, the soil nailing system, the micropile, etc. can be mentioned by the methods widely used in domestic. The above ground reinforcement methods are developed by various methods depending on the type of reinforcement, installation method, presence of prestress, grouting method, etc. However, in common, the strength of reinforcement, the friction force of grout and reinforcement and the friction force of grout and ground are the main design variables. Therefore, the optimized ground reinforcement is a material with a high tensile strength of the reinforcement itself, the friction force between the reinforcement and the grout is high, and the application of an optimal grouting method is necessary to improve the friction force between the grout and the ground. In this study, a total of 20 model tests were conducted to analyze the reinforcement effects according to the shape of the reinforcement and the grouting method. As a result of the test, As a result of the experiment, it is judged that the reinforcing effect is superior to the perforated + wing type reinforcement and post grouting method.

A Case Study on Elephant Foot Method for Tunnelling in the Soft Ground (토사터널에서의 각부보강공법 적용성 연구)

  • Park, Chi-Myeon;Lee, Ho;Park, Jae-Hoon;Yoon, Chang-Ki;Hwang, Je-Don
    • Proceedings of the Korean Geotechical Society Conference
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    • pp.863-874
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    • 2009
  • The engineering characteristics and the reinforcement effect of the elephant foot method were discussed with parametric study. The elephant foot method is adopted to support the loads transferred from tunnel crown and improve bearing capacity of elephant foot in poor ground condition. The evaluation of reinforcement effect, which has the mechanical relationship between ground condition, footing size and reinforcement system, was carried out through the previous research and numerical analysis. In addition, the simple design chart was proposed to estimate the applicability of the elephant foot reinforcement method. It will be practical for the engineer to determine the optimum reinforcement method for safe tunnelling in soft ground condition.

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A study on the effects of ground reinforcement on the behaviour of pre-existing piles affected by adjacent tunnelling (터널근접시공에 의한 기 존재하는 인접말뚝의 거동에 지반보강이 미치는 영향에 대한 연구)

  • Jeon, Young-Jin;Kim, Sung-Hee;Kim, Jeong-Sub;Lee, Cheol-Ju
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.19 no.3
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    • pp.389-407
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    • 2017
  • In the current work, a series of three-dimensional finite element analysis was carried out to understand the behaviour of pile when the tunnel passes through the lower part of a single pile or group piles. At the current study, the numerical analysis analysed the results regarding the ground reinforcement condition between the tunnel and pile foundation. In the numerical modelling, several key issues, such as the pile settlements, the axial pile forces, the shear stresses and the total displacements near the tunnel have been thoroughly analysed. The pile head settlements of the single pile with the maximum level of reinforcement decreased by about 16% compared to the pile without ground reinforcement. Furthermore, the maximum axial force of the single pile with the maximum level of ground reinforcement experienced a 30% reduction compared to the pile without reinforcement. It has been found that the angle of ground reinforcement in the transverse direction affects the pile behaviour more so than the length of the ground reinforcement in the longitudinal direction. On the other hand, in the case of the pile group with the reinforced pile cap, the ground displacement near the pile tip appears to be similar to the corresponding ground displacement without reinforcement. However, it was found that the pile cap near the pile head greatly restrained the pile head movement and hence the axial pile force increased by about 2.5 times near the pile top compared to the piles in other analysis conditions. The behaviour of the single pile and group piles, depending on the amount of ground reinforcement, has been extensively examined and analysed by considering the key features in great details.

Analysis of the effect factors on behavior of the surface reinforced very soft ground (표층처리된 초연약지반 거동에 대한 영향인자 분석)

  • You, Seung-Kyong;Lee, Jong-Sun;Yang, Kee-Sok;Cho, Sam-Deok;Ham, Tae-Gew;Choi, Hang-Seok
    • Proceedings of the Korean Geotechical Society Conference
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    • pp.475-483
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    • 2008
  • It is necessary to develop a national design method for surface reinforcement of very soft ground because most current design works rely on crude empirical correlations. In this paper, the mechanical behavior of very soft ground that is surficially reinforced was investigated with the aid of a sents of numerical analysis. Several material properties of each dredged soft ground, reinforcement and backfill sand mat have been exercised the numerical analysis in order to compare the result of numerical analysis with those of the laboratory model test. Through the matching process between the numerical and experimental result, it is possible to find the appropriate material properties of the dredged soft ground, reinforcements and backfill sand mat. These verified material properties permit to show the effect of the stiffness of reinforcement and the thickness of sand mat on the overall deformation.

