• Journal of the Korean Geotechnical Society
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• v.24 no.7
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• pp.43-50
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• 2008

Structures are frequently built on a dredged clay layer overlaid by a soft marine clay deposit in coastal areas of Korea. Large consolidation settlement usually occurs in the case and this may cause damages of super-structures. So, the evaluation of long-term consolidation settlement is very important in design and construction. Therefore, in this study, a long-term consolidation characteristics of marine dredged clays are investigated. Firstly, the relationship of $C_{\alpha}/C_c$ on marine dredged clays near Gwang-yang Port was evaluated. Secondly, long-term consolidation characteristics of the pseudo-preconsolidated ground were evaluated.

• Journal of the Korea institute for structural maintenance and inspection
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• v.11 no.4
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• pp.138-146
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• 2007

Geotechnical performance at the soft ground is strongly dependent on the properties of the soil beneath and adjacent to the structure of interest. These soil properties can be described using deterministic and/or probabilistic models. Deterministic models typically use a single discrete descriptor for the parameter of interest. Probabilistic models describe parameters by using discrete statistical descriptors or probability distribution density functions. The consolidation process depends on several uncertain parameters including the coefficients of consolidation and coefficients of permeability in vertical and horizontal directions. The implication of this uncertain parameter in the design of prefabricated vertical drains for soil improvement is discussed. A sensitivity analysis of the degree of consolidation and calculation of settlements to these uncertain parameters is presented for clayey deposits.

• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.2
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• pp.83-89
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• 2018

In this study, the settlement of concrete rectangular pyramid foundation on soft ground is investigated based on a finite element analysis. considering the grounding load and the grounding area of square pyramid foundation, we compensate the insufficient design bearing capacity and investigated the effect of settlement by load. Based on this study, it is found that the rectangular pyramid foundation shows the smallest settlement of three different type of foundations. As a result of this study, it was resulted that the square pyramid foundations were more effective than the crushed stone foundations by 18%. These results show that the ground pressures of the square pyramid bases are divided into horizontal and vertical stresses, so it is analyzed that the horizontal stress builds up the rigid ground on the foundation of the structure and distributes the load widely to increase the resistance to the overhead load.

• Journal of the Korean GEO-environmental Society
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• v.20 no.10
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• pp.29-38
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• 2019

In stability and settlement management of soft ground, the settlement prediction technology has been continuously developed and used to reduce construction cost and confirm the exact land use time. However, the preexistence prediction methods such as hyperbolic method, Asaoka method and Hoshino method are difficult to predict the settlement accurately at the beginning of consolidation because the accurate settlement prediction is possible only after many measurement periods have passed. It is judged as the reason for estimating the future settlement through the proportionality assumption of the slope which the preexistence prediction method computes from the settlement curve. In this study, ARIMA technique is introduced among time series analysis techniques and compared with preexistence prediction methods. ARIMA method was predictable without any distinction of ground conditions, and the results similar to the existing method are predicted early (final settlement).

• Journal of the Korean Geotechnical Society
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• v.21 no.3
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• pp.141-148
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• 2005

The settlement measured in the field shows a considerable difference from the predicted settlement due to various factors such as nonhomogeneous soft layers, sampling disturbance, erroneous selection of soil parameters and deficiency of consolidation theories among others. Therefore, analysis of actual settlement behavior based on the instrumentation and measurement data during consolidation period is a very useful procedure in evaluating the rates of consolidation settlement. This paper introduces a new practical method of analyzing consolidation settlement behavior, which is generalized and formulated from the existing analysis methods such as Hyperbolic method, Hoshino method and $\sqr{s}$ method. Through case studies, it is shown that the proposed method is a superior technique in reflecting the measured settlement behavior.

• Journal of the Korean GEO-environmental Society
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• v.5 no.2
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• pp.63-69
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• 2004

During and after the construction of embankment on soft ground, consolidation settlements and lateral displacements develop. But generally it's very difficult to predict the magnitude of lateral deformations and the correct distribution of lateral displacements with depth under the toe of embankment because the consolidation and the shear deformations of soft ground occur simultaneously. This study shows that later displacements of ground surface arise by embankment loading act on soft clay hight water contents in laboratory model testing. The results of model test are observed settlement of embankment, amount of maximum rising and displacement of ground surface with loading velocity. The formula were proposed to predict lateral movement by test series.

