• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.4C
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• pp.247-254
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• 2006

Online testing method is one of the numerical experiment methods using experimental information for a numerical analysis directly. The method has an advantage in that analysis can be conducted without using an idealized mechanical model, because mechanical properties are updated from element test for a numerical analysis in real time. The online testing method has mainly been used for the geotechnical seismic engineering, whose major target is sand. A testing method that may be applied to a consolidation problem has recently been developed and laboratory and field verifications have been tried. Although related research thus far has mainly used a method to update average reaction for a numerical analysis by positioning an element tests at the center of a consolidation layer, a weakness that accuracy of the analysis can be impaired as the thickness of the consolidation layer becomes more thicker has been pointed out regarding the method. To clarify the effectiveness and possible analysis scope of the online testing method in relation to the consolidation problem, we need to review the results by applying experiment conditions that may completely exclude such a factor. This research reviewed the results of the online consolidation test in terms of reproduction of the consolidation settlement and the dissipation of excess pore water pressure of a clay specimen by comparing the results of an online consolidation test and a separated-type consolidation test carried out under the same conditions. As a result, the online consolidation test reproduced the change of compressibility according effective stress of clay without a huge contradiction. In terms of the dissipation rate of excess pore water pressure, however, the online consolidation test was a little faster. In conclusion, experiment procedure needs to improve in a direction that hydraulic conductivity can be updated in real time so as to more precisely predict the dissipation of excess pore water pressure. Further research or improvement should be carried out with regard to the consolidation settlement after the end of the dissipation of excess pore water pressure.

• Journal of the Korean Geotechnical Society
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• v.30 no.2
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• pp.19-32
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• 2014

Carbonate sand of Sabkha layer in the middle east was made of deposition of shell fragments and it consisted of porous particles containing inner void. Generally, at yield stress the soil structure begins to break down, so the porewater pressure and the settlement are increased rapidly. In carbonate sand, unlike quartz sand if particle crushing happens, the inner voids are exposed and porewater pressure can be decreased under yield stress. Porewater pressure can be determined as the sum of excess porewater pressure due to increase of relative density, inner void expose of particle under particle crushing stress and rearrangement of crushed particle fragments. The porewater pressure can be negative value in case of greater amount of inner void expose, so if particle crushing is bigger, the porewater pressure value is smaller. The negative value zone of porewater pressure from triaxial test result means particle crushing effect is bigger than outer void decrease effect and the particle crushing effect dominant zone size was 1.50∼3.46% from triaxial test result of Sabkha layer.

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.4
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• pp.70-77
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• 2010

Microcement grouting and micro pile are frequently used for ground modification during tunnel construction. The influence of grouting pressure of microcement grouting and micro pile to the existing bridge which is directly over the constructing tunnel is investigated. Three dimensional seepage flow-structure interactive analysis considering firm water pressure with full stages of construction including the construction of upper bridge, microcement grouting, micro pile and tunnel is performed. The settlement and tilting of the pier of existing bridge violate the design code and the reaction of the bridge are highly increased after grouting. The stress of tunnel bracings such as rockbolt and shotcrete also exceed the limit of the code. The pressure of microcement grouting is confined by bedrock and transmit to the surrounded soil and the upper bridge. Microcement grouting needs mid-high pressure to penetrate through weak fault plane and the pressure greatly influence the safety of the upper structure. It is important to decide and care the grouting pressure to improve weak fault plane directly under the existing structures and the pressure of microcement grouting should be considered in underground analysis.

• Proceedings of the Korean Geotechical Society Conference
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• 1999.03a
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• pp.365-372
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• 1999

The plane deformation and spatial seepage(PDSS) analysis was developed to consider 3D flow of excess pore water as well as plane deformation of ground. Here is newly developed an equivalent model for PDSS analysis, which was the purpose to reduce number of finite elements and to take the effects of smear and well resistance into consideration. As the result of PDSS analysis with applying the new model, it is showed that the settlement-tin e relationship by PDSS agrees well with those of Plane strain(PS) and axisymmetric analyses, irrespective of existence of untreated layer. And the excess pore pressure distribution by PDSS is relatively agreed with that of axisymmetric analysis, not with that of PS.

