• Journal of the Computational Structural Engineering Institute of Korea
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• v.32 no.6
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• pp.425-434
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• 2019

It is important to ensure the seismic safety of pile-bent bridges constructed in areas with thick soft ground consisting of various soil layers against seismic motion in these layers. In this study, several synthetic seismic waves that are compatible with the seismic design spectrum for rock sites were generated, and the ground acceleration history of each soil layer was obtained based on ground analyses. Using these acceleration histories, each soil layer was modeled using equivalent linear springs, and multi-support excitation analyses were performed using the input motion obtained at each soil layer. Due to the nonlinear behavior of the soft soil layers, the intensity of the input ground motion was not amplified, which resulted in the elastic behavior of the bridge. In addition, inputting the acceleration history obtained from a particular layer simultaneously into all the ground springs reduced the response. Therefore, the seismic performance of this type of bridge might be overestimated if multi-excitation analysis is not performed.

• Journal of the Korean Geotechnical Society
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• v.27 no.4
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• pp.67-76
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• 2011

Numerical analyses were performed to analyze the behavior of a suction pile under lateral loads with different soil layer conditions (uniform clay layer, uniform sand layer, and multi layers consisting of clay and sand layers) and different loading locations (top, middle, and bottom of the suction pile). The results of the analyses revealed that, regardless of the soil layer conditions, the lateral resistances at the loading location of the middle of the suction pile were the maximum. For the given loading locations, the lateral resistances of the suction pile for the uniform sand layer were relatively higher than those for the multi layer. By analyzing translations and rotations of the suction pile, it was identified that the amount of translation was highly dependent on both the soil layer condition and the lateral loading location while the rotated angle varied significantly with the lateral loading location, but not much with soil layer condition.

• Journal of Soil and Groundwater Environment
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• v.21 no.1
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• pp.1-5
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• 2016

Capillary barriers, consisting of relatively fine-over-coarse materials, have been suggested as an alternative to traditional compacted soil covers. So, We were analysed to capillary barrier effect according to five cases of multi-layer cover systems. Water balance simulation was conducted with unsaturated flow model HELP to assess unsaturated hydraulic parameters such as hydraulic conductivity, climate affecting the performance of capillary barriers. Simulation were conducted for 5 Cases in the Ulsan area. Result of simulation indicated that three cases was formed unsaturated condition and capillary barrier effect.

• Journal of the Korean Geotechnical Society
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• v.19 no.3
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• pp.5-13
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• 2003

The soil nailing is one of the useful support-system in urban excavation because of the presence of other structures in the vicinity Since the soil nailing system was introduced, model experiments and theoretical studies have been performed to investigate behavior of soil nailed wall. However, there are few data in the case of multi-layered soil strata just like Seoul Metropolitan area in Korea. The feed back analyses are carried out using the measured wall displacement data for soil nailing construction sites with multi-layered strata in order to analyze the distance and the coefficients of extension zone of ground behind soil nailed wall. As a result, the distance of extension zone increased with increasing of the final excavation depth and the ratio of the distance to the final excavation depth was shown to be about 94% of the final excavation depth. Also, the coefficients of extension zone increased with enlargement of soil layer thickness and converged into constant value of 1.05. On the other hand, the maximum vertical displacements by the feed back analysis and Caspe's method were shown to be approximately 80%, 150~280% of the maximum horizontal displacement respectively.

• Journal of Soil and Groundwater Environment
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• v.7 no.4
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• pp.10-16
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• 2002

The multi-aquifer system separated by semipervious leaky beds was analyzed. The finite difference scheme of the Crank-Nicolson method is applied to obtain the solution for this system. The solution of this scheme was compared with the analytical solution for two-layer aquifer systems with one-dimensional steady state. The results showed a good agreement between analytical and numerical solution for two-layer aquifer systems. So, the numerical scheme can be extended to multi-aquifer system. When the pumping is tried for single or multi aquifer, the computation of the groundwater heads was possible for each aquifer in the multi-aquifer with two-dimensional system. So, it might be helpful for the effective groundwater management.

