• Tunnel and Underground Space
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• v.5 no.2
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• pp.134-143
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• 1995

Effects of blasting vibrations on curing concrete have not been well studied. As a result, unreasonable and strong blasting vibration constraints have been placed on blasting when it occurs in the vicinity of curing concrete. To study the effects of blasting on curing concrete blocks of 33.3X27.7X16.2 cm were molded and placed on the quarry. Several sets of concrete blocks were subjected separately to peak vibrations of 0.25, 0.5. 1.0, 5.0, and 10cm/sec. The impulses of blasting vibrations were applied with thirty-minute intervals. Along with unvibrated concrete blocks, the vibrated concrete samples cored with 60.3 mm in diameter were measured for elastic moduli, sonic velocity and uniaxial compressive strength. Test results can be summarized as follows; 1. The blasting vibrations between 6 and 8 hours after pour generally lowered on the uniaxial compressive strength of the concrete. 2. A low blasting vibration of 0.25 cm/sec did not affect the uniaxial compressive strength. As the magnitude of the blasting vibration increases, compressive strength of concrete is decreased. 3. Physical properties of the P-wave velocity, Young's modulus, and Poisson's ratio showed a weakly decreasing trend in the concrete blocks vibrated between 6 and 8 hours after pour.

• Magazine of korean Tunnelling and Underground Space Association
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• v.1 no.1
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• pp.81-87
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• 1999

Effects of blasting vibrations on curing concrete have not been well studied. As a result, unrealistic and costly blasting vibration constraints have been placed on blasting when it occurs in the vicinity of curing concrete. To study the effects of blasting, concrete blocks of $30\times20\times20cm$ were molded and placed on the quarry Different sets of concrete blocks were subjected to peak vibrations of 0.25, 0.5, 1.0, 5.0, and 10cm/sec. The impulses of blasting vibrations were applied at thirty minutes intervals . Along with unvibrated concrete blocks, the vibrated concrete samples with 60.3mm in diameters were measured for elastic moduli, sonic velocity and uniaxial compressive strength. Test results can be summarized as follows : 1) The blasting vibrations between 6 and 8 hours after pour generally have exerted bad influences on the uniaxial compressive strength of the concrete 2) Under low vibration of 0.25cm/sec variations of the uniaxial compressive strength were not shown. As the magnitudes of blasting vibration increased, compressive strength of concrete decreased. But under the vibrations between 5 and 10cm/sec decreases in strength were almost same. 3) Physical properties of the p-wave velocity, Young's modulus, and Poisson's ratio appeared to decrease for the concrete blocks subjected to vibration for 6 to 8 hours.

• Ocean Systems Engineering
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• v.11 no.1
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• pp.17-42
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• 2021

Articulated loading platforms (ALPs) belongs to a class of offshore structures known as compliant. ALP motions have time periods falling in the wind excitation frequency range due to their compliant behaviour. This paper deals with the dynamic behavior of a double hinged ALP subjected to low-frequency wind forces with random waves. Nonlinear effects due to variable submergence, fluctuating buoyancy, variable added mass, and hydrodynamic forces are considered in the analysis. The random sea state is characterized by the Pierson-Moskowitz (P-M) spectrum. The wave forces on the submerged elements of the platform's shaft are calculated using Morison's Equation with Airy's linear wave theory ignoring diffraction effects. The fluctuating wind load has been estimated using Ochi and Shin wind velocity spectrum for offshore structures. The nonlinear dynamic equation of motion is solved in the time domain by the Wilson-θ method. The wind-structure interactions, along with the effect of various other parameters on the platform response, are investigated. The effect of offset of aerodynamic center (A.C.) with the center of gravity (C.G.) of platform superstructure has also been investigated. The outcome of the analyses indicates that low-frequency wind forces affect the response of ALP to a large extent, which otherwise is not enhanced in the presence of only waves. The mean wind modifies the mean position of the platform surge response to the positive side, causing an offset. Various power spectral densities (PSDs) under high and moderate sea states show that apart from the significant peak occurring at the two natural frequencies, other prominent peaks also appear at very low frequencies showing the influence of wind on the response.

