• Title/Summary/Keyword: Consolidation Settlement

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Evaluation of Spatial Distribution of Secondary Compression of Songdo Marine Clay by Probabilistic Method (확률론적 방법을 이용한 인천송도지반 이차압축침하량의 공간적 분포 평가)

  • Kim, Dong-Hee;Bae, Kyung-Doo;Ko, Seong-Kwon;Lee, Woo-Jin
    • Journal of the Korean Geotechnical Society
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    • v.26 no.9
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    • pp.25-35
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    • 2010
  • Settlement at reclamation area caused by secondary compression should be considered using spatial evaluating method because the thickness of consolidation layer varies at every location. Probabilistic method can be implemented to evaluate uncertainty of spatial distribution of secondary compression. This study spatially evaluated mean and standard deviation of secondary compression in the overall analyzing region using spatial distribution of consolidation thickness estimated by ordinary kriging method and statistical values of soil properties. And then, the area where secondary compression exceeds a design criterion at the specific time was evaluated using probabilistic method. It was observed that the area exceeding the design criterion increased as the variability of $C_{\alpha}/(1+e_o)$ increased or the probabilistic design criterion 0: decreased. It is considered that the probabilistic method can be used for the geotechnical design of soft ground when a probabilistic design criterion is established in the specification.

A Case Study on the Application of Gravel Pile in Soft Ground (Gravel Pile의 현장적용을 위한 시험시공 사례연구)

  • 천병식;고용일;여유현;김백영;최현석
    • Proceedings of the Korean Geotechical Society Conference
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    • 2000.02a
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    • pp.32-41
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    • 2000
  • Sand drain as a vertical drainage is widely used in soft ground improvement Recently, sand, the principal source of sand drain, is running out. The laboratory model tests were carried out to utilize gravel as a substitute for sand. Though which the characteristics of gravel are compared to those of sand for engineering purpose. Two cylindrical containers for the model test were filled with marine clayey soil from the west coast of Korea with a column in the center, one with sand, the other with gravel. Vibrating wire type piezometers were installed at the distance of 1.0D, 1.5D and 2.0D from the center of the column. The characteristics of consolidation were studied with data obtained from the measuring instrument place on the surface of the container. The parameter study was performed on the marine clayey soil before and after the test in order to verify the effectiveness of the improvement. The clogging effect was checked at various depth in gravel column after the test. In-situ tests area was divided into two areas by material used. One is Sand Drain(SD) and Sand Compaction Pile(SCP) area, the other is Gravel Drain(GD) and Gravel Compaction Pile(GCP) area. Both areas were monitored to obtain the information on settlement, pore water pressure and bearing capacity by measuring instruments for stage loading caused by embankment. The results of measurements were analyzed. According to the test results, the settlement was found to be smaller in gravel drain than in sand drain. The increase in bearing capacity by gravel pile explains the result. The clogging effect was not found in gravel column. It is assumed that gravel is relatively acceptable as a drainage material. Gravel is considered to be a better material than sand for bearing capacity, and it is found that bearing capacity is larger when gravel is used as a gravel compaction pile than as a gravel drain.

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Behavior characteristics of Soft Ground Improved by Granular Pile (Granular Pile에 의해 개량된 연약지반의 거동특성)

  • Chun, Byung-Sik
    • Journal of the Korean GEO-environmental Society
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    • v.2 no.4
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    • pp.63-72
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    • 2001
  • As construction cases on soft ground are increasing, the necessity of ground improvement is also increasing. Granular pile is one of the methods for soft clay and for loose sandy soil. In our country, SCP(Sand Compaction Pile) method using sand material has been mainly used to improve soft ground, but Granular pile with crushed-stone was not used much. However, alternative material such that crushed-stone is needed to substitute for sand due to the environmental and economical problems. In this study, staged load test and consolidation test were performed in the laboratory to observe the behavior of soft ground improved by Granular pile. In order to evaluate the characteristics such as bearing capacity, drainage, and settlement, sand and crushed-stone were applied as each pile material. The test results show that crushed-stone has higher bearing capacity and less settlement than those of sand under similar pore water pressure condition. Therefore, crushed-stone is determined to be appropriate as substitute for sand.

