• Journal of the Korean Geotechnical Society
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• v.24 no.5
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• pp.79-87
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• 2008

Recently, a new seismic probe, called "MudFork", has been developed and can be utilized for accurate and easy measurements of shear wave velocities of cohesive soils. To expand its use to estimate undrained shear strength and density, a preliminary investigation to correlate these properties with shear wave velocity was attempted. Cone penetration tests and a seismic test, using MudFork, were performed at a silty soil site near Incheon, Korea. Also, undisturbed samples were obtained using thin-wall tube samplers, and the shear wave velocities and undrained shear strengths of the samples were measured in the laboratory. A simple linear relationship between shear strength and shear wave velocity was obtained, and a tentative relationship between density and shear wave velocity was also defined.

• Journal of the Korean Geotechnical Society
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• v.33 no.4
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• pp.17-24
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• 2017

Shear wave velocity (or shear modulus) of rock filled zone of CFRD is very important factor in the evaluation of performance of CFRD under the load such as earthquake. A shear wave velocity profile can be determined by surface wave method but this profile has been uncertainty caused by spatial variation of material property in rock filled zone. This uncertainty in shear wave velocity profile could be evaluated by the reliability based analysis which uses a coefficient of variation of material property to consider uncertainty caused by spatial variation of material property. In this paper, the possible 600 shear wave velocity profiles in rock filled zone of CFRD were generated using the method based on harmonic wavelet transform and 8 shear wave velocity profiles by HWAW method in the field, and the coefficients of variation of shear wave velocity with depth were evaluated for the rock filled zone of CFRD in Korea.

• Journal of Korean Tunnelling and Underground Space Association
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• v.16 no.2
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• pp.225-236
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• 2014

Shear wave velocity was used to estimate the geotechnical characteristics (void ratio and shear strength) of ground near an underground rainfall storage facility. An oedometer cell was utilized to measure the shear wave velocity and the displacement of specimens. Shear strengths were obtained by direct shear tests. The relationships along the shear wave velocity, void ratio, and shear strength were verified and used to infer the shear strength profile with the depth. In addition, changes in shear strength due to the construction of the underground rainfall storage system were estimated using the suggested method. The results show that the in-situ shear strength deduced from the shear wave velocity-void ratio-shear strength relationship is in good agreement with that obtained from an in-situ investigation (SPT).

• The Journal of the Acoustical Society of Korea
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• v.31 no.6
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• pp.399-409
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• 2012

In this paper we propose a method for measuring the shear modulus of an ultrasound soft tissue phantom using an acoustic radiation force. The proposed method quantitatively determines the shear modulus based on the rise time of a displacement induced by an acoustic radiation force at the focal point of a focused ultrasound beam. The shear wave speed and shear modulus obtained from the proposed method and a shear wave propagation method were compared to verify the validity of the proposed method. In the shear wave propagation method, the shear modulus is first computed by measuring the propagating speed of a shear wave induced in a phantom by a limited-diffraction transmit field, and then was compared to that obtained with the proposed method in an ultrasound data acquisition system calibrated based on the first computed shear modulus. The relative errors between the two methods were found to be 4% for shear wave speed and less than 9% for shear modulus, confirming the usefulness of the proposed method.

• Structural Engineering and Mechanics
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• v.82 no.4
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• pp.491-502
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• 2022

A model experiment with a scale of 1:150 has been conducted to investigate the dynamic responses of a freestanding four-column bridge tower subjected to regular wave, random wave and coupled wave-current actions. The base shear forces of the caisson foundation and the dynamic behaviors of the superstructure were measured and analyzed. The comparisons of the test values with the theoretical values shows that wave-induced base shear forces on the bridge caisson foundation can be approximated by using a wave force calculation method in which the structure is assumed to be fixed and rigid. Although the mean square errors of the base shear forces excited by joint random wave and current actions are approximately equal to those excited by pure random waves, the existence of a forward current increases the forward base shear forces and decreases the backward base shear forces. The tower top displacements excited by wave-currents are similar to those excited by waves, suggesting that a current does not significantly affect the dynamic responses of the superstructure of the bridge tower. The experiment results can be used as a reference for similar engineering design.

