• Journal of Navigation and Port Research
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• v.33 no.3
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• pp.227-233
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• 2009

This experimental study has been carried out to investigate the reduction in side friction of open caisson using air-jet method. For this study, the large size caisson having air-pockets was used. This caisson was used as substructure of bridge. By using air-jet method, settlement time was decreased and even settlement was reached to the depth which conventional methods could not be. We found that the side resistance decreases to less then half the expected value. In addition to these merits, the air-jet method can result in self-weight settlement without applying additional load. Also the open caisson damage caused by blasting can be prevented with this method.

• Journal of the Korean Geosynthetics Society
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• v.22 no.1
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• pp.87-96
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• 2023

There are a lot of difference between the surface settlement and the differential settlement measured at the Busan New Port, where the dredged and reclaimed clay layer exists and below the clay is originally thickly distributed. To find the cause and solution of this, the actual conditions of each differential settlement used for the soft ground improvement, characteristics, installation method, measurement frequency, measurement data management, and data analysis of each type were considered. In the deep soft ground improvement work where large deformation occurs, the bending deformation of the screw-type differential settlement gauge is less than that of other types of measuring instruments, so there is less risk of loss, and the reliability of data is relatively high as the instruments are installed by drilling for each stratum. Since the greater the amount of high-precision settlement measurement data, the higher the settlement analysis precision. It is necessary to manage with higher criteria than the measurement frequency suggested in the standard specification. For the data management of the differential settlement gauge, it is desirable to create graphs of the settlement and embankment height of the relevant section over time, such as surface, differential, and settlement of pore water pressure gauge for each point. In the case of multi-layered ground with different compression characteristics, it is more appropriate to perform settlement analysis by calculating the consolidation characteristics of each stratum using a differential settlement data.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.974-981
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• 2005

Because general laboratory tests for sand compaction pile method including unit-cell test device have fixed outside diameter, as area replacement ratio increase, diameter of sand pile increase. These condition can bring about overestimation of stiffness of composite ground. In addition, existing large soil box which consist of bellows type loading plate can occur serious mistake in checking the amount of drained water because there are additional drainage along the inside wall in device. Overcoming these shortcoming, this paper developed modified large scale soil box consist of piston type load plate. In this study, using this device, series of modified large scale soil box tests were performed, and investigated the settlement and stress transportation characteristics with area replacement ratio in sand compaction pile method.

• 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.

• Journal of the Society of Disaster Information
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• v.3 no.1
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• pp.37-53
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• 2007

Various difficult problems occur due to insufficient bearing capacity or excessive settlements when constructing roads or large complexes. Accurate predictions on the final settlement and consolidation time can help in choosing the ground improvement method and thus enables to save time and expense of the whole project. Asaoka's method is probably the most frequently used for settlement prediction which are based on Terzaghi's one dimensional consolidation theory. Empirical formulae such as Hyperbolic method and Hoshino's method are also often used. However, it is known that the settlement predicted by these methods do not match with the actual settlements. Furthermore these methods cannot be used at design stage when there is no measured data. To find an elaborate method in predicting settlement in embankments using various test results and actual settlement data from domestic sites, Back-Propagation Neural Network(BPNN) and Recurrent Neural Network(RNN) were employed and the most suitable model structures were obtained. Predicted settlement values by the developed models were compared with the measured values as well as numerical analysis results. Analysis of the results showed that RNN yielded more compatible predictions with actual data than BPNN and predictions using cone penetration resistance were closer to actual data than predictions using SPT results. Also, it was found that the developed method were very competitive with the numerical analysis considering the number of input data, complexity and effort in modelling. It is believed that RNN using cone penetration test results can make a highly efficient tool in predicting settlements if enough field data can be obtained.

