• Journal of Korean Tunnelling and Underground Space Association
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• v.25 no.6
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• pp.541-554
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• 2023

The utilization of underground spaces in relation to tunnels and energy/waste storage is on the rise. To ensure the stability of underground spaces, it is crucial to reinforce rock fractures and discontinuities. Discontinuities, such as joints, can weaken the strength of the rock and lead to groundwater inflow into underground spaces. In order to enhance the strength and stability of the area around these discontinuities, rock grouting techniques are employed. However, during rock grouting, it is impossible to visually confirm whether the grouting material is being smoothly injected as intended. Without proper injection, the expected increases in strength, durability, and degree of consolidation may not be achieved. Therefore, it is necessary to predict in advance whether the grouting material is being injected as designed. In this study, we aimed to assess the injection performance based on injection variables such as the water/cement mixture ratio, injection pressure, and injection flow using UDEC (Universal Distinct Element Code) numerical program. Additionally, numerical results were validated by the lab experiment. The results of this study are expected to help optimize variables such as injection material properties, injection time, and pump pressure in the grouting design in the field.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.2
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• pp.245-255
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• 1994

A two-dimensional Lagrangian finite-difference computer program is developed for the wave propagation analysis of impact phenomena. The numerical scheme is the standard method originally proposed by Von Neuman and Richtmyer, using artificial viscosity to smooth shock fronts. The material model used in the study is the standard hydrodynamic-elastic-plastic relations with Von-Mises yield criterion. A test configuration consisted of a target and a projectile were calculated to understand the response of a colliding event. However, the computer code is in plane strain, the calculations were intended for generating the qualitative features of the model behaviors. Nevertheless, the computational results were consistent with the experimental observations and provided a rational basis to interpret the modes of failures.

• Environmental Engineering Research
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• v.20 no.3
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• pp.212-222
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• 2015

Experiments were conducted on the immobilization of eight heavy metals (HMs) (Zn, Cu, Mn, Fe, Ni, Pb, Cd, and Cr) during 20-day rotary drum composting of water hyacinth. The Tessier sequential extraction procedure was used to investigate the fractionation of HMs. The eco-toxicity risk of HMs was assessed by risk assessment code (RAC). In the results, the bioavailability factor (BAF) for different HMs presented in the following order: Mn > Zn = Fe > Cu > Cr > Cd = Pb > Ni. The total concentration of Pb was higher than that of Zn, Cu, Mn, Cd and Cr; however, its BAF was the lowest among these HMs. These results confirmed that the eco-toxicity of HMs depends on bioavailable fractions rather than on the total concentration. The greatest reduction in bioavailability and eco-toxicity risk of HMs occurred in lime 1% and 2% as compared to control and lime 3%. The eco-toxicity risk of Fe, Ni, Pb, Cd and Cr was reduced from low risk to zero risk by rotary drum composting. These studies demonstrated the high efficiency of the rotary drum for degrading compost materials and for reducing the bioavailability and eco-toxicity risk of HMs during the composting process.

• Journal of computational fluids engineering
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• v.22 no.1
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• pp.95-102
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• 2017

Debris flow is a composition of solid objects of various sizes, suspension and water, which occurs frequently as the results of landslide following heavy rainfall. This often causes extensive damage in the form of socio-economic losses and casualties as witnessed during the incident around Mt. Umyeon, Seoul in 2011. There have been numerous investigation to mitigate the impacts from debris flow; however, the estimation as preparedness measure has not been successful due to nonlinear and multiphase characteristics of phenomena both in material and process inherent in the debris flow. This study presents a numerical approach to simulate the debris flow using open source code of computational fluid dynamics, OpenFOAM with non-Newtonian viscosity model for three phase material modeling. In order to validate the proposed numerical method, the quantitative evaluations were made by comparisons with experimental results and qualitative analysis for the dispersion characteristics was carried for the case of debris flow in the actual incident from Mt. Umyeon.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.12 no.2
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• pp.217-227
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• 1992

