• Geomechanics and Engineering
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• v.36 no.3
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• pp.259-276
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• 2024

The undrained shear strength is widely acknowledged as a fundamental mechanical property of soil and is considered a critical engineering parameter. In recent years, researchers have employed various methodologies to evaluate the shear strength of soil under undrained conditions. These methods encompass both numerical analyses and empirical techniques, such as the cone penetration test (CPT), to gain insights into the properties and behavior of soil. However, several of these methods rely on correlation assumptions, which can lead to inconsistent accuracy and precision. The study involved the development of innovative methods using extreme gradient boosting (XGB) to predict the pile set-up component "A" based on two distinct data sets. The first data set includes average modified cone point bearing capacity (q_t), average wall friction (f_s), and effective vertical stress (σ_vo), while the second data set comprises plasticity index (PI), soil undrained shear cohesion (S_u), and the over consolidation ratio (OCR). These data sets were utilized to develop XGBoost-based methods for predicting the pile set-up component "A". To optimize the internal hyperparameters of the XGBoost model, four optimization algorithms were employed: Particle Swarm Optimization (PSO), Social Spider Optimization (SSO), Arithmetic Optimization Algorithm (AOA), and Sine Cosine Optimization Algorithm (SCOA). The results from the first data set indicate that the XGBoost model optimized using the Arithmetic Optimization Algorithm (XGB - AOA) achieved the highest accuracy, with R2 values of 0.9962 for the training part and 0.9807 for the testing part. The performance of the developed models was further evaluated using the RMSE, MAE, and VAF indices. The results revealed that the XGBoost model optimized using XGBoost - AOA outperformed other models in terms of accuracy, with RMSE, MAE, and VAF values of 0.0078, 0.0015, and 99.6189 for the training part and 0.0141, 0.0112, and 98.0394 for the testing part, respectively. These findings suggest that XGBoost - AOA is the most accurate model for predicting the pile set-up component.

• Journal of the Korean GEO-environmental Society
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• v.12 no.12
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• pp.21-30
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• 2011

The recycled soil that is proceeded from demolition concrete structures was analyzed by the methods of the physical and mechanical tests of soil and TCLP test to use the soil in low landfilling for the construction of an industrial complex. The laboratory test for diffusion of alkali ion in soil mass was analyzed by the methods of XRF and ICP. The fish toxicity test was also conducted to find an environmental influence. The recycled soil through the laboratory test satisfied the engineering property for low landfilling and the criteria of soil contamination. However, the solution which producted by 1:1 ratio of recycled soil and water contained the high pH concentration by alkali ion. The calcium hydroxide solution by CSH cement paste was estimated as the main reason why pH concentration is increased more than 9.0. The high pH concentration in recycled soils causes a toxicity to the livability of fishes. A diffusion area of pH concentration in the ground was analyzed by the Visual Modflow Ver. 2009 program based on geotechnical investigation. The high pH concentration in the recycled soils can be remained as high value due to cement paste in the long term period. Therefore, in the early stage of landfilling work, the mixing with the weathered granite soil is necessary to control the pH concentration.

• Journal of Korean Tunnelling and Underground Space Association
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• v.24 no.5
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• pp.355-374
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• 2022

Soil conditioning improves the performance of EPB (earth pressure balance) shield TBMs (tunnel boring machines) by reducing shear strength, enhancing workability of the excavated soil, and supporting the tunnel face during EPB tunnelling. The mechanical and rheological behavior of the excavated muck mixed with additives should be properly evaluated to determine the optimal additive injection condition corresponding to each ground type. In this study, the laboratory pressurized vane test apparatus equipped with a vane-shaped rheometer was developed to reproduce the pressurized condition in the TBM chamber and quantitively evaluate rheological properties of the soil specimens. A series of the pressurized vane tests were performed for an artificial sand soil by changing foam injection ratio (FIR) and polymer injection ratio (PIR), which are the injection parameters of the foam and the polymer, respectively. In addition, the workability of the conditioned soil was evaluated through the slump test. The peak and yield stresses of the conditioned soil with respect to the injection parameters were evaluated through the rheogram, which was derived from the measured torque data in the pressurized vane test. As FIR increased or PIR decreased, the workability of the conditioned soil increased, and the maximum torque, peak stress, and yield stress decreased. The peak stress and yield stress of the specimen from the laboratory pressurized vane test correspond to the workability evaluated by the slump tests, which implies the applicability of the proposed test for evaluating the rheological properties of excavated soil.

• Advances in nano research
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• v.17 no.2
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• pp.181-195
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• 2024

This study introduces a novel functionally graded material model, termed the "Coated Functionally Graded Graphene-Reinforced Composite (FG GRC)" model, for investigating the free vibration response of plates, highlighting its potential to advance the understanding and application of material property variations in structural engineering. Two types of coated FG GRC plates are examined: Hardcore and Softcore, and five distribution patterns are proposed, namely FG-A, FG-B, FG-C, FG-D, and FG-E. A modified displacement field is proposed based on the higher-order shear deformation theory, effectively reducing the number of variables from five to four while accurately accounting for shear deformation effects. To solve the equations of motion, an analytical solution based on the Galerkin approach was developed for FG GRC plates resting on a viscoelastic Winkler/Pasternak foundation, applicable to various boundary conditions. A comprehensive parametric analysis elucidates the impact of multiple factors on the fundamental frequencies. These factors encompass the types and distribution patterns of the coated FG GRC plates, gradient material distribution, porosities, nonlocal length scale parameter, gradient material scale parameter, nanoplate geometry, and variations in the elastic foundation. Our theoretical research aims to overcome the inherent challenges in modeling structures, providing a robust alternative to experimental analyses of the mechanical behavior of complex structures.