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Development of Real Time Monitoring Program Using Geostatistics and GIS (GIS 및 지구통계학을 이용한 실시간 통합계측관리 프로그램 개발)

  • Han, Byung-Won;Park, Jae-Sung;Lee, Dae-Hyung;Lee, Gye-Choon;Kim, Sung-Wook
    • Proceedings of the Korean Geotechical Society Conference
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    • 2006.03a
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    • pp.1046-1053
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    • 2006
  • In the large scale recent reclaiming works performed within the wide spatial boundary, evaluation of long-term consolidation settlement and residual settlement of the whole construction area is sometimes made with the results of the limited ground investigation and measurement. Then the reliability of evaluation has limitations due to the spatial uncertainty. Additionally, in case of large scale deep excavation works such as urban subway construction, there are a lot of hazardous elements to threaten the safety of underground pipes or adjacent structures. Therefore it is necessary to introduce a damage prediction system of adjacent structures and others. For the more accurate analysis of monitoring information in the wide spatial boundary works and large scale urban deep excavations, it is necessary to perform statistical and spatial analysis considering the geographical spatial effect of ground and monitoring information in stead of using diagrammatization method based on a time-series data expression that is traditionally used. And also it is necessary that enormous ground information and measurement data, digital maps are accumulated in a database, and they are controlled in a integrating system. On the abovementioned point of view, we developed Geomonitor 2.0, an Internet based real time monitoring program with a new concept by adding GIS and geo-statistical analysis method to the existing real time integrated measurement system that is already developed and under useful use. The new program enables the spatial analysis and database of monitoring data and ground information, and helps the construction- related persons make a quick and accurate decision for the economical and safe construction.

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Improvement Effects of Soft Ground by Granular Pile (Granular Pile에 의한 연약지반의 개량효과)

  • 천병식;김백영
    • Journal of the Korean Geotechnical Society
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    • v.18 no.5
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    • pp.43-54
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    • 2002
  • As construction cases of structure are increasing in the soft ground, the necessity of ground improvement is also increasing. Granular pile is one of the improvement methods for soft ground and for loose sandy soil. In domestic, SCP(Sand Compaction Pile) method using sand material has been mainly used to improve soft ground, but Granular pile with crushed-stone was not used much. However, alternative material such as crushed-stone is needed to substitute for sand due to the environmental and economical problems. In this study, staged load test and consolidation test were performed in the laboratory to observe the behavior of soft ground improved by Granular pile. In order to evaluate the characteristics such as bearing capacity, drainage, md settlement, sand and crushed-stone were applied as each pile material. The test results show that crushed-stone has higher bearing capacity and less settlement than those of sand under similar fore water pressure condition. Therefore, crushed-stone is determined to be appropriate as the substitute for sand.

Responses of high-rise building resting on piled raft to adjacent tunnel at different depths relative to piles

  • Soomro, Mukhtiar Ali;Mangi, Naeem;Memon, Aftab Hameed;Mangnejo, Dildar Ali
    • Geomechanics and Engineering
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    • v.29 no.1
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    • pp.25-40
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    • 2022
  • In this study, 3D coupled-consolidation numerical parametric study was conducted to predict the deformation mechanism of a 20 storey building sitting on (4×4) piled raft (with length of piles, Lp=30 m) to adjacent 6 m diameter (D) tunnelling in stiff clay. The influences of different tunnel locations relative to piles (i.e., zt/Lp) were investigated in this parametric study. In first case, the tunnel was excavated near the pile shafts with depth of tunnel axis (zt) of 9 m (i.e., zt/Lp). In second and third cases, tunnels were driven at zt of 30 m and 42 m (i.e., zt/Lp = 1.0 and 1.4), respectively. An advanced hypoplastic clay model (which is capable of taking small-strain stiffness in account) was adopted to capture soil behaviour. The computed results revealed that tunnelling activity adjacent to a building resting on piled raft caused significant settlement, differential settlement, lateral deflection, angular distortion in the building. In addition, substantial bending moment, shear forces and changes in axial load distribution along pile length were induced. The findings from the parametric study revealed that the building and pile responses significantly influenced by tunnel location relative to pile.

Behaviour of the Excess Pore Pressure Induced by Sand Mat on the Soft Clay (점토지반 샌드매트의 간극수압 거동)

  • Kim, Hyeong-Joo;Lee, Min-Sun;Paek, Pil-Soon;Jeon, Hye-Sun
    • Journal of the Korean Geotechnical Society
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    • v.22 no.8
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    • pp.55-62
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    • 2006
  • The design of sand mat should be reviewed by the behaviour of excess pore pressure which is obtained by combining characteristics of soft ground with the permeability of sand mat. In this paper, in order to investigate the distribution of hydraulic gradient of sand mat, a banking model test was performed using dredged sand as materials of sand mat, and these results were compared by the numerical analysis results utilizing Terzaghi's consolidation equation. The results show that the pore pressure was influenced by the settlement increasing in the central area of sand mat as the height of embankment increases, and uprising speed of excess pore pressure due to residing water pressure is delayed compared with the results of numerical analysis. Finally, the construction of sand mat should be spreaded to reduce the increased hydraulic gradient at the central area of embankment.

