• International Journal of Highway Engineering
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• v.11 no.3
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• pp.23-32
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• 2009

In this paper an experimental program was launched to determine the mechanical and durability properties of spall repair materials (RCC: 3 items, PCC: 2 items, PC: 3 items). Test items were mechanical property tests such as setting times, strengths, modulus of elasticity, plastic shrinkage, and durability tests such as dynamic modulus ratio, bond property with freeze-thaw, water absorption, chemical resistance, ultraviolet exposure. Modulus of the PC products exhibits ductile while the modulus is in the order of RCC > PCC > PC. At early ages the PC products experience higher plastic shrinkage than others, henceforth stable at 28 days. Other test results such as dynamic modulus ratio, absorption, and chemical resistance show that the PCs are superior to the PCCs and the RCCs. Except for PC-2, all patch materials had bond strength more than 1.3MPa after freeze-thaw cycles of 200~300 while the PCs and the PCCs seem to be better than the RCCs. With 500 hours of ultraviolet exposure, all patch materials showed to have no crack or deterioration at the surface.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.44 no.2
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• pp.203-214
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• 2024

Ports often suffer pavement damage due to soft ground and heavy equipment operations, leading to issues such as differential settlement and cracks. In this study, we developed port concrete blocks and applied them to a port in two configurations to figure out settlement characteristics. Falling weight deflectometer (FWD) tests on asphalt pavement and block pavements were conducted to figure out deflection and bearing capacity. The block pavement with the cement treated base showed improved bearing capacity with the port operation since lower settlements were detected than asphalt pavement. In the cement treated base, the relative deflection ratio to asphalt concrete pavement was less than 1, indicating enhanced bearing capacity. LiDAR measurements identified multiple settlements in the crushed-stone base due to surface loads after construction. Both relative deflection ratio and LiDAR measurements suggested that block pavement can be widely applied to various port sites with its applicability and bearing capacity of cement-treated base.

• Journal of the Korean Geosynthetics Society
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• v.17 no.4
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• pp.65-72
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• 2018

Seismically induced settlement exceeding dam freeboard may lead to a dam failure. The prediction of settlement is important also because it is also reported to be strongly related to longitudinal crack width and depth, which are critical indices used for safe evaluation of dams. The empirical correlation derived from numerical simulations is most often used. In this study, two-dimensional dynamic nonlinear analyses are performed using representative CFRD and ECRD fill dams. A total of 20 recorded motions are used to account for the influence on ground motion intensity and magnitude. The calculated crest settlements are correlated to four ground motion parameters, which are peak ground acceleration (PGA), peak ground velocity (PGV), Aria Intensity ($I_A$), and magnitude. It is demonstrated that using ground motion parameters in addition to PGA can significantly increase the prediction accuracy.

• Journal of the Korea Institute of Building Construction
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• v.19 no.2
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• pp.105-112
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• 2019

Fine aggregate made of ferronickel slag(FNS) is similar to natural fine aggregates and is used in concrete structures both domestically and abroad, but its applications and research areas are limited. In this research, in order to expand the availability of FNS and improve the performance of cement mortar products, the applicability of FNS on dry mortar for floor was examined. Experimental results show that FNS improves flow of cement mortar because it has low absorption rate, spherical shape, and glassy surface. Also, the high stiffness of the FNS aggregate itself is considered to contribute to the improvement of cement mortar quality such as crack reduction by improving the compressive strength and shrinkage reducing. In addition, when FNS fine aggregate is applied, it was possible to secure the impact sound insulation performance equal to or higher than that of mortar using natural fine aggregate.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.1
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• pp.130-137
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• 2019

Precast concrete (PC) structure is one of the type of the structures which is made in a facility prior to installing it to a construction field. The contact surfaces between two PC structures should be treated for obtaining enough binding force by inducing prestressing force. However, in the many cases, the contact surface causes the crack and leakage of water. These cracks and water leakage can cause the corrosion of the rebar, and the corrosion of the rebar can severely reduce the long-term durability. In this study, the SMA wire connector is suggested to solve the problem with the contact surfaces between two PC structures. The pull-out resistance of the suggested SMA wire connector is evaluated by conducting the tests to find the effect of the number of wires, shape of connector part, and shape memory effect. As a result of this study, the empirical formula is suggested to estimate the pull-out resistance related with the effects of the shape of the connector, shape memory effect, and the adhesive force. The validity between the estimated pull-out resistance and the measured value is confirmed.

• Journal of Korean Society of Disaster and Security
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• v.14 no.4
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• pp.47-60
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• 2021

Recently, as the occurrence frequency of sudden floods due to climate variability increased, the damage of aging chuteway slabs of spillway are on the rise. Accordingly, a wide array of field survey, hydraulic experiment and numerical simulation have been conducted to find the cause of damage on chuteway slabs. However, these studies generally reviewed the flow characteristics and distribution of pressure on chuteway slabs. Therefore the derivation of damage on chuteway slabs was relatively insufficient in the literature. In this study, the cavitation erosion and hydraulic jacking were assumed to be the causes of damage on chuteway slabs, and the phenomena were reproduced using 3D numerical models, FLOW-3D and COMSOL Multiphysics. In addition, the cavitation index was calculated and the von Mises stress by uplift pressure distribution was compared with tensile and bending strength of concrete to evaluate the possibility of cavitation erosion and hydraulic jacking. As a result of numerical simulation on cavitation erosion and hydraulic jacking under various flow conditions with complete opening gate, the cavitation index in the downstream of spillway was less than 0.3, and the von Mises stress on concrete was 4.6 to 5.0 MPa. When von Mises stress was compared with tensile and bending strength of concrete, the fatigue failure caused by continuous pressure fluctuation occurred on chuteway slabs. Therefore, the cavitation erosion and hydraulic jacking caused by high speed flow were one of the main causes of damage to the chuteway slabs in spillway. However, this study has limitations in that the various shape conditions of damage(cavity and crack) and flow conditions were not considered and Fluid-Structure Interaction (FSI) was not simulated. If these limitations are supplemented and reviewed, it is expected to derive more efficient utilization of the maintenance plan on spillway in the future.