• Journal of Korean Society of societal Security
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• v.1 no.2
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• pp.79-85
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• 2008

In this study, a new procedure (Unified Dynamic Analysis Method) to evaluate the dynamic responses a bridge under earthquakes is proposed, which is not only considering the bridge motions but also the soil layer motions nearby the bridge footing in order to include the soil-structure interactions. lt is found that the dynamic responses of the whole bridge systems can be properly evaluate from using the proposed UDAM. The properties of the soil layers where the bridge is located can be included into the seismic analysis, and the multi-seismic excitations can also be considered easily.

• Journal of Korea Soil Environment Society
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• v.2 no.3
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• pp.59-67
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• 1997

To investigate the effects of organic matter and soil depth on soil water flow in a multi-layered soil, the saturated hydraulic conductivities(Ksat) were measured from the single- and multi-layered soil columns, that the soils were mixed with the oven-dried cow manure compost(CMC) at 4 different ratios such as 0, 2, 4, and 6% on a weight basis. The measured hydraulic conductivities(Ksat) were compared with theoretical hydraulic conductivity (Keff calculated by Jury's equation of effective hydraulic conductivity. In the single layered soil column saturated hydraulic conductivities(Ksat) were significantly decreased with increasing the application rate of compost. In the multi-layered the soil columns Ksat was also decreased with increasing rate of compost and soil depth. Calculated Keff showed the similar results of Ksat as obtained from the measured Ksat, whereas steadily increased with increasing soil depth. Therefore, modification of Jury's equation should be required to adapt theoretical Keff for Held application.

• Geomechanics and Engineering
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• v.35 no.4
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• pp.385-393
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• 2023

To analyze the consolidation with horizontal sand drains, the plane strain consolidation model under multi-ramp loading is established, and its corresponding analytical solution is derived by using the separation of variables method. The proposed solution is verified by the field measurement data and finite element results. Then, the effects of the loading mode and stress distribution on consolidation and dissipation of pore pressure are investigated. At the same time, the influence of hydraulic conductivity and thickness of sand blankets on soil consolidation are also analyzed. The results show that the loading mode has a significant effect on both the soil consolidation rate and generation-dissipation process of pore water pressure. In contrast, the influence of stress distribution on pore pressure dissipation is obvious, while its influence on soil consolidation rate is negligible. To guarantee the fully drained condition of the sand blanket, the ratio of hydraulic conductivity of the sand blanket to that of clay layer k_d/k_v should range from 1.0×10⁴ to 1.0×10⁶ with soil width varying from 100 m to 1000 m. A larger soil width correspondingly needs a greater value of kd/kv to make sure that the pore water can flow through the sand blanket smoothly with little resistance. When the soil width is relatively small (e.g., less than 100 m), the effect of thickness of the sand blanket on soil consolidation is insignificant. And its influence appears obvious gradually with the increase of the soil width.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.11a
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• pp.665-672
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• 2000

The problems of discontinuous layer interface are very important in the algorithm and programming for the analysis of multi-layered consolidation using a numerical analysis, finite difference method(F.D,M.). Better results can be obtained by the process for discontinuous layer interface, since it can help consolidation analysis to model the actual ground Explicit method is simple for analysis algorithm and convenient for use except for applying the operator Crank-Nicolson method represents implicit method, which have different analysis method according to weighting factor. This method uses different algorithm according to dimension. And, this paper uses alternative direction implicit method. The purpose of this paper provides an efficient computer algorithm based on numerical analysis using finite difference method which account for multi-layered soils with confined aquifer to determine the degree of consolidation and excess pore pressures relative to time and positions more realistically.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.4C
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• pp.109-116
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• 2011

In this study, dynamic response of a vertical shaft subjected to seismic loads was evaluated by three-dimensional Finite Element (FE) approach. The emphasis was on quantifying the ground conditions, input motions and direction of motions. A series of parametric analyses were carried out. From the results of FE analysis, more than 1.7 times increase in shear force and bending moment is obtained when the stiff layer was thinker than the soft layer. And all of the maximum values were occurred near the interface between the soil layers. The dynamic behavior of vertical shaft was significantly influenced by the different frequencies of the input motion, and normalized acceleration of surrounding soil was 3 times larger than vertical shaft.