• 한국지구물리탐사학회:학술대회논문집
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• 1999.08a
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• pp.48-64
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• 1999

For quantitative evaluation of geotechnical engineering properties such as rippability and diggability, clear interpretation on the subsurface velocity structures should be preceded by figuring out top soil, weathered and soft rock layers, shape of basement, fracture zones, geologic boundary and etc. from the seismic refraction data. It is very important to set up suitable field parameters, which are the configuration of profile and its length, spacings of geophones and sources and topographic conditions, for increasing field data quality Geophone spacing of 3 to 5m is recommended in the land slope area for house land development and 5 to 10m in the tunnel site. In refraction tomography technique, the number of source points should be more than a half of available channel number of instrument, which can make topographic effect ignorable. Compared with core logging data, it is shown that the velocity range of the soil is less than 700m/s, weathered rock 700${\~}$1,200m/s, soft rock 1,200${\~}$1,800m/s. And the upper limit of P-wave velocity for rippability is estimated 1,200 to 1,800m/s in land slope area of gneiss. In case of tunnel site, it is recommended in tunnel design and construction to consider that tunnel is in contact with soft rock layer where three lineaments intersecting each other are recognized from the results of the other survey.

• The Journal of Engineering Geology
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• v.11 no.2
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• pp.163-174
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• 2001

For quantitative evaluation of geotechnical engineering properties such as rippability and diggability, clear interpretation on the subsUJiace velocity structures should be preceded by figuring out top soil, weathered and soft rock layers, shape of basement, fracture zones, geologic boundary and etC. from the seismic refraction data. It is very important to set up suitable field parameters, which are the configuration of profile and its length, spacings of geophones and sources and topographic conditions, for increasing field data Quality. Geophone spacing of 3 to 5m is reconunended in the land slope area of house land development site. In refraction tomography technique, the number of source points should be more than a Cluarter of available channel number of instrument and the subsurface structure interpretation can be decreased the artifact of inversion by topographic effect. Compared with core logging data, it is shown that the velocity range of the soil is less than 700m/s, weathered rock 700~1,200m/s, soft rock 1,200~1,800m/s on the velocity tomogram section. And the upper limit of P-wave velocity for rippability is estimated 1,200 to 1,800m/s in land slope area of gneiss.

• Economic and Environmental Geology
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• v.16 no.1
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• pp.51-61
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• 1983

By using local earthquake data, the Korean crust model and travel-time tables were determined. The upper crustal earthquakes (Hongsung event and Ssanggyesa event) were considered as auxiliary information, and the lower crustal earthquakes (Uljin event and Pohang event) played an important role in determining model parameters. The possible existence of Low Velocity Layer (LVL) in the upper mantle was suggested by discrepancy in the arrival times of Sariwon earthquake which occurred below Moho discontinuity. Computer program for the determination of the model parameters was developed in order to screened out the optimum parameters by comparing the travel times of observed data with theoretical ones. We found that the discontinuities of Conrad, Moho, and upper and lower boundaries of LVL have their depth of 15, 32, 55 and 75 Km, respectively. The velocities of P-and S-wave in the layers between those discontinities were found to be (1) 5.98, 3.40 Km/sec (2) 6.38, 3.79 Km/sec (3) 7.95, 4.58 Km/sec (4) unknown (5) 8.73, 5.05 Km/sec, respectively from the top layer. Travel-time tables were also computed for the inter-local earthquakes which have their direct wave paths above the LVL.

• The Journal of Engineering Geology
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• v.27 no.3
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• pp.323-330
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• 2017

For the formation identification, surface geological survey, drill core analysis, core description and well log analysis are widely used. Among them well log analysis is a popular method with drill core analysis, since it measures continuously physical properties at in-situ. In this study we calculated Thomsen anisotropic parameters (${\varepsilon},\;{\delta},\;{\eta}$) after applying Backus averaging method to the P wave velocity, S wave velocity, and density logs. The well log data application of Blackfoot, Canada, shows the formation could be divided by 12 layers. This shows that Thomsen anisotropic parameters for identifying formation using anisotropic parameters is useful if there is no natural gamma log that is widely used for the formation identification.