• Journal of Industrial Technology
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• v.17
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• pp.103-110
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• 1997

This thesis is to investigate the one-dimensional consolidation behavior of soft marine clay with uniform surcharges by perfoming numerical and experimental works. Parametric experimental works of centrifuge model test were carried out changing test conditions of gravitational level in centrifuge, magnitude of surcharges and construction sequence of applying surcharges. Results of centrifuge model experiments were analyzed by using the numerical technique of explicit finite difference method based on the finite strain consolidation theory, being known to be appropriate to analyze the consolidational behavior of soft clay with a very high initial void ratio using the Lagrangian and the material coordinate systems. Test results were in relatively good agreements with analyzed results in terms of excess pore pressure dissipation and consolidation settlement with time and final void ratio distribution.

• Proceedings of the Korean Geotechical Society Conference
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• 1999.10a
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• pp.473-480
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• 1999

This paper presents the results of a parametric study on the behavior of mechanically stabilized earth retaining wall. It has been recognized that the currently available design guidelines, which is base on the limit equilibrium approach, cannot properly account the interaction effect between the components, construction sequence, and foundation settlement which may impose a significant influence on the wall behavior. A parametric study using finite element analysis was performed to investigate the behavior of MSE wall under different construction conditions and the applicability of the current design approach. In the parametric analysis, the effects of the construction sequence, the surcharge, and the foundation stiffness were studied and a detailed finite element modeling for various components of the system were employed. The results, such as wall displacement and earth pressure distributions, reinforcement forces, vertical stress distribution were then thoroughly analyzed to investigate the effect of construction details on the wall behavior.

• Journal of Korean Port Research
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• v.14 no.1
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• pp.115-124
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• 2000

This study is a suggest a measurement method of lateral displacement, which can be used to judge the stability of bridge abutment on soil undergoing lateral movement. The abutment of bridge on soft foundation makes lateral movement due to the settlement of back fill and lateral flow. To measure the displacement of such a abutment, there are a lot of indirect method for measurement such as survey of leveling or inclinometer gauge around the abutment. But all of them are not sufficient to confirm the ground behavior and measure the exact lateral behavior of structure. As making the structure and pile cooperatively by measuring the movement of lateral displacement, for measuring the abutment displacement precisely by using the inclinometer. In this work, we try to suggest efficient measuring method of abutment displacement and its application.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.10a
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• pp.461-468
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• 2005

The D-ROG(Digitalized Restoring of Grouting) Method is the restoring method for structures subjected to differential settlement and tilting by means of high grout injection pressure. This study investigate effect of grouting through in field test which applied D-ROG method in different condition(overload, ground condition).

• Journal of the Korean Society of Safety
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• v.13 no.2
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• pp.54-64
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• 1998

This study was initiated to examine the stress and deformation characteristics of the pipelines which were subjected to various environmental conditions in order to confirm their integrity. As the part of them, this paper presents the analysis results for the effect of ground subsidence combined with main loads on buried natural gas pipelines. The ground subsidence which can occur for buried gas pipeline has been classified to the three cases. Finite element method was used to analyze the effect of ground subsidences on pipeline of 26 inch(0.660 m) and 30 inch(0.762 m) diameter used as high pressure ($70 kg_f/cm^2(6.86 MPa)$) main pipelines of KOGAS. This paper shows the result of stress analysis for the pipelines subjected to those three case ground subsidence. Comparing these results with safety criterion of KOGAS(0.9 $\sigma_y$), maximum allowable settlement and loads have been calculated.

• Journal of The Korean Society of Agricultural Engineers
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• v.50 no.2
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• pp.45-52
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• 2008

Contaminant transport has been widely studied in rigid porous media, but there are some cases where a large volumetric stain occurs such as dewatering of dredged contaminated sediment, landfill liner, and in-situ capping. This paper presents a numerical investigation of contaminant transport coupled with large strain consolidation. Consolidation test was performed with contaminated sediments collected in Gary, Indiana, U.S. to obtain constitutive relationships, which are required for numerical simulations. Numerical results using CST2 show an excellent agreement with measured settlement and excess pore pressure. CST2 is then used to simulate contaminant transport during and after in-situ capping. Numerical simulations provide that transient advective flows caused by consolidation significantly increase the contaminant transport rate. In addition, the numerical simulations revealed that active capping with Reactive Core Mat (RCM) significantly decelerates consolidation-induced contaminant transport.