The first and second-order reliability method(FORM and SORM) is presented using one dimensional finite difference and two dimensional finite element transport models. FORM and SORM can be used without any restrictive assumptions about the properties of the media, and the sensitivity information obtained as part of these analyses is used to identify the parameters which have major influence on the estimate of probability. The reliability analysis of transport in a one-dimensional domain is used to test the robustness of the reliability code and to evaluate the accuracy of the reliability method. A continuous source 2-D example with a concentration threshold limit state function is used to evaluate the influence of the parameters in the location of interest on the reliability solution.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.12 no.4_1
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• pp.87-96
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• 1992

Moment Magnifier Method has been generally used in estimation of total column moment induced by geometric nonlinearity for reinforced concrete slender column design, however second order analysis such as P-${\Delta}$ method has been recommended by Code for better result. Member stiffness estimation is the most significant factor for accuracy of second order analysis. Equivalent Column stiffness based on theoretically obtained moment-curvature-thrust relationship has been proposed and the analytical results of the proposed method, MacGregor-Hage Method, Furlong's Method, and Moment Magnifier Method are compared with experimentally obtained data.

• Korean Journal of Computational Design and Engineering
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• v.20 no.4
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• pp.431-442
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• 2015

Currently, a BIM-based quantity takeoff (QTO) system is mainly focused on architectural projects. To perform this, diverse quantity takeoff methods such as an object-based automatic quantity takeoff, manual quantity and base functions of calculation have widely been utilizing. However, since BIM library for road projects includes structural elements associated with alignment, it is necessary to establish cost estimation system interlocked with historical cost using 3D library by each unit length. Accordingly, the aim of this study is to develop cost estimation model with using a historical cost approach so that it can be utilized in construction planning based on the BIM library for road projects. For this, based on the BIM library for road, the standardized quantity is estimated, and a process for calculating historical cost and a verification model with a 5D simulation was developed by mapping a WBS code with each BIM library object. This can be applied during the approximate cost estimation process in a project planning and an initial design phase for road projects. Besides, it is expected that these results will be utilized in constructing an optimal historical cost estimation process for project libraries.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.7 no.4
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• pp.1-12
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• 1987

The Advanced First Order Second Moment(AFOSM) method is commonly used to determine partial safety factors in the development of probability based LRFD code. However, design format using load and resistance factors based on this method may result in different reliability levels from specified ones. Reliability-Conditioned(RC) method recently proposed by Ayyub et al. gives partial safety factors which do not affect the target reliability level as specified. However, this method has some numerical difficulties and the procedure is not consistent. The proposed RC/AFOSM combined method has not only numerical consistency, but also results in almost constant partial safety factors with respect to various design conditions, and the resulting reliability levels are very close to specified ones.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.4A
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• pp.431-438
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• 2008

An updated Monte Carlo procedure for Typhoon simulation is presented to estimate the extreme wind speed at typhoon prone southern and western coasts in Korea. The reconstructed wind field model for typhoon in this study is compared with measured typhoon data for validation. The fitness of the proposed probability distribution models for typhoon parameters are tested by using data for the typhoon passed near the specific site. The simulated maximum wind speed associated with various return periods along southern and western coasts indicate that the extreme wind speed gradually increases inversely according to latitude of the coast, and that the basic wind speeds given in Korea Bridge Design Code are excessive compared with present results.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.6A
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• pp.881-891
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• 2008

The purpose of the present study is to investigate the influence of seasonal temperature variation on the thermal stresses in roller compacted concrete dam(RCD) structures. Using the finite element code, DIANA performs 2-D transient temperature and resultant stress analysis for RCD. Time variability of the mesh geometry is considered in order to simulate successive phases of the structure's construction. The main analysis variables are construction sequence, concrete temperature and ambient temperature. The results show principal tensile stress of hot-weathering concrete is higher than that of cold-weathering concrete. In some case the index of thermal cracking excesses 1.0, RCD also needs thermal management on placing temperature according to weather condition.