• Geomechanics and Engineering
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• v.30 no.5
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• pp.449-460
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• 2022

Safe underground construction in a rock mass requires adequate ground investigation and effective determination of rock conditions. The estimation of rock mass behavior is difficult, because rock masses are innately anisotropic and heterogeneous at different scales and are affected by various environmental factors. Quantitative rock mass classification systems, such as the Q-system and rock mass rating, are widely used for characterization and engineering design. The measurement of rock classification parameters is subjective and can vary among observers, resulting in questionable accuracy. Geophysical investigation methods, such as seismic surveys, have also been used for ground characterization. Torsional shear wave propagation characteristics in cylindrical rods are equal to that in an infinite media. A probabilistic quantitative relationship between the Q-value and shear wave velocity is thus investigated considering long-wavelength wave propagation in equivalent continuum jointed rock masses. Individual Q-system parameters are correlated with stress-dependent shear wave velocities in jointed rocks using experimental and numerical methods. The relationship between the Q-value and the shear wave velocity is normalized using a defined reference condition. This relationship is further improved using probabilistic analysis to remove unrealistic data and to suggest a range of Q-values for a given wave velocity. The proposed probabilistic Q-value estimation is then compared with field measurements and cross-hole seismic test data to verify its applicability.

• YAKHAK HOEJI
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• v.59 no.4
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• pp.158-163
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• 2015

Cardiac myocytes are subjected to fluid shear stress during each contraction and relaxation. Under pathological conditions, such as valve disease, heart failure or hypertension, shear stress in cardiac chamber increases due to high blood volume and pressure. The shear stress induces proarrhythmic longitudinal global $Ca^{2+}$ waves in atrial myocytes. In the present study, we further explored underlying cellular mechanism for the shear stress-induced longitudinal global $Ca^{2+}$ wave in isolated rat atrial myocytes. A shear stress of ${\sim}16dyn/cm^2$ was applied onto entire single myocyte using pressurized fluid puffing. Confocal $Ca^{2+}$ imaging was performed to measure local and global $Ca^{2+}$ signals. Shear stress elicited longitudinally propagating global $Ca^{2+}$ wave (${\sim}80{\mu}m/s$). The occurrence of shear stress-induced atrial $Ca^{2+}$ wave was eliminated by the inhibition of ryanodine receptors (RyRs) or inositol 1,4,5-trisphosphate receptors ($IP_3Rs$). In addition, pretreatment of phospholipase C (PLC) inhibitor U73122, but not its inactive analogue U73343, abolished the generation of longitudinal $Ca^{2+}$ wave under shear stress. Our data suggest that shear-induced longitudinal $Ca^{2+}$ wave may be induced by $Ca^{2+}$-induced $Ca^{2+}$ release through the RyRs which is triggered by $PLC-IP_3R$ signaling in atrial myocytes.

• 한국지구물리탐사학회:학술대회논문집
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• 2007.06a
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• pp.7-23
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• 2007

The shear wave velocity is directly related to the deformation characteristic of soils which is an engineering property represented by the shear modulus. This feature presents an opportunity of advantageous utilization of the shear wave velocity for deformation analysis in geotechnical engineering applications, since the deformation modulus is determined on strong theoretical basis, whereas penetration resistances such as N by SPT or qc by CPT rely on empirical relations. Furthermore, it is an engineering property that can be evaluated by performing the same basic measurement in the laboratory and field, and various problems in geotechnical engineering can be dealt with economically and reliably when the field and laboratory methods are combined effectively. In this article, assessment of nonlinear deformation characteristic of soils based on synergic use of the field and laboratory test results is described, and representative case histories of geotechnical applications of the shear wave velocity are illustrated.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.03a
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• pp.255-264
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• 2009

Soils containing vanishing materials lead changes in the microstructure of particulate media due to water inflow. Thus, dissolution renders some local unstability. As the moisture contents decease, the component of the vanished materials may affects on the cementation of paniculate materials. This cementation phenomenon has a huge influence on the stiffness, strength and stability under lower stress level. The goal of this study is to introduce the cementation effects on a compressional wave velocity, a shear wave velocity, and the resonant frequency of shear waves. The glass bead and salt water with different mole contents are used. Test results show that the changes of shear and compressional wave velocities consist of three stages. In the first region, compressional wave velocities increase and shear wave velocities decrease with a decreases in reducing water contents from 100% to 90~95%. In the second region, shear and compressional wave velocities become stable at 90~95% to 10% of the water contents. In the third region, shear and compressional wave velocities increases dramatically with a decrease in the water content due to the capillary force and cementation of salt. Furthermore, the resonant frequency of the shear waves shows similar phenomenon. Specimens prepared by glass beads and salt water are proved to be able to provide a meaningful insight in under structural behaviors of the cementation.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.12
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• pp.3369-3376
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• 1994

A finite element program for elastic stress wave propagation is developed in order to investigate the shape of stress field and analysis the magnitude of stress wave intensity at time increment. Accuracy and reliance of the finite element analysis are acquired when the element size is smaller than the product of the stress wave speed and the critical value of increasing time step. In the finite element analysis and theoretical solution, the longitudinal stress wave is propagated to the similar direction of impact load, and the stress wave intensity is expressed in terms of the ratio of propagated area. The direction of shear wave is declined at an angle of 45 degrees compared with longitudinal stress wave and the speed of shear wave is half of the longitudinal stress wave.