• Geotechnical Engineering
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• v.13 no.1
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• pp.137-146
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• 1997

In this study, a large consolidation test was carried out to estimate the consolidation behaviour of dredged clay ground improved by horizontal drain using plastic board drain with a vacuum pressure. The test results were analyzed by a numerical simulation using potential consolidation theory applied to a hollow cylinder. The rapid decreases in pore pressure and the drain speed in the plastic board indicate that the consolidation occurred quickly after the vacuum state was applied to the test soil. According to the numerical analysis obtained by applying the linear potential consolidation theory to a clay hollow cylinder with external radial drainage, the pore pressure is affected by the strain and the permeability of the soil rather than by the diffusion types. Therefore, measured surface settlement agreed with the numerical solution at the point where consolidation pressure increasing rate u: -0.5. Also the behaviour of the clay layer settlement in the place where the drain was installed was similar to that shown in Barron's consolidation theory. Finally, the design and construction procedure including the selection of the appropriate arrangement of horizontal drains were discussed based on the results of the laboratory tutsts. It is also shown that the potential consolidation theory make it possible to predict consolidation behaviour in the field using horizontal drains exactly.

• Geotechnical Engineering
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• v.14 no.2
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• pp.41-54
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• 1998

Predictions of consolidation settlement and time must be always erroneous because of heterogeneity of soil media. errors associated with the measurement of soil parameters, drawback of consolidation theories and so on. When filling is done on compressible soils, the observational procedure is a useful means in practice of evaluating the final consolidation settlement and time. However, the existing observational procedures including some disadvantages such as the difficulty of ending the linearity in the settlement curves, the unavoidable personal error, and so on. A new observational procedure($\sqrt{s}$ method) is suggested here for the consolidation analysis in field. As the results of applying the $\sqrt{s}$ method with other methods to two field data. the fecal settlements predicted by the s method as well as by the Asaoka'$\sqrt{s}$ method agreed well with the measured values. However, results obtained from the hyperbolic method(Tan, 1991) were always overestimated. and there happened many cases not to be predicted by the Hoshino's method. In the settlement curve from the $\sqrt{s}$method, the linearity between 60 and 90 eye of the average degree of consolidation is shown. and then the possibility of a personal error seems to be unusual. The final consolidation times(at $U_{95}$) predicted by the $\sqrt{s}$ method agreed well with the measured ones. but the ones by Asaoka and Tan(1996) methods were very much underestimated or overestimated. where $U_{95}$, is the average degree of consolidation of 95%. The big errors of these two methods seem to result from unconsidering the effect of stage construction.

• Korean Journal of Agricultural Science
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• v.29 no.2
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• pp.53-66
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• 2002

This study was performed to evaluation the consolidation behavior of agricultural reservoir in the very soft ground. The final settlement prediction methods by Terzaghi, Hyperbolic and Asaoka methods were used to compare with the degree of consolidation estimated by exess pore water pressure. The dissipated excess pore water pressure during embankment construction and peak excess pore water pressure on the completed embankment were suggested for the estimation of the degree of consolidation. It was concluded that the degree of consolidation estimated from dissipated excess pore water pressure was more reliable than that from the peak excess pore water pressure. The stability methods for agricultural reservoir was used to compare and analyze with various condition by limit equilibrium method.

• Geotechnical Engineering
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• v.12 no.5
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• pp.79-88
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• 1996

In this study, prediction of soil behavior under vacuum preloading with vertical drain is explored on the basis of numerical models and toe results were compared with field measurements. Reasonable prediction of the time rate of settlements and pore pressure dissipation under vacuum preloading is the maj or concern. The conventional method for vatsuum preloading is based on modeling vacuum preloading as surcharge loading for the consolidation analysis. However, this modeling may violate the real behavior of soils under vacuum loading since the total stress in the analysis varies due to the modeled surcharge loading whereas in'.situ total stress of soils under vacuum loading is constant. In this study a new method is suggested. Instead of modeling vacuum loading as surcharge loading, negative hydraulic head is applied at the surface drain boundary to simulate the vacuum preloading. Comparisons of predictions and field measurements of soil behavior under vatsuum preloading are presented and the usefulness of the new modeling technique is demonstrated.