• Journal of Conservation Science
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• v.28 no.3
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• pp.235-245
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• 2012

Nondestructive deterioration diagnosis has been carried out for the former ore dressing plant of the Yongwha mine in Yeongyang (Registered Cultural Property No. 255). Deterioration rates about organic contaminant and soil of the upper part (7 to 13 layer) indicate higher than the lower part (1 to 6 layer) of the ore dressing plants. By contrast, deterioration rates such as crack, break out and discoloration of the lower part indicate very higher than the upper part. It is estimated that the plants of the lower part that mechanical and chemical process had been done for flotation were damaged severely by physicochemical weathering with reaction of concrete and chemical solution. As results of ultrasonic velocity measurement, average p-wave velocity of plants were measured 2,462m/s (compressive strength $529kgf/cm^2$). As for the analytical results of surface contaminants and soil compositions using P-XRF, they were identical with major elements (Cu, Zn, Pb, Fe and As) of ore minerals from the Yongwha mine. Therefore, the ore dressing plant should be treated by phytoremediation with conservation because heavy metals could impinged upon plants and natural environment.

• Journal of the Korean Geotechnical Society
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• v.19 no.6
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• pp.273-283
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• 2003

Fissured rock and soft ground always suggest, problems in the construction of the underground space. The stress release of the weak underground material by opening the underground space with a soft ground, fissures and joints can lead to the failure of the opening. Grouting of the weak rock and the soft ground, which is a process of injecting some bonding agents into the soft ground, is one of the measures to reinforce the soft ground and to prohibit the failure of the underground construction due to the stress release. The proper installation of the grouting is essential to ensuring the safety of the tunneling operation, so that the evaluation of the grouting performance is very significant. The general procedure of evaluating the grouting is coring the grouted section and measuring the compression strength of the core. However, sometimes when the grouted section is at the crown of the tunnel and the grouting is installed at a wide section, the coring is not good enough. This study is oriented to propose a new and a non-destructive procedure of evaluating the grouting performance. The proposed method is based on the wave propagation of elastic waves, and evaluates the shear stiffness of the ground and investigates the anomalies such as voids and cracks. The SASW ( Spectral-Analysis-of-Surface-Waves) method is one of the candidate s to make the inspection of the pouting performance, and is adopted in this study. The practical grouting activity was monitored by SASW method, and the proposed method was applied to the inspection of the grouting performance to check the verification of the proposed method.

• Economic and Environmental Geology
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• v.40 no.5
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• pp.661-673
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• 2007

Rock materials of the three-storied stone pagoda in the Cheongryongsa temple in Korea are mainly composed of gneissose two-mica granite and fine-grained granite. This stone pagoda shows structural instability due to cracks and breaking-out of the stones. The surface properties of the stone is highly degraded by various inorganic pollutants and epilithic biospecies. Therefore, this study carried out comprehensive deterioration diagnosis by non-destructive methods, and some conservation treatments base on the diagnosis were carried out to reduce weathering progress. As the treatments, the biospecies and lichen that covering on the stone surfaces were removed by dry and wet cleaning, and degraded concrete applied to the pagoda for restoration in the past was removed and repaired with epoxy resin. Oxidized iron plates inserted between the rock properties were also substituted titanium stainless steels. After all processes are completed, we sprayed consolidant on the rock surface. Finally, the ground of the stone pagoda was rearranged using small rock aggregates, and the fence was established for control of artificial deterioration by visitors and environmental maintenance.

• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.4
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• pp.297-303
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• 2018

With the changing trend of the building construction to high rising and large scaling, the underground structure has been increased, and its usage also increased and variety. Hence, to protect the underground structure against underground water, various water proofing methods has been developed. Among the many water proofing methods, the combined water proofing method using both asphalt seal and sheet has been widely used to secure the sufficient performance and decrease the construction failure. However, during the summer period of extremely high temperature conditions, the asphalt sealing materials were separated and leaked into the structure. Therefore, the aim of the research is to provide the quality standard of asphalt sealing material based on the various temperature changes depending on seasons. According to the experimental results, the temperature of the sealing materials applied on the slab was increased up to $54^{\circ}C$ which was $3^{\circ}C$ higher than the structure temperature of $51^{\circ}C$. Based on the melting test for asphalt sealing materials applied on the outside wall of the structure, in the case of water-dispersing typed materials showed significant melting down due to its slow evaporation and low viscosity. Furthermore, from the accelerated test conducted indoor conditions, a solvent-type and water-dispersing typed materials showed significant melting down due to their low viscosity and melting point in ambient conditions. Based on these results, viscosity and melting point are found as the important factors on asphalt sealing materials' quality, and it is necessary to designate the quantitative level of the viscosity and melting point for quality control.