• Title/Summary/Keyword: Triaxial Test

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An Experimental Study on Dynamic Deformation Properties of Rock Materials using Large Triaxial Testing Apparatus (대형진동삼축시험기를 이용한 암석재료의 동적변형특성에 관한 실험적 연구)

  • 신동훈
    • Proceedings of the Korean Geotechical Society Conference
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    • 2003.03a
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    • pp.299-308
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    • 2003
  • In order to investigate the dynamic deformation properties of rockfill materials in small strain level, cyclic triaxial tests were conducted using the large cyclic triaxial testing apparatus, which was developed by Water Resources Research Institute of KOWACO in 2001. Two types of rockfill materials consisting of granite and shale-sandstone were tested in this study. The test results show that G/G$\_$max/ of granite specimen decreases more than that of shale-sandstone with the increase of shear strain and the increase ratio in the maximum shear modulus G$\_$max/ of granite is bigger than the ratio of shale-sandstone.

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The new approach to calculate pulse wave returning energy vs. mechanical energy of rock specimen in triaxial test

  • Heidari, Mojtaba;Ajalloeian, Rassoul;Fard, Akbar Ghazi;Isfahanian, Mahmoud Hashemi
    • Geomechanics and Engineering
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    • v.25 no.3
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    • pp.253-266
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    • 2021
  • In this paper, we discuss a mathematical method for determining the return energy of the wave from the sample and comparing it with the mechanical energy consumed to change the dimension of the sample in the triaxial test of the rock. We represent a method to determine the mechanical energy and then we provide how to calculate the return energy of the wave. However, the static energy and pulse return energy will show higher amounts with axial pressure increase. Three types of clastic sedimentary rocks including sandstone, pyroclastic rock, and argillitic tuff were selected. The sandstone showed the highest strength, Young's modulus and ultrasonic P and S waves' velocities versus others in the triaxial test. Also, from the received P wavelet, the calculated pulse wave returning energy indicated the best correlation between axial stress compared to wave velocities in all specimens. The fact that the return energy decreases or increases is related to increasing lateral stress and depends on the geological characteristics of the rock. This method can be used to determine the stresses on the rock as well as its in-situ modulus in projects that are located at high depths of the earth.

A Study on the Characteristics of Shear Strength in Unsaturated Cohesive Soils (불포화 점성토의 전단강도 특성에 관한 연구)

  • 유범식;조덕현
    • Magazine of the Korean Society of Agricultural Engineers
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    • v.23 no.3
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    • pp.96-104
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    • 1981
  • In order to investigate the characteristics of the shear strength of the unsaturated cohesive soils which has mean characters of sand and clay widely used for banking, I selected soil samples from An-sung district and, against it, performed direct shear test and unconfined compression test changing grain size, compaction energy and moisture content and also performed triaxial compression test under optimum moisture content. The results are as follows; 1.As the passing percent of the No. 200 sieve increased from 23.6% to 56.1%, cohesion increased from 0. 202kg/cm2 to 0. 398kg/cm2 under the direct shear test and from 0.38 kg/cm2 to 1. 05kg/cm2 under the tria4al compression test, internal friction angle decreased from 44. 78$^{\circ}$ to 34. 34$^{\circ}$ under the direct shear test and from 31. 88$^{\circ}$ to 13. 31$^{\circ}$ under the triaxial compression test. 2.Cohesion showed it's maximum value around OMC and internal friction angle showed a tendency to increase according to the decrease of water content but it's increasing ratio was relatively slow. 3.Decreasing ratio of cohesion and internal friction angle was relatively sensitive according to the decrease of compaction energy. 4.The smaller of the vertical stress and the coarser of the grain size of samples, changing of the volume showed a tendency to increase and as the increase of water content, the shear displacement (dh) at failure shear stress ($\tau$f) showed maximum and the $\tau$f-dh curve was gentle. 5.To synthesize the results of the direct shear test and the triaxial compression test, cohesion showed higher under the triaxial compression test and internal friction angle showed a tendeney to appear higher under the direct shear test. It seems that we can get correspondent results by removing the side friction of mold with soils and adjusting the vertical stress and shearing speed under the direct shear test.