• Magazine of the Korean Society of Agricultural Engineers
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• v.42 no.5
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• pp.133-143
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• 2000

A large scale field test of prefabricated vertical drains was performed to anayze the effect of parameters of the very soft clay at a test site. compression index and the coefficient of horizontal consolidation obtained by back-analysis of settlement data were compared with those obtained by means of laboratory tests. Hyperbolic method, Asaoka meoth and curve fitting method were used to compute final settlement of coefficient of consolidation. The relationships of settlement measurement(Sm) versus design settlement(St) and the measurement consolidation ratio(Um) versus design consolidation (Ut) were shown as Sm=(1.0~1.1) St , Um=(1.13~1.17) Ut at 1.0m spacing of drain and Sm=(0.7~0.8)St, Um= (0.92~0.99) Ut at 1.5 m spacing of drain, respectively . The relationships of the field compression index(CcField) and virgin compression index(vcc lab) were shown as Ccfield =(1.0~1.2)vcc lab . But it was nearly within the same range when considering the error factor with the determination method of virgin compression index and the prediction back-analysis of the settlement data was larger than the coefficient of vertical consolidation, and the ratio of consolidation coefficient (Ch/Cv) was Ch =(2.4~2.9) Cv , Ch=(3.4~4.2) Cv at 1.0m and 1.5m spacing of drain, respectively.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.03a
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• pp.888-895
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• 2009

Compaction is a process of increasing soil density using physical energy. It is intended to improve the strength and stiffness of soil. In embankment, degree of compaction affects the construction time, money, also method of soil improvement. In large scale embankment project, difficulties of embankment should change due to uncertainty of settlement. So it is very important to predict the final settlement and factor of safety induced by embankment. In many construction site, there are primarily design of high embankment using in-situ soil. Therefore numerical analyses are necessary for valid evaluation of the settlement prediction. But due to the construction cost and schedule, there were lacking in properties of soil and also limited number of in-situ test were performed. So we proposed the method that can easily estimate the proper soil parameters and suggest the proper method of numerical analysis. From this, two-dimensional finite-difference numerical analysis was conducted to investigate the settlement and factor of safety induced by embankment with various case of compaction rate and embankment height.

• Korean Journal of Agricultural Science
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• v.37 no.3
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• pp.491-499
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• 2010

This study was carried out to investigate the consolidation characteristics of the remolded clay by the oedometer and the constant rate of strain(CRS) consolidation tests. As the rate of strain increases, the settlement rapidly decreased. As the ratio of the sand in the specimen increases, its effect on the rate of strain to the settlement was reduced. As the effective stress increased, the void ratio decreased, while the rate of strain increased, it did not show a clear variation. The reduction of the void ratio was shown to be less than the oedometer test. The coefficient of vertical consolidation with effective stress showed very large variation around preconsolidation stress, but the rate of strain did not provide significant effects. The rate of strain with effective stress gradually decreased at all tests and mixed ratio of sand. The rate of strain at the constant rate of strain tests showed smaller than in the oedometer test. The coefficient of consolidation at the constant rate of strain tests showed much more increase than in the oedometer test. The ratio of the vertical coefficient of consolidation by the odometer and the constant rate of strain tests showed a large difference according to various tests method and mixing ratio. Therefore, it is recommended that careful attention should be paid to designing the soft ground improvement.

• Journal of the Korean GEO-environmental Society
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• v.10 no.3
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• pp.63-71
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• 2009

The movement of in-situ walls has become very important as construction in large cities moves upward, instead of outward. Tall structures typically have deep excavations not on1y to provide extra space for parking, but also to reduce the potential settlement of the building. These large excavations require a robust bracing system to resist the lateral earth pressures as the depth increases. Methods to predict deflections of the retaining systems are of utmost importance because wall movements allow potentia1 settlement of adjacent structures. Case studies will be analyzed and measured waI1 def1ections will be compared with predictions from empirica1ly derived charts.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.362-371
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• 2006

The behaviour characteristics of Granular Compaction Pile(GCP) are mainly governed by the lateral confining pressure mobilized in the matrix soft soil to restrain the bulging failure of the granular compaction pile. The GCP method is most effective in soft soil with untrained shear strength ranging from $15\sim50\;kPa$. However, the efficiency of this method is falling down in the more compressible soil conditions, which does not provide sufficient lateral confinement. In the present study, the GCP method reinforced with uniformly graded permissible concrete is suggested for the extension of application to the soft ground. Also, large triaxial compression tests are conducted on composite- reinforced soil samples for verification of availability of the suggested method and the settlement estimation method of the reinforced GCP is proposed. Further, for the verification of a validity of the proposed method, predicted settlements are compared with results of numerical analyses. Tn addition, parametric studies are performed together with detailed analyses of relevant design parameters.