• Journal of the Korea institute for structural maintenance and inspection
• /
• v.19 no.6
• /
• pp.72-79
• /
• 2015

An efficient and practical reliability evaluation method is proposed for the coastal structures in this paper. It is capable of evaluating reliability of real complicated coastal structures considering uncertainties in various sources of design parameters, such as wave and current loads, resistance-related design variables including Young's modulus and compressive strength of the reinforced concrete, soil parameters, and boundary conditions. It is developed by intelligently integrating the Latin Hypercube sampling (LHS), Monte Carlo simulation (MCS) and the finite element method (FEM). The LHS-based MCS is used to significantly reduce the computational effort by limiting the number of simulation cycles required for the reliability evaluation. The applicability and efficiency of the proposed method were verified using a caisson-type breakwater structure in the numerical example.

• Journal of the Korean GEO-environmental Society
• /
• v.15 no.12
• /
• pp.61-69
• /
• 2014

Carboxymethyl-${\beta}$-cyclodextrin (${\beta}$-CMCD), as a biodegradable surfactant with hydrophobic and hydrophilic properties, has potential advantages of being applicable to the simultaneous treatment of multiple contaminated soils. In this study, the desorption behaviors of r adionuclides such as cobalt (Co), strontium (Sr), and cesium (Cs) from the soil contaminated with them were experimentally investigated and the effectiveness of CMCD as a desorbent was evaluated. The desorption equilibrium of used radionuclides could be achieved within 1~3 hr and the desorption ratio from kaolin was higher than that from natural soil. The addition of CMCD of 2 g/L increased the desorption ratio by 5~20 % and the desorption ratio of used r adionuclides was shown in the order of Co > Cs > Sr. The experimental desorption data were fitted successfully by pseudo-second order kinetic model and the desorption rate of the r adionuclides was shown in the order of Cs > Co > Sr. Hysteresis between adsorption and desorption of the r adionuclides, as shown in the order of Sr > Co > Cs, increased as the desorption rate decreased. Consequently, it could be considered that the desorption rate was one of the significant factors of the hysteresis. The addition of CMCD as desorbent increased the amount of desorbed radionuclides and decreased the hysteresis. However, the CMCD could not completely desorb the radionuclides from soils even though the excess of CMCD was added.

• Explosives and Blasting
• /
• v.26 no.1
• /
• pp.23-37
• /
• 2008

The Dongdaemoon complex stadium is scheduled to remodelled into an international park, which will be named Design Plaza. The Dongdaemoon baseball field was constructed with Rahmen Structure which comprised beams, slabs and columns. In order to assure for viewing, the stadium was composed unusual structure that the height of the front column and the back column was designed differently. The bleachers was an upper arch form for viewing. The slab was not flat unliked the general infrastructure and tilted in stairway type for viewing. If we had applied the mechanical demolition method, we could have predicted several problems. Firstly, the stand could be unstable when the heavy equipment was to crush the reinforced concrete on the slab. Because the slab was not flat. Secondly, the construction expense and construction duration could be increase when the large equipment was to crush the reinforced concrete on the ground. Because the height of the stand was too high to crush on the ground so it needed to build a filling. Thus, we applied both the mechanical demolition method and explosives demolition method at the design stage. The result of explosives demolition was of complete success in terms of structural movement and controlled blasting noise and vibration. This case study provided a good example for a successful application of explosives demolition in urban areas.

• Journal of the Korean Geotechnical Society
• /
• v.25 no.4
• /
• pp.91-103
• /
• 2009

Slope failure depends upon the climatic features related to related rainfall, structural geology and geomorphological features as well as the variation of the mechanical behaviors of soil constituting a slope. In this paper, among many variables, effects of soil layer thickness on the slope failure process, and variations of matric suction and volumetric water content were observed. When the soil layer is relatively thick, the descending wetting front decreases matric suction and the observed matric suction reaches to "0" value. When the wetting front reaches to the impermeable boundary, the bottom surface of steel soil box, ascending wetting front was observed. This observation can be postulated to be the effects of various sizes of pores. When macro size pores exist, the capillary effects can be reduced and infilling of pore will be limited. The partially filled pores would be filled with water during the ascending of the wetting front, which bounces from the impermeable boundary. This assumption has been assured from the observation of variation of the volumetric water contents at different depth. When the soil layer is thick (thickness = 20 cm), for granular material, erosion is a cause triggering the slope failure. It has been found that the initiation of erosion occurs when the top soil is fully saturated. Meanwhile, when the soil layer is shallow (thickness = 10 cm), slope slides as en mass. The slope failure for this condition occurs when the wetting front reaches to the interface between the soil layer and steel soil box. As the wetting front approaches to the bottom of soil layer, reduction of shear resistance along the boundary and increase of the unit weight due to the infiltration occur and these produce complex effects on the slope failure processes.