• Title/Summary/Keyword: 지반 침하

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Analysis of the subsidence ares with 3D-GIS and clustering (3차원 GIS와 클러스터링 기법을 이용한 지반침하지역에 대한 지반분석)

  • 고와라;최선영;윤왕중;강문경;김진회
    • Spatial Information Research
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    • v.11 no.3
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    • pp.203-212
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    • 2003
  • An integrated 3D GIS-based approach for understanding underground environment is proposed and applied to a land subsidence in densely populated region. Bedrock and geological discontinues were treated as main factors in this study. Because land subsidence in this study area was caused by cavity owing to dissolved limestone in percolating ground water. Ground was classified according to bedrock types using a clustering method and geological information, N value, and RQD value of boreholes were visualized and integrated by 3D-GIS. Therefore it was possible to recognize underground space easily and analyze the ground information effectively.

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A preliminary study for numerical and analytical evaluation of surface settlement due to EPB shield TBM excavation (토압식 쉴드 TBM 굴착에 따른 지반침하 거동 평가에 관한 해석적 기초연구)

  • An, Jun-Beom;Kang, Seok-Jun;Kim, Jung Joo;Kim, Kyoung Yul;Cho, Gye-Chun
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.23 no.3
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    • pp.183-198
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    • 2021
  • The EPB (Earth Pressure Balanced) shield TBM method restrains the ground deformation through continuous excavation and support. Still, the significant surface settlement occurs due to the ground conditions, tunnel dimensions, and construction conditions. Therefore, it is necessary to clarify the settlement behavior with its influence factors and evaluate the possible settlement during construction. In this study, the analytical model of surface settlement based on the influence factors and their mechanisms were proposed. Then, the parametric study for controllable factors during excavation was conducted by numerical method. Through the numerical analysis, the settlement behavior according to the construction conditions was quantitatively derived. Then, the qualitative trend according to the ground conditions was visualized by coupling the numerical results with the analytical model of settlement. Based on the results of this study, it is expected to contribute to the derivation of the settlement prediction algorithm for EPB shield TBM excavation.

Evaluation of Size Effects of Shallow Foundation Settlement Using Large Scale Plate Load Test (대형 평판재하시험을 이용한 얕은 기초의 침하에 대한 크기효과 평가)

  • Kim, Kyung-Suk;Lee, Sang-Rae;Park, Young-Ho;Kim, Sung-Hwan
    • Journal of the Korean Geotechnical Society
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    • v.28 no.7
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    • pp.67-75
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    • 2012
  • This paper addresses the size effect of shallow foundation settlement in very dense weathered granite soil commonly encountered in bridge foundation. Load-settlement curves measured from the plate load tests of 5 different plate sizes in 2 sites were analyzed. The test results showed that the ground beneath the plate was considered not to reach the failure state and the settlement continuously increased proportionately as load increased. The result implies that settlement would govern the stability or serviceability of foundation on very dense weathered soil. The size effect is expressed as a relationship of subgrade reaction modulus to the size of plate. Compared with the previous relationships, the size effect in this result was more prominent and indicated that settlement prediction using the previous method could possibly underestimate the settlement of foundation in dense weathered granite soil.

Characteristics of Bearing Capacity and Settlement According to the Difference of Loading Plate Sizes (재하판의 크기에 따른 지지력 및 침하특성)

  • 정형식;김도열
    • Journal of the Korean Geotechnical Society
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    • v.18 no.4
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    • pp.179-188
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    • 2002
  • The scale effect should be considered to determine the bearing capacity and settlement of footings from plate-load test, because of the size difference between a footing and a loading plate. To analyze characteristics of bearing capacity and settlement according to the difference of loading plate sizes, model tests were performed with four different sizes of square plate, which are B=10, 15, 20, and 25cm respectively, on five different kinds of subsoils. Test results showed that the ultimate bearing capacity of a footing on the sand did not increase proportional to the traditional formula and the bearing capacity on the clay also increased a little with increasing the size of loading plate. The settlement of test plate on the sand did not increase as the traditional formula of Terzaghi and Peck (1967), and the settlement on the clay also did not increase proportional to the traditional formula.

A Study on the Behavior of Surface Settlement due to the Excavation of Twin TBM Tunnels in the Clay Grounds (점토지반에서 TBM 병렬터널 굴진 시 지표침하거동에 대한 연구)

  • You, Kwangho;Jung, Suntae
    • Journal of the Korean GEO-environmental Society
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    • v.20 no.2
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    • pp.29-40
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    • 2019
  • Mechanized constructions have been frequently increased in soft ground below sea bed or river bed, for urban tunnel construction, and for underpinning the lower part of major structures in order to construct a safer tunnel considering various risk factors during the tunnel construction. However, it is difficult to estimate the subsidence behavior of the ground surface due to excavation and needs to be easily predicted. Thus, in this study, when a twin tunnel is constructed in the soft ground, it is proposed a simpler equation relating to the settlement behavior and a corrected formula applicable to soft ground and large diameter shield tunnels based on the previously proposed theory by Peck (1969). For this purpose, it was analyzed to long-term measurement values such as the amount of maximum settlement, the subsidence range by ground conditions, and interference volume loss due to the parallel construction, etc. As a result, a equation was suggested to predict the amount of maximum settlement in the soft sediment clay ground where is located at the upper part of the excavation site. It is turned out that the proposed equation is more suitable for measurement data in Korea than Peck (1969)'s.