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Dynamic Deformation Characteristics of Joomunjin Standard Sand Using Cyclic Triaxial Test (반복삼축압축시험을 이용한 주문진 표준사의 동적변형특성 분석)

  • Kim, You-Seong;Ko, Hyoung-Woo;Kim, Jae-Hong;Lee, Jin-Gwang
    • Journal of the Korean Geotechnical Society
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    • v.28 no.12
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    • pp.53-64
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    • 2012
  • In this study, the modified cyclic triaxial tests with Joomunjin standard sand are performed for dynamic deformation characteristics, such as Young's moduli and damping ratio. The cyclic triaxial test is equipped with Local Displacement Transducer (LDT) on the outside of a cell which has a range from $10^{-4}$ to $10^{-1}$ of shear strains, ${\gamma}$ (%), instead of conventional cyclic triaxial test which has linear variable displacement transducer (LVDT) with low precision. With the small strain control, tests were carried out at various loading rates, void ratios, and effective confining pressures. Based on the test results, such as dynamic deformation characteristics, shear modulus, and damping ratio, it is found that the test can measure more range of medium strains (0.02-0.2%) than results obtained from conventional test (resonant column test). For the medium strain range, dynamic deformation characteristics investigated by the cyclic triaxial test are also different from those predicted by nonlinear model in conventional test.

Evaluation of the q-w Curve on Rock-Socketed Drilled Shafts by Triaxial Compression Tests (삼축압축시험을 통한 암반에 근입된 현장타설말뚝의 선단 하중전이곡선 산정)

  • Kim, Tae-Hyung;Kim, Yong-Min;Jeong, Sang-Seom
    • Proceedings of the Korean Geotechical Society Conference
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    • 2008.10a
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    • pp.455-465
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    • 2008
  • In this study, the load distribution and deformation of rock-socketed drilled shafts subjected to axial load are investigated based on small scale model tests. In order to analyze the effects of major influencing factors of end bearing capacity, Hoek-cell triaxial tests were performed. From the test results, it was found that the initial slope of end bearing load transfer (q-w) curve was highly dependent on rock mass modulus and pile diameter, while the ultimate unit toe resistance ($q_{max}$) was influenced by rock mass modulus and the spacing of discontinuities. End bearing load transfer function of drilled shafts socketed in rock was proposed based on the Hoek-cell triaxial test results and the field loading tests which were performed on granite and gneiss in South Korea. Through the comparison with pile load tests, it is found that the load-transfer curve by the present study is in good agreement with the general trend observed by field loading tests, and thus represents a significant improvement in the prediction of load transfer of drilled shaft.

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A simple creep constitutive model for soft clays based on volumetric strain characteristics

  • Chen, G.;Zhu, J.G.;Chen, Z.;Guo, W.L.
    • Geomechanics and Engineering
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    • v.29 no.6
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    • pp.615-626
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    • 2022
  • The soft clays are widely distributed, and one of the prominent engineering problems is the creep behavior. In order to predict the creep deformation of soft clays in an easier and more acceptable way, a simple creep constitutive model has been proposed in this paper. Firstly, the triaxial creep test data indicated that, the strain-time (𝜀-t) curve showing in the 𝜀-lgt space can be divided into two lines with different slopes, and the time referring to the demarcation point is named as tEOP. Thereafter, the strain increments occurred after the time tEOP are totally assumed to be the creep components, and the elastic and plastic strains had occurred before tEOP. A hyperbolic equation expressing the relationship between creep volumetric strain, stress and time is proposed, with several triaxial creep test data of soft clays verifying the applicability. Additionally, the creep flow law is suggested to be similar with the plastic flow law of the modified Cam-Clay model, and the proposed volumetric strain equation is used to deduced the scaling factor for creep strains. Therefore, a creep constitutive model is thereby established, and verified by successfully predicting the creep principal strains of triaxial specimens.