• Journal of Energy Engineering
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• v.19 no.3
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• pp.143-150
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• 2010

Line source method of borehole system assumes the entire surrounding medium is uniform. However, thermal properties of grouting region are considerably different from those of surrounding soil. In this study we investigate the effect of grouting materials on the solution of line source method with the aid of numerical analysis. This numerical model generates the temperature of borehole fluid with which line source solution can be obtained. Then this solution can be compared with input condition of numerical model. The results of this comparison show that thermal conductivity and borehole thermal resistance of line source solution are approximately 86% and 91% of the input condition of numerical model. Chart method is developed in this study to find the numerical input conditions (thermal conductivity and borehole thermal resistance) from the line source solution. Thermal response test of test borehole is conducted, the results of which are approximately consistent with the Chart method. Thermal property changes of grouting materials on the line source solution are also examined.

• Journal of The Korean Society of Agricultural Engineers
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• v.54 no.4
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• pp.137-145
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• 2012

Sand is one of the essential materials used for social infrastructure construction such as embankment, landfill and backfill. It was known that mechanical properties and shear strength of sand are closely related to relative density. Therefore it is very important to determine accurate relative density. In this study, Portable Cone Penetration Tester (PCPT) was used to estimate the relative density and the internal friction angle of sand. PCPT cone-tip resistance ($q_c$) was measured changing the relative density of the two soil samples.Standard sand (JMJ) and Busan sand (BS). Also, a direct shear test was performed to investigate relationship between relative density and internal friction angle. The size and shape of soil particles were confirmed by using Scanning Electron Microscope (SEM). As a result, the log value of $q_c$ was linearly correlated with relative density and internal friction angle. In particular, the internal friction angle of BS sample was greater than that of JMJ, which was due to difference of the shape and mean size of particles. This result shows that it is important to determine the shape and size of particles as well as relative density to define mechanical property of sand. Through this study, it can be more effectively and conveniently to investigate relative density and shear strength of sand by using PCPT in situ.

• 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.

• Journal of Korean Society of Forest Science
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• v.89 no.2
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• pp.275-284
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• 2000

This study was carried out to analyze the mechanical properties of soil and the slope stability on the fill slope of forest road constructed in the regions which consist of igneous and metamorphic rock area. The results were summarized as follows. 1) Soil type by Unified Soil Classification System(USCS) was classified as SW in soil slope, GP in weathered rock slope, GP in soft rock slope for both types of parent rock, but gravelly soil slopes in igneous and metamorphic rock area were classified as SP and GW, respectively. 2) Dry unit weight was $1.34g/cm^2{\sim}1.59g/cm^2$, specific gravity 0.57~0.61, and void ratio 0.66~0.93 in the case of igneous rock area, a dry unit weight was $1.35g/cm^2{\sim}1.51g/cm^2$, specific gravity 2.67~2.77, and void ratio 0.78~1.01 in the case of metamorphic rock area. 3) The strength parameters such as internal friction angle(${\phi}$) and cohesion(c) were selected and tested for slope stability analysis. ${\phi}$ and c of soil in igneous rock area were within the range of $29.51^{\circ}{\sim}41.82^{\circ}$ and $0.03kg/cm^2{\sim}0.38kg/cm^2$, respectively, and $21.43^{\circ}{\sim}41.43^{\circ}$ and $0.05kg/cm^2{\sim}0.44kg/cm^2$ in metamorphic rock area, respectively. 4) Result of the slope stability analysis of forest road showed that, in the weathered rock slope of igneous rock and the weathered rock and soil slope of metamorphic rock area, the possibility of slope failure was high as safety factor was below 1.0.

• Journal of the Korean GEO-environmental Society
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• v.17 no.10
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• pp.55-62
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• 2016

The frequency slope over a year due to climate collapse is connected with huge casualties and property damage, but the situation rarely reduce the damage that gradually increases in size. In order to suppress this, engineers are improved better reinforcement and continued efforts to improve the shear force or withdrawal force. In this study, the GangWhaGu attached to the nail tip that improves the soil nail pullout resistance, and a method to increase the nail integral GangWhaGu maximize the contact area soil - by increasing the friction of the grout seems to increase the effect of slope stability. In order to validate the experiment to determine the effect of reinforcing the soil nail pullout tests of indoor and Behavior GangWhaGu nail and through field tests were conducted and applicability. Experimental results, the case of a pull-out test compared to the GangWhaGu nail through the tensile force of the nail were to increase by approximately 20%.

• Journal of the Korean Wood Science and Technology
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• v.43 no.6
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• pp.721-729
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• 2015

Wood properties depend on not only environmental factors such as soil, climate change, or forest stand characteristics, but also silviculture practices such as thinning, regeneration, or selection. This study report influences of the extent of thinning intensity from no thinning, moderate and heavy thinning to the wood property of Quercus acuta forest stands in Wan-do arboretum, Jeollanam-do Province. The results showed that there were close relationships between thinning intensity and anatomical, physical or mechanical properties of Quercus acuta wood. Especially, there are close relationships between thinning intensity and ring width or mechanical properties of wood. As a result, this study showed high correlations between Quercus acuta wood properties and thinning intensity of Quercus acuta forest stand. These findings are expected to be very useful as fundamental data for the implementation of silviculture practices of this specie to produce timber.