• Journal of the Korean Geotechnical Society
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• v.27 no.9
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• pp.55-66
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• 2011

The compulsory replacement method for soft ground treatment is simple but excellent in economic feasibility. However, the accurate replacement depth is not easy to properly predicted since an theoretical algorithm has not presently been established so far. In this research a prediction equation is proposed in a new form based on the liquid limit and natural moisture content rather than on the bearing capacity of the soft soil layer. The equation is based on the monitoring as well as the confirmatory boring at the site. In addition, the equation has been derived from the data obtained from the analysis of the characteristics of silt/clay of Sihwa region. The final prediction equation has been drawn by applying the regression analysis method.

• Korean Journal of Materials Research
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• v.33 no.5
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• pp.205-213
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• 2023

This paper reports the results of an experimental examination using X-rays to test annealing materials for lapped bearing steel (STB2), to confirm the validity of the weighted averaging analysis method. The distribution behavior for the α_𝜓-sin²𝜓 diagram and the presence or absence of differences in the peak method, half-value breadth method, and centroid method were investigated. When lapping the annealed bearing steel (STB2) material, a residual stress state with a non-directional steep gradient appeared in the surface layer, and it was found that the weighted averaging analysis method was effective. If there is a steep stress gradient, the sin²𝜓 diagram is curved and the diffraction intensity distribution curve becomes asymmetric, resulting in a difference between the peak method, half-value breadth method, and centroid method. This phenomenon was evident when the stress gradient was more than 2~3 kg/mm²/㎛. In this case, if the position of the diffraction line is determined using the centroid method and the weighted averaging analysis method is applied, the stress value on the surface and the stress gradient under the surface can be obtained more accurately. When the stress gradient becomes a problem, since the curvature of the sin²𝜓 diagram appears clearly in the region of sin²𝜓 > 0.5, it is necessary to increase the inclination angle 𝜓 as much as possible. In the case of a lapping layer, a more accurate value can be obtained by considering 𝜎₃ in the weighted averaging analysis method. In an isotropic biaxial residual stress state, the presence or absence of 𝜎₃ can be determined as the presence or absence of strain for sin²𝜓≈0.4.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.1157-1166
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• 2008

Critical surcharge value of silt ground polluted with garbage leachate to the dyes $q_{cr}=3.73c_u$ and ultimate bearing capacity value $q_{ult}=8.60c_u$. Lateral flow pressure at polluted silt ground was about $P_{max}$/3 and depth of maximum lateral flow pressure was found at that of H/3 of soft layer thickness(H). Expression of polluted silt ground of fracture baseline at stability control charge by Matsuo Kawamura is $S_v=3.56\exp\{0.51(Y_m/S_v)\}$.

• Journal of the Korean Society for Heat Treatment
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• v.8 no.3
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• pp.205-212
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• 1995

Effect of Mn addition on rolling contact fatigue of C-base induction hardened bearing steels has been investigated to develop inexpensive surface-hardened bearing steels with improved resistance to rolling contact fatigue. Fatigue tests were conducted in elasto-hydrodynamic lubricating conditions at a shaft speed of 5,000rpm, under max. Hertzian stress of $492kg/mm^2$. It was found in the C-Mn steels that effective depth of induction hardened layer and amount of retained austenite were slightly increased in comparison with those of C-base steels. finer interlamellar spacing of pearlite in the C-Mn steels was also observed using TEM. Decomposition of retained austenite during rolling contact fatigue was smaller in quantity in the C-Mn steels than C-base steels. This might be associated with enhanced mechanical stability of retained austenite with addition of Mn. Statistical analysis of fatigue life for C-Mn steels using Weibull distribution indicated that improved resistance to rolling contact fatigue was mainly attributed to transformation induced plasticity and mechanical stability of retained austenite.

