• The Journal of Engineering Geology
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• v.18 no.4
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• pp.371-379
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• 2008

In this study, seismic elastic wave and dynamic elastic modulus properties are investigated by down-hole seismic tests that were applied to the 11 gneiss area. The research results show that the realtionship between the two properties are $V_s=0.5589{\times}V_p$ in gneiss. The relationship between the two properties are separated into two groups. Group 1 is influenced mainly by the specific gravity of rock, but group 2 is influenced mainly by the joint aperture. As weathering progresses, group 1 clearly shows a decreasing tendency. In fresh and slightly weathered rock-mass, correlations between $V_p$ and dynamic elastic modulus is expressed in linear line but in moderately-highly weathered rock-mass, correlations between $V_p$ and dynamic elastic modulus is expressed curve as a quadratic function. Correlations between $V_s$ and dynamic elastic modulus are analyzed similar with a $V_p$ case.

• 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.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.3
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• pp.1037-1047
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• 2013

A systematic laboratory compaction testing was performed with the laboratory seismic measurements of the compacted specimens sampled from various compaction fills and was supplemented with in-situ seismic testing to investigate the effects of compaction energy on the elastic wave velocities of the railway roadbed materials. The both variances of the compressive and shear wave velocities with moisture content curve ($V_p$-w and $V_s$-w curves) are similar to the general trend of the density-moisture content curve(${\gamma}_d$-w curve). At the wet side of optimal moisture content (OMC), either $V_p$ or $V_s$ does not significantly increase, which is well reflecting the no gaining in density with the increasing compaction energy exceeding modified-D compaction effort. $V_p$ increases linearly with ${\gamma}_d$ at the dry side of OMC, while it does exponentially at the wet side. The in-situ wave velocities were found to be influenced by the level of confinement and $V_s$ was more sensitive to compaction energy than $V_p$.

• Journal of the Korean Geotechnical Society
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• v.35 no.7
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• pp.41-50
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• 2019

Gyeongju bentonite is a buffer material primarily considered in Korea and it is highly compacted as a part of an engineered barrier system (EBS) of high-level radioactive waste repository. The compacted bentonite undergoes swelling stress by groundwater penetration and thermal stress by decay heat from a canister. Therefore, the mechanical properties of the compacted bentonite buffer material is crucial for the performance assessment of EBS. This paper aims to evaluate deformation properties of Gyeongju compacted bentonite using seismic methods. Two sets of compacted bentonite specimens were prepared having dry densities of $1.59g/cm^3$ and $1.75g/cm^3$ with water contents of 10.6% and 8.7%. Free-free resonant column tests were performed to measure constrained and unconstrained compression wave velocities. With the measured wave velocities, Young's modulus ($E_{max}$) and constrained modulus ($M_{max}$), material damping ratio ($D_{min}$), and Poisson's ratio at small strain were determined. As results, this paper evaluates the deformation properties of Gyeongju compacted bentonite and compares them with the results of previous researches.

• International Journal of Highway Engineering
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• v.11 no.2
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• pp.67-74
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• 2009

The strength of concrete is one of the most important parameters in evaluating the properties of concrete. Compressive strength of concrete has been widely used because of its convenience of experiments and generality. Compressive strength of concrete varies according to materials and curing conditions. Even with the same materials, the strength varies according to the curing conditions. Therefore, if we want to know the strength of concrete from the construction field, we have to put it in exactly the same curing condition with the construction field. But it is impossible to make the exactly same curing conditions in the laboratory. Also damages occur in order to measure the strength of concrete, because the core hat to be made into the pavement. To overcome these limits, many studies of nondestructive method have already been researched. It was already proven that shear wave velocity was very closely related to the compressive strength. In this study, three different curing temperatures with the same mixture paste were used, and compressive strength and shear wave velocity, according to the aging were measured. The relationship between these two parameters was examined. As results, curing temperature affected the compressive strength and the shear wave velocity, but did not affect the relation between them.