• Journal of the Korean Geophysical Society
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• v.5 no.2
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• pp.143-151
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• 2002

Bulku temple in the city of Kyungju, Korea, built in 791 and reconstructed in the 20th century, is the home of seven national treasures including two three-story stone pagodas, Dabotap (height 10.4m, width 7.4m, weight 123.2ton) and Seokgatap (height 10.8m, width 4.4m, weight 82.3 ton). An earlier archaeological investigation shows that stone pagodas have experienced severe weathering process which will threaten their stability. At the base part of Dabotap, an offset of the stone alignment is also observed. For the purpose of the structural safety diagnosis of two pagodas, we introduce the nondestructive geophysical methods. Site characteristics around the pagodas are determined by the measurement of multiple properties such as seismic velocity, resistivity, image of GPR(ground-penetrating radar). Near the pagodas, the occurrence of high resistivity (up to 2200 Ωm) is obvious whereas their outskirts have as low as 200 Ωm. For the velocity of the P wave, the site of Dabotap has the range of 500~800 m/s which is higher than counterpart of Seokgatap with the velocity of 300~500m/s, indicating the solider stability of Dabotap site. Consequently, in addition to GPR images, the foundation boundaries beneath each stone pagodas are revealed. The Dabotap site is in the form of an octagon having 6-m-long side with the depth of ~4m, whereas the Seokgatap site the 9m × 10m rectangle with the depth of 3m. These subsurface structures appear to reflect the original foundations constructed against the stone load of ~8 ton/㎡. At the subsurface beneath the northeast of each pagoda, low seismic velocity as well as low resistivity is prominent. It is interpreted to represent the weak underground condition.

• Geophysics and Geophysical Exploration
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• v.9 no.1
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• pp.19-29
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• 2006

The first Japanese pilot-scale $CO_2$ sequestration project has been undertaken in an onshore saline aquifer, near Nagaoka in Niigata prefecture, and time-lapse well logs were carried out in observation wells to detect the arrival of injected $CO_2$ and to evaluate $CO_2$ saturation in the reservoir. $CO_2$ was injected into a thin permeable zone at the depth of 1110m at a rate of 20-40 tonnes per day. The total amount of injected $CO_2$ was 10400 tonnes, during the injection period from July 2003 to January 2005. The pilot-scale demonstration allowed an improved understanding of the $CO_2$ movement in a porous sandstone reservoir, by conducting time-lapse geophysical well logs at three observation wells. Comparison between neutron well logging before and after the insertion of fibreglass casing in observation well OB-2 showed good agreement within the target formation, and the higher concentration of shale volume in the reservoir results in a bigger difference between the two well logging results. $CO_2$ breakthrough was identified by induction, sonic, and neutron logs. By sonic logging, we confirmed P-wave velocity reduction that agreed fairly well with a laboratory measurement on drilled core samples from the Nagaoka site. We successfully matched the history changes of sonic P-wave velocity and estimated $CO_2$ saturation a(ter breakthrough in two observation wells out of three. The sonic-velocity history matching result suggested that the sweep efficiency was about 40%. Small effects of $CO_2$ saturation on resistivity resulted in small changes in induction logs when the reservoir was partially saturated. We also found that $CO_2$ saturation in the $CO_2$-bearing zone responded to suspension of $CO_2$ injection.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.6B
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• pp.697-707
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• 2008

The grid-based KIneMatic wave STOrm Runoff Model (KIMSTORM) by Kim (1998) predicts the temporal variation and spatial distribution of overland flow, subsurface flow and stream flow in a watershed. The model programmed with C++ language on Unix operating system adopts single flowpath algorithm for water balance simulation of flow at each grid element. In this study, we attempted to improve the model by converting the code into FORTRAN 90 on MS Windows operating system and named as ModKIMSTORM. The improved functions are the addition of GAML (Green-Ampt & Mein-Larson) infiltration model, control of paddy runoff rate by flow depth and Manning's roughness coefficient, addition of baseflow layer, treatment of both spatial and point rainfall data, development of the pre- and post-processor, and development of automatic model evaluation function using five evaluation criteria (Pearson's coefficient of determination, Nash and Sutcliffe model efficiency, the deviation of runoff volume, relative error of the peak runoff rate, and absolute error of the time to peak runoff). The modified model adopts Shell Sort algorithm to enhance the computational performance. Input data formats are accepted as raster and MS Excel, and model outputs viz. soil moisture, discharge, flow depth and velocity are generated as BSQ, ASCII grid, binary grid and raster formats.