• Title, Summary, Keyword: Shear wave velocity

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Determination of Shear Wave Velocity Profile Model Considering Uncertainty Caused by Spatial Variation of Material Property in Rockfill Zone of Fill Dam (물성치 변동성에 의한 불확실성이 고려된 국내 필댐 사력부를 위한 전단파 속도 주상도 모델)

  • Park, Hyung-Choon
    • Journal of the Korean Geotechnical Society
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    • v.35 no.2
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    • pp.29-36
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    • 2019
  • There always exist the spatial variations of material properties such as a shear wave velocity in a dam and between same type dams. These uncertainties cause those in evaluation of a shear wave velocity profile of a dam and should be considered in determining the shear wave velocity profile for a rockfill zone of a fill dam. In this paper, these uncertainties of a shear wave velocity in the rockfill zone of the fill dam in Korea are evaluated. And the shear wave velocity profile model considering these uncertainties in rockfillzone is proposed using the method based on Harmonic wavelet transform. The proposed shear wave velocity profile model is compared with Sawada-Takahashi model widely used for evaluation of a shear wave velocity profile of a rockfill zone of fill dams.

Relationship between Shear Wave Velocity, Undrained Shear Strength and Density of Normally Consolidated Silt (실트질 세립토의 전단파속도와 비배수 전단강도 및 밀도의 상관관계)

  • Park, Dong-Sun;Oh, Sang-Hoon;Mok, Young-Jin
    • Proceedings of the Korean Geotechical Society Conference
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    • pp.318-326
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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 soft soils. To expand its use to estimate undrained shear strength and density, correlations between those and shear wave velocity were being attempted. Cone penetration tests and a seismic test, using MudFork, were performed at a soft ground site near Incheon, Korea. Also, undisturbed samples were obtained and shear wave velocities of the samples were measured as well as undrained shear strength, using triaxial compression test and bender elements. 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.

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Shear Wave Velocity in Unconsolidated Marine Sediments of the Western Continental Margin, the East Sea

  • Kim, Gil-Young;Kim, Dae-Choul
    • The Journal of the Acoustical Society of Korea
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    • v.22 no.4E
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    • pp.167-175
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    • 2003
  • Shear wave velocity was measured and grain size analysis was conducted on two core samples obtained in unconsolidated marine sediments of the western continental margin, the East Sea. A pulse transmission technique based on the Hamilton frame was used to measure shear wave velocity. Duomorph ceramic bender transducer-receiver elements were used to generate and detect shear waves in sediment samples. Time delay was calculated by changing the sample length from the transducer-receiver element. Time delay is 43.18 μs and shear wave velocity (22.49 m/s) is calculated from the slope of regression line. Shear wave velocities of station 1 and 2 range from 8.9 to 19.0 m/s and from 8.8 to 22 mis, respectively. Shear wave velocities with depth in both cores are qualitatively in agreement with the compared model〔1〕, although the absolute value is different. The sediment type of two core samples is mud (mean grain size, 8-9Φ). Shear wave velocity generally increases with sediment depth, which is suggesting normally consolidated sediments. The complicated variation of velocity anisotropy with depth at station 2 is probably responsible for sediment disturbance by possible gas effect.

Relationship Between Stiffness And Shear Strength of Normally Consolidated Clays (정규압밀점토의 강성도와 전단강도의 상관관계)

  • Park, Chi-Won;Park, Dong-Sun;Mok, Young-Jin
    • Proceedings of the Korean Geotechical Society Conference
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    • pp.402-413
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    • 2006
  • Strength evaluation of soft soils is a formidable task because of difficulties in sampling, specimen preparation and setting in triaxial cells. In undrained triaxial testing, sampling disturbance, verticality of specimen and bedding effect give a great influence on shear strength measurements. In the other hand, shear wave measurements of specimens are less influenced by these factors. In this research, the bender elements were attached top cap and base pedestal of triaxial cell and shear wave velocities were measured. To initiate a methodology to evaluate shear strength indirectly by measuring shear wave velocity, a relationship between shear strength and shear wave velocity was developed with kaolinite specimens consolidated in the laboratory. Undrained shear strength turns out to increase linearly with shear wave velocity. Stress-strain curves can also be predicted with a hyperbolic model and shear wave measurements.

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Shear wave velocity of sands subject to large strain triaxial loading

  • Teachavorasinskun, Supot;Pongvithayapanu, Pulpong
    • Geomechanics and Engineering
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    • v.11 no.5
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    • pp.713-723
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    • 2016
  • Shear wave velocities of three selected sandy soils subject to drained triaxial compression test were continuously measured using the bender elements. The shear wave velocity during isotropic compression, as widely recognized, increased as confining pressure increased and they were correlated well. However, during drained shearing, the mean effective stress could no further provide a suitable correlation. The shear wave velocity during this stage was almost constant with respect to the mean effective stress. The vertical stress was found to be more favorable at this stage (since confining stress was kept constant). When sample was attained its peak stress, the shear wave velocity reduced and deviated from the previously existed trend line. This was probably caused by the non-uniformity induced by the formation of shear band. Subsequently, void ratios computed based on external measurements could not provide reasonable fitting to the initial stage of post-peak shear wave velocity. At very large strain levels after shear band formation, the digital images revealed that sample may internally re-arrange itself to be in a more uniform loose stage. This final stage void ratio estimated based on the proposed correlation derived during pre-peak state was close to the value of the maximum void ratio.

