• Geomechanics and Engineering
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• v.6 no.3
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• pp.263-275
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• 2014

The development of transportation in large cities requires the construction of twin tunnels located at shallow depth. As far as twin tunnels excavated in parallel are concerned, most of the cases reported in literature focused on considering the effect of the ground condition, tunnel size, depth, surface loads, the relative position between two tunnels, and construction process on the structural lining forces. However, the effect of the segment joints was not taken into account. Numerical investigation performed in this study using the $FLAC^{3D}$ finite difference element program made it possible to include considerable influences of the segment joints and tunnel distance on the structural lining forces induced in twin tunnels. The structural lining forces induced in the first tunnel through various phases are considerably affected by the second tunnel construction process. Their values induced in a segmental lining are always lower than those obtained in a continuous lining. However, the influence of joint distribution in the second tunnel on the structural forces induced in the first tunnel is insignificant. The critical influence distance between two tunnels is about two tunnel diameters.

• Journal of the Korean Geophysical Society
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• v.6 no.4
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• pp.231-244
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• 2003

Lots of various utilities are buried under the surface of the earth. The effective handling of the underground utilities is becoming the big subject and project for the harmonious management and administration of the city. To detect the position and depth of buried underground utilities, GPR and Induced EM surveys are commonly used. However, they have limitations, such as shallow skin-depth and non-availability in the areas where subsurface materials are not homogeneous and are compose of clays and/or salts and gravels. The aim of this study is to find the efficient geophysical method which can overcome these limitations. For this purpose, various geophysical mehods were applied in the site of poor geotechnical environment.

• Journal of Navigation and Port Research
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• v.29 no.9
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• pp.783-788
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• 2005

This study provided the status and efficiency of the domestic wastewater sea outfalls based on the previous numerical and experimental studies for the analysis of the buoyant discharges from Rosette diffuser in shallow water. The VISJET model and the hybrid model proposed by Kim (2002) can be proper models for the domestic sea outfalls. The experimental results show that the merging height for MBR and MIR depends on the riser diameter and spacing between risers, and the bending characteristics of the buoyant discharges in still ambient water have significant impacts on the dilution. The current wastewater outfall systems in Korea are not effective for the environmental aspect due to the low discharge water depth. The strategies to reduce the contamination near the domestic wastewater outfalls were found to require the sufficient discharge water depth, proper diffuser location considering the tidal currents, enough riser diameter, and sufficient spacing between risers.

• Korean Journal of Soil Science and Fertilizer
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• v.28 no.3
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• pp.233-240
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• 1995

Fick's diffusion equation was transformed into algebraic subsidiary equation with its initial and boundary conditions through Laplace transformation, and the subsidiary equation was transformed back on the basis of Burington's table of inverse transformations so that it became the solution of Fick's equation. The initial and boundary condition was for upward diffusion of salts into flooding water of constant depth from uniform polder soil of infinite depth containing constant concentration of salt. The derived solution was tested through comparison for its conformability with other solutions of simpler initial and boundary conditions. The importance of shallow transplanting of rice seedlings and salt removing by growing rice was mentioned on the basis of very slow desalting rate by diffusion calculated from the derived solutions.

• Journal of the Korean Society for Nondestructive Testing
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• v.26 no.4
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• pp.231-238
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• 2006

Nondestructive examination for low pressure turbine disc in standard nuclear power plant using phased array technique was studied. For this purpose, disc mockups were made and notches were machined in the mockups. Detection and length sizing by different methods are compared. Depth of deep notches could be measured by using AATT(absolute arrival time technique) or RATT(relative arrival time technique) but shallow notches that must be detected in early stage couldn't be measured by these two methods. For this case, notch depth was estimated by using signal response angle range and preyed usefulness.