• Journal of the Korean Geotechnical Society
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• v.26 no.6
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• pp.29-38
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• 2010

Micro-piles have been used to increase the bearing capacity or to restrain settlement of existing shallow foundation. Recently, micro-piles are used to support the shallow foundation, to stabilize the slope and to resist the sliding of retaining wall. Using the micro-piles in geotechnical engineering, some investigators have studied the effective installing method by model test or field test. But most of previous studies are chiefly focused on the micro-piles in sand or clay layer. If a rock layer exists in soil, the installing length of micro-piles may be determined by the depth of rock layer. In this case, the stiffness of pile may be changed by the installing length of pile, and so the installing method has to be altered by the changed stiffness of pile. Model tests have been conducted to study the installation method of micro-pile in soil with rock layer. As a result, when the ratio of length of pile is below 50 ($L/d{\leq}50$), installing of micro-piles in vertical position is effective regardless of the depth of rock layer. If the depth of rock layer is deeper than soil failure zone and the ratio of the length of pile exceeds 50 (L/d>50), installing of the micro-piles in sloped position is effective.

• Journal of the Korean Geotechnical Society
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• v.27 no.4
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• pp.5-20
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• 2011

A numerical analysis has been conducted to propose the effective installation methods of Micro-pile in a sandy soil or a soil with rock layer. As a result, the bearing capacity of reinforced soil by rigid Micro-pile has influence on a connection state of the tip of pile and surface of rock layer. But that by flexible Micro-pile has more influence on a penetration length of pile than the connection state of the tip of pile and surface of rock layer.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.6
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• pp.1439-1444
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• 1994

Laboratory model test results for the ultimate bearing capacity and allowable bearing capacity at various settlement levels conducted on a strip foundation supported by geogrid-reinforced clay soil have been presented. For mobilization of the maximum possible load-carrying capacity, the optimum width and depth of the reinforcement layers, and the location of the first layer of reinforcement with respect to the bottom of the foundation have been determined.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.145-156
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• 2009

Large diameter bored pile was selected as the foundation type for Taipei 101. The pile construction method and specific construction procedures were determined based on the results of trial installation and pile load tests. The baseline for foundation design was established using the friction versus depth characteristics of each ground layer obtained from the pile load tests. As the ground profile and depth to the top of rock formation varied significantly on this site, the pile length, bearing capacity and settlement for single pile were analyzed using the information interpreted from adjacent boreholes. The post grouting at pile tip was mandatory for pile construction. Nevertheless, it was treated as a measure reducing the influence of construction uncertainties and providing extra safety for the foundation system.

• Proceedings of the Korean Geotechical Society Conference
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• 1992.10a
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• pp.137-144
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• 1992

This paper reports a case study of dynamic consolidation. The objective of the study is to evaluate the effectiveness of ground improvement at the site for Hyundai Petrochemical Compound constructed at Daesan-Myeon, Seosan-Gun in the western shores of Korea. The site ground was prepared by filling on the existing soft marine deposit which consists of a loose granular soil layer and a medium stiff clay layer. For the stabilization of site ground, the compaction was executed in three different procedures with same pounder weigh, drop height and imprint spacing. The post investigation showed that the object was successfully achieved indicating a significant increase of bearing capacity of the treated ground. In this study the effectiveness of dynamic consolidation is evluated for various factors the applied energy, temping sequences, the radial distance from the imprint location and the depth of bed rock.

• Korean Journal of Materials Research
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• v.8 no.12
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• pp.1176-1181
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• 1998

Characteristics of high frequency induction- hardened bearing steel have been investigated using 0.55wt.% C-1.68wt.% Mn specimens produced by vacuum induction melting (VIM). The K4 value in DIN 57602 of the specimens was assessed to be 6.41, high level of cleanliness. The specimens were high frequency induction-hardened to form heterogeneous submicron- lath martensite in the surface hardened layer with about 2.5mm in effective depth. Rolling contact fatigue tests were conducted in elasto-hydrodynamic lubricating conditions under a maximum Hertzian contact stress of$ 492kgmm^{-2}$ . It was found that microhardness in the subsurface, up to about $500\mu\textrm{m}$ in depth, below the raceway of rolling contact fatigued specimens was increased in comparison with that of induction-hardened layers. The depth of maximum microhardness- increased region was about $100\mu\textrm{m}$ from surface, showing white etching area. Crack initiation and propagation in the white etching area below the raceway of rolling contact fatigued specimens were observed.