• Journal of the Earthquake Engineering Society of Korea
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• v.11 no.1 s.53
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• pp.67-77
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• 2007

Site coefficients in IBC and KBC codes have some limits to predict the rational seismic responses of a structure, because they take into account only the effect of the soil amplification without the effects of the structure-soil interaction. In this study, upper and lower limits of the site coefficients are estimated through the pseudo 3-D elastic seismic response analyses of structures built on the linear or nonlinear soil layers taking Into account the effects of the structure-soil interaction. Soil characteristics of site classes of A, B and C were assumed to be linear, and those of site classes of D and E were done to be nonlinear and the Ramberg-Osgood model was used to evaluate shear modulus and damping ratio of a soil layer depending on the shear wave velocity of the soil layer, Seismic analyses were performed with 12 weak or moderate earthquake records scaled the peak acceleration to 0.1g or 0.2g and deconvoluted as earthquake records at the bedrock located at 30m deep under the outcrop. With the study results of the elastic seismic response analyses of structures, new standard response spectrum and upper and lower limits of the site coefficients of $F_{a}\;and\;F_{v}$ at the short period range and the period of 1 second are suggested including the effects of the structure-soil interaction, and new site coefficients for the KBC code are also suggested.

• Korean Journal of Environment and Ecology
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• v.27 no.6
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• pp.655-665
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• 2013

This study was carried out to investigate the community structure and biomass of benthic marine algae at the intertidal and subtidal zones of Eocheongdo on the western coast of Korea seasonally from July 2008 to April 2009. Total 101 species including 12 of green algae, 23 of brown algae and 66 of red algae were collected and identified. Among these species, 19 species were found throughout the year. The dominant species which contributed significantly to the total biomass were Corallina pilulifera, Gelidium elegans, Sargassum thunbergii, Sargassum fusiforme, Saccharina japonica, Sargassum honeri and Sargassum filicinum. Annual seaweed biomass in dry weight was $237.5gm^{-2}$ and maximum biomass was recorded seasonally in winter ($272.1gm^{-2}$), while minimum was recorded in summer ($204.5gm^{-2}$). The number of species and biomass of the subtidal zone were greater than those of the intertidal zone. The number of species and biomass in Eocheongdo seem to be higher than those of other islands in the western coast of Korea, due to the environmental conditions characterized by the increased transparency, and the well established rocky shore.

• The Journal of Engineering Geology
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• v.17 no.2 s.52
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• pp.289-297
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• 2007

Slope failure that is occurred by rainfall generates a lot of property damages and loss of lives. Slope stability management and reinforcement countermeasure can be attained through continuous monitoring about various slope types that adjoin in human's life for reducing slope failure from natural and artificial cut slope hazards. The study area is rock slope that is consisted of gneiss, and large scale joint set is ranging by fault activity. This rock mass is exposed during long period and has lithological weathering property of weathered rock or soft rock. In-situ investigation carried out after divide by natural slope and cut slope. As a result, the natural slope appeared to high possibility of planar failure and wedge failure in few joint points that main joint set is formed. On the other hand, slope failure conformation in cut slope was superior only wedge failure occurrence possibility in eight joint points. In result of numerical analysis using SLIDE 2D, the minimum safety factor was analyzed slope stability for cut slope relatively low than natural slope in this study.

• Tunnel and Underground Space
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• v.8 no.3
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• pp.209-225
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• 1998

Recently, Umbrella Arch Method(UAM), one of the auxiliary techniques for tunnelling, is used to reinforce the ground and improve stability of tunnel face. Because UAM combines the advantages of a modern forepoling system with the grouting injection method, this technique has been applied in subway, road and utility tunnel sites for the last few years in Korea. Also, several research results are reported on the examination of the roles of inserted pipes and grouted materials in UAM. But, because of its empirical design and construction methodology, more qualitative and systematic design sequences are needed. Therefore, above sequences using numerical analysis are proposed and, the effects of some design parameters were studied in this research. In order to acco,mplish these objects, first, the roles of pipe and grouting materials, steel-rib and the others in ground improving mechanism of UAM are clarified. Second, the effects of design parameters are investigated through parametric studies. Design parameters are as follows; 1) ground condition, 2) overburden, 3) geometrical formulation of pipes, 4) grouting region and 5) characteristics of pipes.

• Tunnel and Underground Space
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• v.16 no.2 s.61
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• pp.179-188
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• 2006

The vibration or/and noise generated by blast operations might cause not only structural damage to properties but mentally also to humans and animals. For that reason, maximum permitted vibration and noise levels are set by sensitivities of structures and they are used for the management of blast vibration. It is known that the fish lived in water are more sensitive to vibration than land animals, and thus the adverse impact of the blasting on fish farms should be very concerned. This study investigated the vibration and noise levels at a large eel farm located some 840 meters of the blasting site through the large real-scale experiments of blastings, prior to conducting the actual blasting. As a result, it was found that the noise met the requirement to be within maximum permitted level, while the ground vibration exceeded the permitted vibration. Accordingly, the impact of the excess vibration was investigated by an existing empirical method and verified by a new three dimensional numerical analysis. In this study, such an inspection process was briefly described, and a method was suggested for the examination of possible adverse effects from blasting on vibration-sensitive structures like the eel farm. The study also introduced a design method that controls the blast effects - ground vibration and noise.