• Journal of the Korean GEO-environmental Society
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• v.16 no.11
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• pp.5-11
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• 2015

The development of Controlled Low Strength Material (CLSM), which is a highly flowable material, has been performed for the application of backfill. The objective of this study is to compare the compressive strength and compressive wave velocity of CLSM according to the curing time. To investigate the characteristics of the CLSM consisting of sand, silt, water, flyash, and CSA cement, uniaxial compression test and flow test were carried out. For the measurement of compressional waves, a cell and a couple of transducers were used. The test results show that the compressive strength increases with the curing time, while the increment of compressive strength decreases with the curing time. In addition, the compressive wave velocity increases with the curing time, and the correlation between the compressive wave velocity and compressive strength is similar to exponential function. This study suggests that the correlation between the compressive wave velocity and compressive strength may be effectively used for the estimation of compressive strength of the CLSM at early curing time.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2011.04a
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• pp.521-524
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• 2011

본 논문에서는 순환골재에 대하여 구조용 적용성 검증을 목표로 하였으며, 천연골재와 순환골재 치환율에 따른 압축파괴강도와 압축강도증가에 따른 파속도의 상관관계를 비교 분석하였다. 설계기준강도 21, 27, 35MPa에 순환굵은골재 치환율 0, 30, 50, 100%를 적용하여 설계기준강도에 따른 순환굵은골재 치환율의 배합을 총 12가지로 설정하였다. 재령160일까지의 압축파괴강도의 변화를 대기양생 공시체, 수중 양생공시체 그리고 코어공시체를 이용하여 비교하였고, 모의부재(800${\times}$800${\times}$200mm)를 통하여 재령160일까지의 초음파속도를 측정하였다. 압축파괴실험을 통하여 취득한 데이터를 비교해 본 결과 순환굵은골재 치환율에 따른 강도저하현상은 나타나지 않았다. 또한, 재령일에 따른 강도 증가와 함께 파속도도 같이 증가함을 알 수 있었다.

• Journal of the Korean Geotechnical Society
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• v.25 no.5
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• pp.75-86
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• 2009

Salt, one of the most common soluble materials in engineering soil, may have an effect on mechanical behaviors of soils under its cementation process. In order to investigate this natural phenomenon, non-soluble material by using glass beads is mixed with salt electrolyte and cemented by using oven to evaporate water. Three different sizes of glass bead particles, 0.26, 0.5, and 1.29 mm, with different salt concentration, 0, 0.1, 0.2, 0.5, 1.0, and 2.0M, are explored by using P- and S-waves, excited by bender elements and piezo disk elemets, respectively. The velocities of the P-wave and S-wave of the particulate medium cemented by salt show three stages with the degree of saturation: 1) S-wave velocities increase while P-wave velocities reduce with degree of saturation changing from 100% to 90%; 2) Both velocities are stable with degree of saturation varying from 90% to 10%; 3) The velocities change enormously when the specimens are nearly dry with degree of saturation from 10% to 0%. Besides, the resonance frequencies of S-wave show similar stages to the S-wave velocities. This study demonstrates meaningful trends of elastic wave characteristics of geo-materials according to the cementation of dissolved salt.

• Geophysics and Geophysical Exploration
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• v.9 no.3
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• pp.193-206
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• 2006

Among various borehole seismic testing techniques for determining body wave velocity, crosshole seismic method has been known as one of the most suitable technique for evaluating reliably geotechnical dynamic properties. In this study, to perform successfully the crosshole seismic test for rock as well as soil layers regardless of the groundwater level, multi-purposed spring-loaded source which impact horizontally a subsurface ground in vertical borehole was developed and applied at major facility sites in Korea. The geotechnical dynamic properties were evaluated by determining efficiently the body wave velocities such as shear wave velocity and compressional wave velocity from the horizontally impacted crosshole seismic tests at study sites, and were provided as the fundamental parameters for the seismic performance evaluation and seismic design of the target facilities.

• International Journal of Highway Engineering
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• v.13 no.1
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• pp.169-175
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• 2011

Strength is one of the very important factors to evaluate the physical properties of concrete. Aggregate forms the most parts in concrete. Cement as a binder in concrete is also closely related to strength. This experiment was tested to understand the effect of the characteristics of aggregate and cement on the relationship between concrete compressive strength and Shear Wave velocity. It was experimented by the different types of cement and maximum coarse aggregate sizes. Type I cement and rapid setting cement was used. Aggregates from three different regions were used. Aggregate of 19mm and 13mm maximum coarse aggregate sizes was used for grading. The relationship between compressive strength and Shear Wave velocity was tested under the condition of same mixture. LA wear test was used to quantify the characteristics of aggregate. As a result, the relationship between concrete compressive strength and Shear Wave velocity was affected by the types of cement, but regular relationship was appeared regardless of types of aggregate, grading and abrasion ratio.