• Journal of the Korean Geosynthetics Society
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• v.12 no.4
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• pp.45-56
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• 2013

Recently, offshore wind farms are increasingly expected, because there are huge resource and large site in offshore. Jeju island has optimum condition for constructing a wind energy farm. Unlike the mainland, Jeju island has stratified structure distribution between rock layers sediments due to volcanic activation. In these case, it can be occur engineering problems in whole structures as well as the safety of foundation as the thickness and distribution of sediment under top rock layer can not support sufficiently the structure. In this paper, the settlement and stress distribution is predicted by numerical analysis when the mono-pile base are constructed on various soft layer between stratified structure. To determine the settlement of the pile foundation supported on stratified rock layer, the geological investigation at the 3 regiions and the results of laboratory experiments of the stratified rock layer is required.

• Earthquakes and Structures
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• v.12 no.3
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• pp.321-332
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• 2017

The reverse fault is a dangerous geological hazard faced by buried steel pipelines. Permanent ground deformation along the fault trace will induce large compressive strain leading to buckling failure of the pipe. A hybrid pipe-shell element based numerical model programed by INP code supported by ABAQUS solver was proposed in this study to explore the strain performance of buried X80 steel pipeline under reverse fault displacement. Accuracy of the numerical model was validated by previous full scale experimental results. Based on this model, parametric analysis was conducted to study the effects of four main kinds of parameters, e.g., pipe parameters, fault parameters, load parameter and soil property parameters, on the strain demand. Based on 2340 peak strain results of various combinations of design parameters, a semi-empirical model for strain demand prediction of X80 pipeline at reverse fault crossings was proposed. In general, reverse faults encountered by pipelines are involved in 3D oblique reverse faults, which can be considered as a combination of reverse fault and strike-slip fault. So a compressive strain demand estimation procedure for X80 pipeline crossing oblique-reverse faults was proposed by combining the presented semi-empirical model and the previous one for compression strike-slip fault (Liu 2016). Accuracy and efficiency of this proposed method was validated by fifteen design cases faced by the Second West to East Gas pipeline. The proposed method can be directly applied to the strain based design of X80 steel pipeline crossing oblique-reverse faults, with much higher efficiency than common numerical models.

• The Journal of Engineering Geology
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• v.7 no.3
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• pp.229-245
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• 1997

There are Common aspects between the underground oil storage cavern and the radioactive waste disposal facility. Both facilities use appropriately the intrinsic natural berrier characteristics of the rock mass and additionally the engineered barrier system for the long term safety. The geological structures and their hydrogeological characteristics in a faactured rock mass act a major role in the safety and performance of the underground oil storage facility through the design, construction and the operation stages. Because the fracture system distributed in a fractured rock block is complicated owing to their own geometrical and hydrogeological attributes, the hydrogeological perforrmrnce of the facility would depend mainly upon the understandings of their characteristics. This study reviews the uncertainties and key issues which have to be considered to analyse the groundwater flow system in a fractured rock mass and proposes the techniques applicable to characterize the hydrogeological parameter.

• Journal of Navigation and Port Research
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• v.28 no.7
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• pp.619-627
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• 2004

Introduction of wave model, considered the effect of shoaling, refraction, diffraction, partial reflection, bottom friction, breaking at the coastal waters of complex bathymetry, is a very important factor for most coastal engineering design and disaster prevention problems. As waves move from deeper waters to shallow coastal waters, the fundamental wave parameters will change and the wave energy is redistributed along wave crests due to the depth variation, the presence of islands, coastal protection structures, irregularities of the enclosing shore boundaries, and other geological features. Moreover, waves undergo severe change inside the surf zone where wave breaking occurs and in the regions where reflected waves from coastline and structural boundaries interact with the incident waves. Therefore, the application of mild-slope equation model in this field would help for understanding of wave transformation mechanism where many other models could not deal with up to now. The purpose of this study is to form a extended mild-slope equation wave model and make comparison and analysis on variation of harbor responses in the vicinities of Ulsan Harbor and Ulsan New Port, etc. due to construction of New Port in Ulsan Bay. We also considered the increase of water depth at the entrance channel by dredging work up to 15 meters depth in order to see the dredging effect. Among several model analyses, the nonlinear and breaking wave conditions are showed the most applicable results. This type of trial might be a milestone for port development in macro scale, where the induced impact analysis in the existing port due to the development could be easily neglected.

• Economic and Environmental Geology
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• v.42 no.6
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• pp.609-618
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• 2009

High permeable faults are important geological structures for fluid flow, energy, and solute transport. Therefore, high permeable faults play an important role in the formation of hydrothermal fluid (or hot spring), high heat flow, and hydrothermal ore deposits. We conducted 2-D coupled thermal and hydraulic modeling to examine thermohydraulic behavior in fault zones with various permeabilities and geometric conditions. The results indicate discharge temperature in fault zones increases with increasing fault permeability. In addition, discharge temperature in fault zones is linearly correlated with Peclet number ($R^2=0.98$). If Peclet number is greater than 1, discharge temperature in fault zones can be higher than $32^{\circ}C$. In this case, convection is dominant against conduction for the heat transfer in fault zones.