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Reinforcement Bulb Body Pull-out Resistance Force Behavior Characteristics according to Ground Conditions (지반조건에 따른 보강구근체 인발저항력 거동 특성)

  • An, JunYoung;Shim, JeongHoon;Jeong, JiSu;Lee, SeungHo
    • The Journal of Engineering Geology
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    • v.27 no.1
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    • pp.41-49
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    • 2017
  • In this study, we tried to confirm the influence range in the ground due to Bulbed, Reinforcement change and ground conditions change through numerical analysis. By checking the increase width of the reinforcement effect accompanying the increase of Bulbed, grasping the trend accompanying the change of the ground conditions and deciding soil nail Reinforcement and Bulbed, so that economical construction will be carried out It can be judged that it can be utilized as basic material. In this paper, we analyzed the Displacement due to positional load of reinforcement by utilizing MIDAS GTS NX which is a universal numerical analysis program. In addition, it is necessary to ensure the diameter star economy of Bulbed size and Reinforcement by comparing / analyzing whether the Bulbed relaxation region of Reinforcement represents arbitrary characteristics in the ground in Sandy soil, Weathered granite soil ground due to soil nail pullout load Numerical analysis was conducted to select criteria that can be done.

The effects of the face reinforcement at shallow tunnels in fractured rock masses (파쇄대 암반에서 얕은 심도의 터널 굴착시 막장보강효과에 관한 연구)

  • Nam, Kee-Chun;Heo, Young;You, Kwang-Ho
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.5 no.4
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    • pp.323-336
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    • 2003
  • Recently, the development of tunnel reinforcement method has been required relating to the shallow tunnelling in soft ground. In this study, the improvement method on tunnel stability is proposed by evaluating the efficiency of face reinforcement which enables to control extrusion of advance core, however, it is often neglected in urban tunnelling under the poor ground conditions. Systematic pre-confinement ahead of the face improves the tunnel stability, subsequently, displacement of the crown and surface settlement can be restrained by proper method. 3-dimensional numerical analysis including horizontal reinforcement modelling on a face is applied to estimate the behaviour of a tunnel in relation to the ground and reinforcement conditions. Consequently, extrusion at the face decreases significantly after using the horizontal reinforcement and the effect of reinforcement is much increased in case of applying the supplemental reinforcement ahead of the face together. Especially, confinement effect around the tunnel and the core is proved by means of the core reinforcement in poor ground conditions.

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A Case Study on the Ground Reinforcement Method and Effect of the Failed Tunnel (터널붕괴지반의 보강공법 및 효과에 대한 사례연구)

  • Cho, Hyun;Lim, Jae-Seung;Chung, Yoon-Young;Choi, Sang-Yeul
    • Proceedings of the Korean Geotechical Society Conference
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    • pp.293-300
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    • 1999
  • The maintenance for the stability of tunnel, especially on downtown area, careful check must be considered during construction stage and after. Moreover we have to achieve the stability of tunnel by ground improvement and reinforcement when ground condition is bad or tunnel failures under the various ground conditions. In this paper, it is presented the case of tunnel failure and the state of restoration by ground reinforcements at seoul subway $\bigcirc$-$\bigcirc$ construction site. For the purpose of ground reinforcement, first, curtain wall was established by chemical grouting. Secondly, cement milk grouting was carried by upper part of tunnel crown. Also Boreholes loading test and tunnel monitoring were carried by in failure site for the long term stability of tunnel.

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A Study on Determining the Design Parameter ($N_c$, $T_i$) of the Surface Reinforcement Method for Soft Ground (연약지반 표층처리공법 설계정수(지지력계수$N_c$, 인장력$T_i$) 산정방법에 관한 고찰)

  • Ham, Tae-Gew;Seo, Se-Gwan;Cho, Sam-Deok;Yang, Kee-Sok;You, Seung-Kyong
    • Proceedings of the Korean Geotechical Society Conference
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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.

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