Effect of Groundwater Flow on the Behavior of Circular Vertical Shaft (지하수 유동을 고려한 원형수직구 거동분석)

  • Park, Heejin;Park, Jongjeon;Jeong, Sang-Seom
    • Journal of the Korean Geotechnical Society
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    • v.38 no.6
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    • pp.29-39
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    • 2022
  • This study investigates the behavior of a circular vertical shaft wall in the absence and presence of a groundwater table. The effects of wall deflection, backfill settlement, and earth pressure distribution around the circular vertical shaft caused by sequential excavations were quantified. The vertical shaft was numerically simulated for different excavation depths of the bearing layer (weathered soil, weathered rock, soft rock) and transient and steady-state flows in the absence of a groundwater table. The backfill settlements and influential area were much larger under transient flow conditions than in steady-state flow. On the contrary, the horizontal wall deflection was much larger in steady state than in the transient state. Moreover, less settlement was induced as the excavation depth increased from weathered soil to weathered rock to the soft rock layer. Finally, the horizontal stresses under steady- and transient-state flow conditions were found to exceed Rankine's earth pressure. This effect was stronger in the deeper rock layers than in the shallow soil layers.

A Study on Behavior Characteristics of Soft Ground by DCM Arrangement Type (DCM 배치 형상에 따른 연약지반 거동 특성에 관한 연구)

  • You, Seung-Kyong;Lee, Jong-Young;Hong, Gigwon
    • Journal of the Korean Geosynthetics Society
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    • v.20 no.4
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    • pp.125-131
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    • 2021
  • This study described the relationship of settlement-lateral displacement and settlement-heaving according to the DCM type using the model test results, in order to evaluate the behavioral characteristics of the soft ground improved with DCM. As a result, it was found that the total settlement of the model ground was relatively small in the soft ground, to which the DCM was applied, and the settlement was less in the order of the grid type, wall type, and pile type under the same load conditions. This trend was also the same for the lateral displacement and heaving. In addition, the relationship between settlement and lateral displacement of soft ground was analyzed to be similar to that of previous study (Leroueil et al., 1990). Therefore, the DCM of grid type was evaluated to be superior to other types for lateral flow and heaving in the improvement effect of soft ground.

Critical face pressure and backfill pressure of shield TBM considering surface settlements of saturated clayey ground (쉴드 TBM 굴진에 따른 포화 점성토 지반의 침하거동을 고려한 한계 굴진면압과 한계 뒤채움압)

  • Kim, Kiseok;Oh, Ju-Young;Lee, Hyobum;Choi, Hangseok
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.20 no.2
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    • pp.433-452
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    • 2018
  • The shield tunneling method can minimize surface settlements by preventing the deformation of tunnel face and tunnel intrados due to tunnel excavation. For this purpose, it is very important to control the operating conditions of shield TBM. The face pressure and backfill pressure for tail void grouting should be the most important and immediate measure not only to restrain surface settlement, but also to influence the effective stress and pore water pressure around the circumstance of tunnel during excavation. The reaction of the ground to the application of face pressure and backfill pressure relies on the stiffness and permeability of ground. Especially, the reaction of saturated clayey ground formations, which shows the time-dependent deformation, is different from the permeable ground. Hence, in this paper it was investigated how the TBM operating conditions, ground stiffness, and permeability impact on the surface settlement of saturated clayey ground. For this purpose, a series of parametric studies were carried out by means of the stress-pore water pressure coupled FE analysis. The results show that the settlement of soft clayey ground is divided into the immediate settlement and consolidation settlement. Especially, the consolidation settlement depends on the ground stiffness and permeability. In addition, the existence of critical face pressure and backfill pressure was identified. The face pressure and backfill pressure above the critical value may cause an unexpected increase in the ground settlement.

A Case Study on the Cause Analysis of Subsidence in Limestone Mine Using LiDAR-Based Geometry Model (라이다 기반 정밀 형상 모델 활용 석회석 광산 지반침하 원인분석 사례연구)

  • Hwicheol Ko;Taewook Ha;Sang Won Jeong;Sunghyun Park;Seung-tae Kim
    • Tunnel and Underground Space
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    • v.33 no.3
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    • pp.126-140
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    • 2023
  • In this study, the cause of subsidence in limestone mine was analyzed using a LiDAR-based geometry model. Using UAV and ground-based LiDAR systems, a precise geometry model was constructed for the subsidence surface and mine tunnel, and the results of on-site geological survey and rock mass classification were utilized. Through the geometry model, distribution of thickness of crown pillar and faults around the subsidence area, calculation of the volume of the subsidence area and subsidence deposit, and analysis of the subsidence surface inclination were conducted. Through these analyzes, the causes of ground subsidence were identified.

A Study on the Long-term Settlement Characteristics of Thick Clay Deposits Using Field Monitoring (대심도 연약지반의 현장계측을 이용한 장기침하거동특성 분석에 관한 연구)

  • Kwon, Hyun-Wook;Im, Jong-Chul;Chang, Ji-Gun;Kang, Sang-Kyun
    • Journal of the Korean Geosynthetics Society
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    • v.17 no.4
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    • pp.21-28
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    • 2018
  • Despite a number of studies on consolidation behavior that have been carried out in the Nakdong River estuary in Busan, these are focused on the prediction of final settlement during ground improvement process, and there is almost no research on the long-term settlement occurring after that. For the practical study on the long-term settlement, the field monitored settlement data that measured over 10 years in the Busan new port facilities area were used, and the final settlement and predicted time-settlement line were constituted by hyperbolic function. As a result, the measured settlements depend on the thickness of clayey soils, and the pattern were similar to each other and good agreement with the predicted time-settlement line using hyperbolic method. Also, the settlement in the lower non-improved layer occupied 62-76% of total settlement. Information about above results would be quite helpful to understand the long-term settlement behaviors as well as the non-improved layer's settlement is more careful consideration needed at design phase.