Evaluation of preconsolidation stress by shear wave velocity

  • Yoon, Hyung-Koo;Lee, Changho;Kim, Hyun-Ki;Lee, Jong-Sub
    • Smart Structures and Systems
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    • v.7 no.4
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    • pp.275-287
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    • 2011
  • The behaviors of saturated soils such as compressibility and permeability are distinguished by preconsolidation stress. Preconsolidation stress becomes an important design parameter in geotechnical structures. The goal of this study is to introduce a new method for the evaluation of preconsolidation stress based on the shear wave velocity at small strain, using Busan, Incheon, and Gwangyang clays in Korea. Standard consolidation tests are conducted by using an oedometer cell equipped with bender elements. The preconsolidation stresses estimated by shear wave velocity are compared with those evaluated by the Casagrande, constrained modulus, work, and logarithmic methods. The preconsolidation stresses estimated by the shear wave velocity produce very similar values to those evaluated by the Onitsuka method (one of the logarithmic methods), which yields an almost real preconsolidation stress. This study shows that the shear wave velocity method provides a reliable method for evaluating preconsolidation stress and can be used as a complementary method.

Characteristics of Shear Wave Velocity as Stress-Induced and Inherent Anisoptopies (응력유도 및 고유 이방성에 따른 전단파 속도 특성)

  • Lee, Chang-Ho;Lee, Jong-Sub;Cho, Tae-Hyeon;Lee, Jeong-Hark;Kim, Sang-Ho
    • Proceedings of the Korean Geotechical Society Conference
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    • pp.137-146
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    • 2006
  • Shear wave velocity of uncemented soil can be expressed as the function of effective stresses when capillary phenomenons are negligible. However, the terms of effective stresses are divided to the direction of wave propagation and polarization because stress states are generally anisotropy. The shear wave velocities are affected by parameters and exponents that are experimentally determined. The exponents are controlled contact effects of particulate materials(sizes, shapes, and structures of particles) and the parameters are changed contact behaviors between particles, material properties of particles, and type of packing(i.e., void ratio and coordination number). In this study, consolidation tests are performed by using clay, mica and sand specimens. Shear wave velocities are measured during consolidation tests to investigate the stress-induced and inherent anisotropies through bender elements. Results show the shear wave velocities depends on the stress-induced anisotropy for round particles. Furthermore the shear wave velocity is dependent on particle alignment under the constant effective stress. This study suggests that the shear wave velocity and the shear modulus should be carefully calculated and used for the design and construction of geotechnical structures.

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An experimental procedure for evaluating the consolidation state of marine clay deposits using shear wave velocity

  • Chang, Ilhan;Kwon, Tae-Hyuk;Cho, Gye-Chun
    • Smart Structures and Systems
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    • v.7 no.4
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    • pp.289-302
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    • 2011
  • In marine clay deposits, naturally formed or artificially reclaimed, the evaluation and monitoring of the consolidation process has been a critical issue in civil engineering practices due to the time frame required for completing the consolidation process, which range from several days to several years. While complementing the conventional iconographic method suggested by Casagrande and recently developed in-situ techniques that measure the shear wave, this study suggests an alternative experimental procedure that can be used to evaluate the consolidation state of marine clay deposits using the shear wave velocity. A laboratory consolidation testing apparatus was implemented with bimorph-type piezoelectric bender elements to determine the effective stress-shear wave velocity (${\sigma}^{\prime}-V_s$) relationship with the marine clays of interest. The in-situ consolidation state was then evaluated by comparing the in-situ shear wave velocity data with the effective stress-shear wave velocity relationships obtained from laboratory experiments. The suggested methodology was applied and verified at three different sites in South Korea, i.e., a foreshore site in Incheon, a submarine deposit in Busan, and an estuary delta deposit in Busan. It is found that the shear wave-based experimental procedure presented in this paper can be effectively and reliably used to evaluate the consolidation state of marine clay deposits.

Study on Shear Wave Velocity of Fill Dam Core zone using Surface Wave Method (표면파탐사에 의한 필댐 코어죤의 전단파속도 연구)

  • Kwon, Hyek-Kee;Shin, Eun-Chul
    • Proceedings of the Korean Geotechical Society Conference
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    • pp.209-218
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    • 2009
  • In this study, properties of shear wave velocity of core zone in filldams are analyzed. Shear wave velocity is derived using analysis of surface wave method that can be used nondestructively on the surface of filldams. These values are acquired through the tests for the core zone of six filldams by SASW and HWAW methods. Existing 2 more results are added. Shear wave velocity according to the depth and confining pressure are estimated, respectively. These analytical results are compared with the frequently used empirical method by Sawada and Takahashi.

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Evaluation of Average Shear-wave Velocity Estimation Methods of Multi-layered Strata Considering Site Period (지반주기를 고려한 다층지반의 평균전단파속도 추정 방법 평가)

  • Kim, Dong-Kwan
    • Journal of the Earthquake Engineering Society of Korea
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    • v.23 no.3
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    • pp.191-199
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    • 2019
  • To calculate proper seismic design load and seismic design category, the exact site class for construction site is required. At present, the average shear-wave velocity for multi-layer soil deposits is calculated by the sum of shear-wave velocities without considering of vertical relationship of the strata. In this study, the transfer function for the multi-layered soil deposits was reviewed on the basis of the wave propagation theory. Also, the transfer function was accurately verified by the finite element model and the eigenvalue analysis. Three methods for site period estimation were evaluated. The sum of shear-wave velocities underestimated the average shear-wave velocities of 526 strata with large deviations. The equation of Mexican code overestimated the average shear-wave velocities. The equation of Japanese code well estimated the average shear-wave velocities with small deviation.