• Geomechanics and Engineering
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• v.13 no.5
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• pp.825-844
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• 2017

This study aimed to find out the pullout capacity of inclined strip anchor plate embedded in anisotropic and nonhomogeneous fully saturated cohesive soil in undrained condition. The ultimate pullout load has been found out by using numerical lower bound finite element analysis with linear programming. The undrained pullout capacity of anchor plate of width B is determined for different embedment ratios (H/B) varying from 3 to 7 and various inclination of anchor plates ranging from $0^{\circ}$ to $90^{\circ}$ with an interval of $15^{\circ}$. In case of anisotropic fully saturated clay the variation of cohesion with direction has been considered by varying the ratio of the cohesion along vertical direction ($c_v$) to the cohesion along horizontal direction ($c_h$). In case of nonhomogeneous clay the cohesion of the undrained clay has been considered to be increased with depth below ground surface keeping $c_v/c_h=1$. The results are presented in terms of pullout capacity factor ($F_{c0}=p_u/c_H$) where $p_u$ is the ultimate pullout stress along the anchor plate at failure and $c_H$ is the cohesion in horizontal direction at the level of the middle point of the anchor plate. It is observed that the pullout capacity factor increases with an increase in anisotropic cohesion ratio ($c_v/c_h$) whereas the pullout capacity factor decreases with an increase in undrained cohesion of the soil with depth.

• Geomechanics and Engineering
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• v.24 no.2
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• pp.143-156
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• 2021

Rail transit lines usually pass through many complicated topographies in mountain areas. The influence of inclined bedrock on the train-induced soil vibration response was investigated. Model tests were conducted to comparatively analyze the vibration attenuation under inclined bedrock and horizontal bedrock conditions. A three-dimension numerical model was built to make parameter analysis. The results show that under the horizontal bedrock condition, the peak velocity in different directions was almost the same, while it obviously changed under the inclined bedrock condition. Further, the peak velocity under inclined bedrock condition had a larger value. The peak velocity first increased and then decreased with depth, and the trend of the curve of vibration attenuation with depth presented as a quadratic parabola. The terrain conditions had a significant influence on the vibration responses, and the inclined soil surface mainly affected the shallow soil. The influence of the dip angle of bedrock on the peak velocity and vibration attenuation was related to the directions of the ground surface. As the soil thickness increased, the peak velocity decreased, and as it reached 173% of the embedded pile length, the influence of the inclined bedrock could be neglected.

• Geomechanics and Engineering
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• v.30 no.2
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• pp.123-138
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• 2022

Present study computes the ultimate bearing capacity of an embedded strip footing situated on the rock slope subjected to seismic loading. Influences of embedment depth of strip footing, horizontal seismic acceleration coefficient, rock slope angle, Geological Strength Index, normalized uniaxial compressive strength of rock mass, disturbance factor, and Hoek-Brown material constant are studied in detail. To perform the analysis, the lower bound finite element limit analysis method in combination with the semidefinite programming is utilized. From the results of the present study, it can be found that the magnitude of the bearing capacity factor reduces quite substantially with an increment in the seismic loading. In addition, with the increment in slope angle, further reduction in the value of the bearing capacity factor is observed. On the other hand, with an increment in the embedment depth, an increment in the value of the bearing capacity factor is found. Stress contours are presented to describe the combined failure mechanism of the footing-rock slope system in the presence of static as well as seismic loadings for the different embedment depths.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.1B
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• pp.111-114
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• 2008

Explicit solutions of the wave dispersion equation are developed using the recursive relation in terms of the relative water depth. We use the solutions of Eckart (1951), Hunt (1979), and the deep-water and shallow-water solutions for initial values of the solution. All the recursive solutions converge to the exact one except that with the initial value of deep-water solution. The solution with the initial value by Hunt converged much faster than the others. The recursive solutions may be obtained quickly and simply by a hand calculator. For the transformation of linear water waves in whole water depth, the use of the recursive solutions will yield more accurate analytical solutions than use of previously developed explicit solutions.

• Journal of the Earthquake Engineering Society of Korea
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• v.28 no.4
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• pp.205-213
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• 2024

In the seismic evaluation of underground utility tunnels, selecting an analytical method is critical to estimating reasonable seismic responses. In simplified pseudo-static analysis methods widely applied to typical seismic design and evaluation of underground tunnels in practice, it is essential to check whether the methods provide valid results for cut-and-cover tunnels buried in shallow to medium depth. The differences between the two simplified pseudo-static methods are discussed in this study, and the analysis results are compared to those obtained from FLAC models. In addition to the analysis methods, seismic site classification, overburden soil depth, and sectional configuration are considered variables to examine their effects on the seismic response of underground utility tunnels. Based on the analysis results, the characteristics derived from the concepts and details of each simplified model are discussed. Also, general observations are made for the application of simplified analysis methods.