Shearing characteristics of slip zone soils and strain localization analysis of a landslide

  • Liu, Dong;Chen, Xiaoping
    • Geomechanics and Engineering
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    • v.8 no.1
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    • pp.33-52
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    • 2015
  • Based on the Mohr-Coulomb failure criterion, a gradient-dependent plastic model that considers the strain-softening behavior is presented in this study. Both triaxial shear tests on conventional specimen and precut-specimen, which were obtained from an ancient landslide, are performed to plot the post-peak stress-strain entire-process curves. According to the test results of the soil strength, which reduces from peak to residual strength, the Mohr-Coulomb criterion that considers strain-softening under gradient plastic theory is deduced, where strength reduction depends on the hardening parameter and the Laplacian thereof. The validity of the model is evaluated by the simulation of the results of triaxial shear test, and the computed and measured curves are consistent and independent of the adopted mesh. Finally, a progressive failure of the ancient landslide, which was triggered by slide of the toe, is simulated using this model, and the effects of the strain-softening process on the landslide stability are discussed.

A Behavior of Clayey Foundation Using Elasto-plastic Constitutive Model - On the Lade's Model, Cubical Triaxial Test and the Determination of Soil Parameters- (탄.소성구성식에 의한 점토지반의 거동해석 (I) -Lade의 모델, 입방체 삼축시험 및 토질매개변수 결정-)

  • 이문수;이광동;오재화
    • Magazine of the Korean Society of Agricultural Engineers
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    • v.35 no.4
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    • pp.106-118
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    • 1993
  • The purpose of this study is to develop a multireservoir water balance model which may be used to evaluate rural water demands such as agricultural water, domestic water, industrial water and livestock water and to determine effective storage of reservoir. The model was verified to compare the observed reservoir release data with the simulated reservoir release data of the existing Munsan and Dongbu reservoirs located in the Gisan rural district for 3 years('87~'89). For model application, the effective storages of existing reservoirs(Munsan & Dongbu) were evaluated for 10-year frequency drought and that of newly planned reservoirs(Kumbok & Kudong) were determined for 10-year frequency drought. In addition, the behavior of effective storages for existing reservoirs were analyzed in the case of introducing new reservoirs in the existing system.

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Frequency Dependence in Large Strain Range During Cyclic Triaxial Tests of Clay (점성토의 진동삼축시험시 대변형률영역에서의 주파수 의존성)

  • Kim, Yong-Seong
    • Journal of The Korean Society of Agricultural Engineers
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    • v.48 no.5
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    • pp.63-71
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    • 2006
  • In the present study, the dynamic deformation characteristics of clay, including the effect of loading rate in large strain ranges, were examined by performing undrained cyclic triaxial test. The test results showed that the loading rate to failure decreased with increasing loading amplitude and decreasing loading frequency. While the stress-strain relationships was not affected by loading frequency, excess pore pressure was affected significantly with the change in loading frequency. The change for 0.1 Hz was larger for than that of 0.01 Hz, resulting in inclined effective stress paths. Furthermore, the lower the frequency was, the higher the excess pore pressure was in the first loading.

Study on Plastic Deformation of Cohesionless Soil through Cyclic Triaxial Test (반복삼축압축실험을 통한 사질토의 소성변형 특성에 관한 연구)

  • Shin, Eun-Chul;Kang, Hyoun-Hoi;Choi, Chan-Young;Yang, Hee-Aaeng
    • Proceedings of the Korean Geotechical Society Conference
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    • 2008.10a
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    • pp.1370-1376
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    • 2008
  • The structure of railroad or subway is that low fare transportation system of the large traffic volume. Like this structure is subjected to the cyclic load of moving vehicle. Consequently the result of the settlement analysis or plastic deformation prediction of railroad bed could be used as an important factor in safety of the railroad. The results of cyclic triaxial test were used in the numerical analysis of power model which Li and Selig(1994) developed. The soil samples were obtained from the construction site of railroad. Cyclic triaxial test was conducted with the variation of the magnitude of cyclic load and soil types. The large magnitude of plastic deformation in the railroad bed is caused of structure failure of the railroad.

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