• Journal of the Korean GEO-environmental Society
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• v.7 no.1
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• pp.55-66
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• 2006

Laboratory tests have revealed that the liquefaction resistance of sands depends strongly upon the degree of saturation, which is expressed in terms of the pore pressure coefficient, B. The velocity of compression waves(i.e. P-waves), which have been known to be influenced largely by the degree of saturation and can be measured conveniently in the field, appears as an indicator of saturation. In this paper, the Stokoe type torsional shear(TS) testing equipment is modified to saturate the specimen and measure the velocities of P-wave and S-wave and pore pressure buildup. The velocities of P-wave and S-wave for Toyoura sand from Japan is measured and compared at the various B-value (degree of saturation) which are partially saturated to fully saturated conditions. Additionally, the variation of the pore water pressure induced during undrained TS tests at the various B-value is measured and analyzed.

• Journal of the Korean Geotechnical Society
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• v.28 no.8
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• pp.55-63
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• 2012

The evaluation of shear modulus (or shear wave velocity) profile of the site is very important in various fields of geotechnical engineering and various surface wave methods have applied to determine the shear wave velocity profiles and showed good performance. Surface wave methods evaluate the dispersion curve in the field and determine the shear wave velocity profile through the inversion process. In this paper, the automated inversion process using the genetic algorithm is developed for HWAW method which is one of surface wave methods recently developed. The proposed method uses the error function based on the wavelength domain dispersion curve and can determine the reliable shear wave velocity profile not only in shallow depth but also in deep depth. To estimate the validity of the proposed method, numerical simulations and field test were performed and the proposed method was applied to determine the shear wave velocity profiles. Through the numerical simulations and field applications, the promising potential of the proposed method was verified.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.3
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• pp.502-509
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• 2001

In this paper, when stress waves are propagated along the reinforced direction of the composite, the characteristic equation of Rayleigh wave is derived. The relationships between velocities of stress waves and Rayleigh wave are studied for anisotropic ratios(E(sub)11/E(sub)12 or E(sub)22/E(sub)11). The increments of anisotropic ratios is made by using known material properties and being constant of basic properties. When the anisotropic ratios are increased, Rayleigh wave velocities to the shear wave velocities are almost equal to 1 with any anisotropic ratios. Rayleigh wave velocities to the longitudinal wave velocities and Shear wave velocities ratio to the longitudinal wave velocities are almost identical each other, they are between 0.12 and 0.21. When the anisotropic ration is very high, that is, E(sub)11/E(sub)22=46.88, Rayleigh wave velocities and the shear wave velocities are almost constant with Poissons ratio, longitudinal wave velocities are very slowly increased with the increments of Poissons ratios. When E(sub)11(elastic modulus of the reinforced direction)and ν(sub)12 are constant, Rayleigh wave velocities and the shear wave velocities are steeply decreased with the increments of anisotropic ratios and the velocities of longitudinal wave are almost constant with them. When E(sub)22(elastic modulus of the normal direction to the fiber) and ν(sub)12 are constant, Rayeigh wave velocities is slowly increased with the increments of anisotropic ratios, the shear wave velocities are almost constant with them, the longitudinal wave velocities are steeply increased with them.

• Journal of the Korean earth science society
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• v.21 no.6
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• pp.675-682
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• 2000

25 seismic shot gathers were obtained to study the two dimensional subsurface shear wave velocities in a landfilled area near the Keum river estuary. Borehole(BH#1 and BH#2) tests at two sites were made in the same area. Standard Penetration Tests were also performed at the same time. The 2-D shear wave velocity structure resulted from the inversion of the seismic data shows that the subsurface of the studied area consists of the upper 1${\sim}$3 meter thick layer(200 m/sec${\sim}$700 m/sec), the middle 5${\sim}$8 m thick low velocity layer(100 m/sec${\sim}$400 m/sec), and the lower layer of 1000m/sec or higher shear wave velocities. The thickness of the low velocity layer decreases from the BH #1 site to the BH #2 site. The depth to the basement also decreases toward the BH #2 site. The examination of the S wave velocity structure, the description of the geologic contents, and the Standard Penetration Test values indicate that the middle layer of low shear wave velocity may be related to the clay content of the layer. On the other hand, the Standard Penetration test values increase with depth, showing no significant relationship with the geologic contents of the subsurface. This study shows that the inversion of surface waves can be effective in the study of the shear wave velocity, especially in the area where low velocity layers can be found. The method of inversion of surface waves also can be used as a viable technique to overcome the limit of the seismic refraction method.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.5D
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• pp.483-492
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• 2012

The early setting time of concrete is an important factor determining the slip up velocity of the slip-form system. Accordingly, need is for a technique evaluating the early setting time in order to secure the safety of the slip-form system and the construction quality of concrete. This paper intends to estimate the early setting time by evaluating the setting degree of concrete using surface wave velocity so as to determine the slip up time of the slip-form system. Penetration resistance test and compressive strength test are performed first to clarify the relationship between the early setting time of concrete and the compressive strength. Then, compressive strength test and ultrasonic wave test are conducted to examine the relation between the compressive strength and the surface wave velocity. Continuous wavelet transform is adopted to measure the surface wave velocity. Numerical analysis is carried out to demonstrate the appropriateness of the application of continuous wavelet transform. Based on these results, the propagation velocity of the surface wave required for the slip up of slip-form system is suggested. Finally, a reduced model test of the slip-form system is conducted to verify the feasibility of the proposed surface wave velocity for the determination of th slip up velocity.