• Tunnel and Underground Space
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• v.21 no.3
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• pp.151-163
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• 2011

The LCM test is one of the most powerful and reliable methods for designing the disc cutter and for predicting the TBM (Tunnel Boring Machine) performance. It has an advantage to predict the actual load on disc cutter from the laboratory test on the real-size large rock samples, however, it also has a disadvantage to transport and/or prepare the large rock samples and to need an extra cost for experiment. Moreover it is not easy to execute the test for jointed rock mass, and sometimes the design model estimated from the test can not be applied to the real design of disc cutter. In order to break this critical point, lots of numerical studies have been performed. PFC2D can simulate crack propagation and rock fragmentation effectively, because it is useful in particle flow analysis. Consequently, in this study, the PFC2D has been adopted for numerical analysis on cutting power of disc cutter according to the different angle of joint, the different direction of joint, and the different space of joint with jointed rock mass models. From the numerical analyses, it was concluded that the bigger cutting power of disc cutter was needed for reverse cutting direction to joint rather than for forward direction, and the cutting power of disc cutter was increased with decreasing the dip angle of joint and decreasing the space of joints in reverse cutting direction. The more precise numerical model for disc cutter can be developed from comparison between the numerical results and LCM test results, and the resonable guideline is expected for prediction of TBM performance and disc cutter.

• Tunnel and Underground Space
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• v.22 no.5
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• pp.346-353
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• 2012

Multi-specimen uniaxial compression test has been carried out in order to find the method to determine the five independent elastic constants from a single standard specimen of a transversely isotropic rock. Total 35 specimens of 7 different angles from a large block of rhyolite presenting the flow structure obviously are used in tests. This second report is to focus on the statistical evaluation of measured strains and analyzed elastic constants. And the determination of their true or near-true values is discussed. As the result of RSD analysis, it turns out that the reliability of measured strains is sufficiently obtained and Saint-Venant approximation is well applicable except 15 degree angled specimen in tests. RSD is decreasing on the increase of the angle of anisotropy. This tendency may be caused not only by the decreasing of the deviation of measured strains, but also by the better applicability of Saint-Venant approximation on the increase of angle. It can be concluded that the analyzed values are considered the near-true ones of five independent constants on the high reliability. But the variation of the apparent Young's modulus expected by these values is not proved to match the measured tendency. It is inferred that the factor to decrease the apparent Young's modulus and/or to increase the shear strain, is present in the test or in the nature of the anisotropy in consideration of this inconsistency.

• Tunnel and Underground Space
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• v.23 no.5
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• pp.383-391
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• 2013

A number of true triaxial tests on rock samples have been conducted since the late 1960 and their results strongly suggest that the intermediate principal stress has a considerable effect on rock strength. Based on these experimental evidence, various 3-D rock failure criteria accounting for the effect of the intermediate principal stress have been proposed. Most of the 3-D failure criteria, however, are focused on the phenomenological description of the rock strength from the true triaxial tests, so that the associated strength parameters have little physical meaning. In order to confirm the likelihood that the intermediate principal stress dependency of rock strength is related to the presence of weak planes and their distribution to the preferred orientation, true triaxial tests are simulated with the transversely isotropic rock model. The conventional Mohr-Coulomb criterion is extended to its anisotropic version by incorporating the concept of microstructure tensor. With the anisotropic Mohr-Coulomb criterion, the critical plane approach is applied to calculate the strength of the transversely isotropic rock model and the orientation of the fracture plane. This investigation hints that the spatial distribution of microstructural planes with respect to the principal stress triad is closely related to the intermediate principal stress dependency of rock strength.

• Tunnel and Underground Space
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• v.23 no.5
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• pp.353-361
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• 2013

Previous studies for analyzing optimal haulage routes of dump trucks in open pit mines mostly used raster data. However, the raster data has several problems in performing optimal route analyses: (1) the jagged appearance of haulage roads according the cell resolution often causes overestimation of the travel cost; (2) it difficult to trace the topological relationships among haulage roads. These problems can be eliminated by using vector network data, however a new method is required to reflect the performance characteristics of a dump truck according to terrain gradient changes. This study presents a new method to create vector network data with the consideration of terrain gradient for analyzing optimal haulage routes of dump trucks in open pit mines. It consists of four procedures: (a) creating digital elevation models, (b) digitizing haulage road networks, (c) calculating the terrain gradient of haulage roads, and (d) calculating the average speed and travel time of a dump truck along haulage roads. A simple case study at the Roto South pit in the Pasir open pit coal mine, Indonesia is also presented to provide proof that the proposed method is easily compatible to ArcGIS Network Analyst software and is effective in finding optimal haulage routes of dump trucks with considering terrain gradient in open pit mines.

• Tunnel and Underground Space
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• v.27 no.1
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• pp.26-38
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• 2017

In this study, bedding rock permeability was measured using Berea sandstones with three different beddings. The fracture permeability was also measured using tight sandstone with two different fracture regimes considering in-situ stress conditions. The Berea sandstone with vertical, horizontal and non-bedding was used to analyze evolution of permeability upon in-situ stress conditions. In order to describe applied effective stress around rock in underground, the triaxial pressure cell & hydrostatic pressure cell was designed and permeability experiments were performed with controlled axial and confining pressures. The measurement of permeability was conducted by increasing and decreasing effective stress. The permeability of non-bedding rock sample is the most sensitive to applied stress conditions and fracture permeability of tight sandstone increases with fracture treatment with proppant.