Load Carrying Capacity and Failure Mechanism of Geogrid Reinforced Stone Columns : Reduced-Scale Model Tests (지오그리드 보강 Stone Column의 파괴메카니즘 및 지지력 특성 - 축소모형실험을 통한 고찰)

  • Lee, Dae-Young;Song, Ah-Ran;Yoo, Chung-Sik
    • Journal of the Korean Geotechnical Society
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    • v.22 no.10
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    • pp.121-129
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    • 2006
  • Stone column is one of the ground improvement systems which is being used for accelerating consolidation and increasing bearing capacity for settlement sensitive structures like load embankments, bridge abutments, oil storage tanks etc. The effects of this method are enhancement of ground bearing capacity, reduction of settlement, prevention of liquefaction and prevention of lateral ground movement. Recently, geosynthetic reinforced (encased) stone column approach has been developed to improve its load carrying capacity through increasing confinement effect. Although such a concept has successfully been applied in practice, fundamentals of the method have not been fully explored. This paper presents the results of an investigation on the bearing capacity and failure mechanism of geogrid-encased stone column by model tests. The results of the analyses indicated improved bearing capacity of the geogrid reinforced stone column method over the conventional strone column method with no encasing.

Improvement Effect and Electrical Characteristics of Soft Ground with Plastic Electrode Spacing (전극간 거리에 따른 연약지반의 지반개량 효과와 전기적 특성)

  • Byeon, Inseong;Kang, Hongsig;Sun, Seokyoun;Han, Jeonghoon;Ahn, Kwangkuk
    • Journal of the Korean GEO-environmental Society
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    • v.17 no.1
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    • pp.13-19
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    • 2016
  • Soft ground stabilization is needed to construct large civil facilities on the soft clay ground. Pre-loading method, which is accelerating consolidation method, is generally used to stabilize the soft ground. However, pre-loading method is required long construction period and quantities of fill material. Therefore, electro-osmosis method is used to replace pre-loading method for stabilizing the soft ground. Electro-osmosis method is disadvantageous in constructive and economic aspects because it is needed a metallic electrode. So, in order to solve the those disadvantages, plastic electrode was developed to replace metallic electrode. Plastic electrode, which is made by using nano-technology on existing Plastic Drain Board (PDB), was used to supply the electric power. In this study, therefore, the model test was conducted to confirm the effect of improvement and electrical characteristics of soft ground by spacing of plastic electrode. The result shows that the effect of improvement of soft ground was decreased up to 45% by increasing electrode spacing and electrical characteristics on the soft ground were influenced by consolidation settlement with electrode spacing.

An Analysis of the Effect of PBD Discharge Capacity to Leave Period (방치기간에 따른 PBD의 통수능 효과 분석)

  • Lee, Keeyong;Park, Minchul;Jeong, Sangguk;Lee, Song
    • Journal of the Korean GEO-environmental Society
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    • v.12 no.10
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    • pp.39-49
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    • 2011
  • Recently PBD method, one of acceleration of consolidation methods is used in the soft ground to shorten consolidation time for fast settlement during construction. It is economical and easy to work. Discharge capacity of PBD is sensitive in proportion to thickness of soft ground layer, and drainage of PBD declines due to disturbance effect in surrounding ground by mandrel used for vertical drainage setting and setting machines and type. Also, deviation of discharge capacity is large according to ground condition, construction condition and soil properties. In addition, when embankment loading is not conducted instantly after PBD setting due to rain or lack of embankment material supply, it causes leaving period problems. But cause and analysis of those problems for discharge capacity is lack. So, in this test, ground improvement and discharge capacity is investigated by implementing composite discharge capacity test for analysis of an effect factor of PBD discharge capacity with leaving period. After fixing the vertical drain on a cylindrical cylinder, put churned sample into the cylinder. Then leave 0day, 30day, 60day and 90day. And then, load following the loading step of 30, 70 and 120kPa using a pressure device. As a result, the longer leaving period, discharge capacity is reduced. It is caused by a decrease of discharge area caused by creep transformation moisture absorption of PBD filter after long leaving period.