• The Journal of Engineering Geology
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• v.23 no.4
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• pp.511-517
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• 2013

The Field Velocity Probe (FVP) has been widely applied to determine the various characteristics of soils. This study seeks to estimate soil consolidation characteristics using an FVP and to increase its application in the field. The specimens were extracted from depths of 3 and 6 m at the study site, an area of soft clay in Incheon. In laboratory testing, the specimens were placed in an improved oedometer cell to measure shear wave velocity, and statistical analysis was performed to compare the results of effective stress and shear wave velocity. FVP enables increased resolution in the field because it measures the shear wave velocity every 20 cm. To estimate the condition of consolidation, we compared the results of shear wave velocities between those obtained in the laboratory and those in the field. The field conditions are used to analyze overconsolidated and normally consolidated soils at depths of 3 and 6 m, respectively. The results show that FVP is a suitable method for estimating the degree of consolidation.

• Proceedings of the Korean Geotechical Society Conference
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• 1997.10a
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• pp.261-266
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• 1997

• 한국지구물리탐사학회:학술대회논문집
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• 2005.05a
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• pp.157-164
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• 2005

Urban conditions such as underground facilities and ambient noises due to cultural activity restrict the application of conventional geophysical techniques in general. We used the refraction microtremor (REMI) technique as an alternative way to get the geotechnical information, in particular shear-wave (S-wave) velocity information, at a site along an existing rail road. The REMI method uses ambient noises recorded using standard refraction equipment to derived shear-wave velocity information at a site. It does a wavefield transformation on the recorded wavefield to produce Rayleigh wave dispersion curve, which are then picked and modeled to get the shear-wave velocity structure. At this site the vibrations from the running trains provided strong noise sources that allowed REMI to be very effective. REMI was performed along the planned new underground rail tunnel. In addition, Suspension PS logging (SPS) were carried out at selected boreholes along the profile in order to draw out the quantitative relation between the shear wave velocity from the PS logging and the rock mass rating (RMR) determined from the inspection of the cores recovered from the same boreholes, These correlations were then used to relate the shear-wave velocity derived from REMI to RMR along the entire profile. The correlation between shear wave velocity and RMR was very good and so it was possible to estimate the RMR of the total zone of interest for the design of underground tunnel,

• Korean Journal of Remote Sensing
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• v.27 no.3
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• pp.213-223
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• 2011

The purpose of this study is to estimate the spherical wave parameters that appears in synthetic aperture radar (SAR) image acquired over the coast of Chukk, Micronesia. The retrieval of ocean wave parameters consists of two main stages: the first is to determine the dominant wavelengths by Fast Fourier Transform (FFT) over 16 sub-image areas and the second is to estimate wave slopes and heights using dispersion relationship under various water wave conditions. It is assumed that the spherical waves are linear and progressive. These type of waves have the range and azimuth components traveling in radial directions. The azimuth travelling waves are more affected by the velocity bunching mechanism and it is difficult to estimate the wave parameters for these affected areas in SAR imagery. In order to compensate these effects, the velocity bunching ratio (VBR) based on modulation transfer function (MTF) was compared with the intensity ratio for neighbor area in the radial direction in order to assign the spherical wave properties for azimuthally travelling waves. Dispersion relation provides the good estimates for the wave heights for all the selected sub-image areas in the range of 1m to 2m. VBR based on MTF was found to be 0.78 at wave height of 1.36m, while the intensity-based VBR was 0.69 which corresponds to the height of 1.75m. It can be said that the velocity bunching accounts for azimuthally travelling spherical waves and the difference results from the sea-bottom effects.

• Journal of Acupuncture Research
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• v.28 no.2
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• pp.97-105
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• 2011

Objectives : The aim of this experiment is to know the effect of mountain cultivated ginseng pharmacopuncture on heart rate variability(HRV), pulse wave velocity(PWV) in middle aged women. Methods : We investigated on 20 healthy Middle Aged women volunteers. First, we measured their heart rate variability(HRV), pulse wave velocity(PWV) and then mountain cultivated ginseng pharmacopuncture 20cc were injected on them. After 30 minutes, we measured heart rate variability(HRV), pulse wave velocity(PWV) again. As a result, method of one-group pretest-posttes design were used for evaluation. Results : 1. In HRV, MeanHRV is significantly decreased from 69.15 to 63.34 after injection. 2. MeanRR is significantly increased from 877.20 to 962.10 after injection. SDNN is significantly increased from 32.56 to 41.34 after injection. 3. PNN50 is significantly decreased after injection. RNSSD, SDSD, TP, VLF is significantly increased after injection. 4. Stress resistance ability is significantly increased from 37.55 to 44.60 after injection. 5. In PWV, E-R, E-L, H-R, H-L is significantly decreased after injection. Conclusions : Effect of mountain cultivated ginseng pharmacopuncture on heart rate variability(HRV) increased adaptability of autonomic nervous system and on pulse wave velocity(PWV) decreased arterial stiffness.