• The Journal of Engineering Geology
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• v.27 no.3
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• pp.345-351
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• 2017

Acid drainage in civil engineering structures such as tunnels may lead to the deposition of precipitates that clog drainage channels and pipework. In evaluating acid drainage, the Fe content of water and precipitates, indicated by reddish brown coloration of rock surfaces, rivers, and soils, may be an important factor. In this study, acid drainage was evaluated by analyzing the Fe content of reddish brown seepage water that occurred in part of a tunnel. Geological investigations around the tunnel revealed a hydrothermal alteration zone cutting the bedrock, and cropping out in the upper parts of the tunnel. Analysis of drillcore revealed many fracture zones and veins. Inductively coupled plasma spectrophotometric analyses of water, precipitates, and soil samples, collected in the seepage water zone and around the tunnel, were conducted to evaluate acid drainage. The Fe content of seepage water in the tunnel was 0.030-0.333 mg/kg, which is 2-22 times higher than in local groundwater. The Fe content of precipitates in the tunnel was 165,403-301,051 mg/kg, similar to the 206,167-422,964 mg/kg content of drillcore from the hydrothermal alteration zone located above the tunnel. It is concluded that the seepage water is derived from Fe-containing acid drainage flowing in perforated tunnel drainpipes along the fracture zones and veins around the hydrothermal alteration zone.

• Journal of the Korean Geotechnical Society
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• v.32 no.2
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• pp.5-17
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• 2016

Collapse of a tunnel can occur anytime, anywhere due to the special characteristics of tunnel structures and unexpected geological conditions during construction. Tunnel collapse will lead to economic losses and casualties. So various studies are continually being conducted to prevent economic losses, casualties and accidents. In this study, we analyzed data from 56 domestic construction tunnel collapse sites, and input factors to be applied to the artificial neural network were selected by the sensitivity analysis. And for the artificial neural network model design studies were carried out with the selected input factors and optimized ANN model to predict the type of tunnel collapse was determined. By using it, in 12 sites where tunnel collapse occurred applicability evaluation was conducted. Thus, the tunnel collapse type predictability was verified. These results will be able to be used as basic data for preventing and reinforcing collapse in the tunnel construction site.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2004.08a
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• pp.217-225
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• 2004

Introduction of wave model, considered the effect of shoaling, refraction, diffraction, partial reflection, bottom friction, breaking at the coastal waters of complex bathymetry, is a very important factor for most coastal engineering design and disaster prevention problems. As waves move from deeper waters to shallow coastal waters, the fundamental wave parameters will change and the wave energy is redistributed along wave crests due to the depth variation, the presence of islands, coastal protection structures, irregularities of the enclosing shore boundaries, and other geological features. Moreover, waves undergo severe change inside the surf zone where wave breaking occurs and in the regions where reflected waves from coastline and structural boundaries interact with the incident waves. Therefore, the application of mild-slope equation model in this field would help for understanding of wave transformation mechanism where many other models could not deal with up to now. The purpose of this study is to form a extended mild-slope equation wave model and make comparison and analysis on variation of harbor responses in the vicinities of Ulsan Harbor and Ulsan New Port, etc. due to construction of New Port in Ulsan Bay. This type of trial might be a milestone for port development in macro scale, where the induced impact analysis in the existing port due to the development could be easily neglected.

• Geotechnical Engineering
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• v.14 no.4
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• pp.91-102
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• 1998

Electrical resistivity method, one of the most widely used geophysical prospecting methods. has been usually applied to explorations for groundwater and underground resources. However, it has been extending its scope to civil & environmental engineering areas since it twas been developed so as to image underground structures effectively. A FEM algorithm for the dipole-dipole array was developed to correct topographic effects which have a serious influence on electrical methods. Applicability of the electrical resistivity imaging technique to civil & environmental engineering areas was verified through three case histories in this study First, thickness of soil layers was profiled to judge the possibility of developing borrow-pits tn an industrial complect site. Second, weak zones such as fractures and coal seams were detected to provide geological information for design and construction in a high mountain tunnel site. Third, horizontal/vertical distribution of the contaminated zone and depth of waste disposal were delineated in a completed industrial waste disposal site.

• Geomechanics and Engineering
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• v.12 no.6
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• pp.1003-1020
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• 2017

Estimation of groundwater inflow into underground opening is of critical importance for the design and construction of underground structures. Groundwater inflow into a pilot underground storage facility in China was estimated using analytical equations, numerical modeling and field measurement. The applicability of analytical and numerical methods was examined by comparing the estimated and measured results. Field geological investigation indicated that in local scale the high groundwater inflows are associated with the appearance of open joints, fractured zone or dykes induced by shear and/or tensile tectonic stresses. It was found that 8 groundwater inflow spots with high inflow rates account for about 82% of the total rate for the 9 caverns. On the prediction of the magnitude of groundwater inflow rate, it was found that could both (Finite Element Method) FEM and (Discrete Element Method) DEM perform better than analytical equations, due to the fact that in analytical equations simplified assumptions were adopted. However, on the prediction of the spatial distribution estimation of groundwater inflow, both analytical and numerical methods failed to predict at the present state. Nevertheless, numerical simulations would prevail over analytical methods to predict the distribution if more details in the simulations were taken into consideration.