• Title/Summary/Keyword: Liquefaction resistance ratio

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A Study on Liquefaction Potential at Reclained Land by Hydraulic Hammer Compaction (유압햄머다짐 준설매립지반의 액상화평가에 관한 연구)

  • 김종국;김영웅;최인걸;최원호
    • Proceedings of the Korean Geotechical Society Conference
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    • 2001.03a
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    • pp.517-524
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    • 2001
  • In this study, the effect of relative density and fine contents(Finer then # 0.08mm sieve) on liquefaction phenomenon in reclaimed land by hydraulic hammer compaction is analyzed. For more site-specific studies, reclaimed land in Inchon International Airport is selected and the cyclic triaxial tests are performed on disturbed samples. In cyclic triaxial tests, the characteristics of reclaimed land in Inchon International Airport are considered sufficiently. The liquefaction resistance stress ratio ($\tau$$\ell$/$\sigma$v') can be defined by relative density 40, 50, 60, and 70% and also by fine contents : 0, 10, 20, 30, and 40% under relative density (D$\_$r/) 50% used disturbed samples. From tile result of comparing tile cyclic triaxial tests, it is shown that the liquefaction strength of soil increases with increases of relative density and fine contents. Fspecially fine contents is the main factor affecting the liquefaction potential. In addition, the liquefaction resistance stress ratio is reduced by the increase of fine content and tile ratio of change is steep until fine contents 20% and that is flexible during the range of fine contents 20% to 40%. Through this study, it is proved that the soil characteristics (fine contents 5∼20%) of the reclaimed land in Inchon International Airport flays an important role in the reduction of liquefaction potential.

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A Study on the Liquefaction Resistance of Anisotropic Sample under Real Earthquake Loading (이방 구속 조건에서 실지진 하중을 이용한 액상화 저항강도 특성 분석)

  • Lee, Chae-Jin;Jeong, Sang-Seom;Kim, Soo-Il
    • Proceedings of the Korean Geotechical Society Conference
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    • 2009.09a
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    • pp.1188-1191
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    • 2009
  • In this study, cyclic triaxial tests were performed with the samples which were anisotropically consolidated using irregular earthquake loading to consider in-situ condition and seismic wave. The consolidation pressure ratio(K) was changed from 0.5 to 1.0. The Ofunato and Hachinohe wave are applied as irregular earthquake loading and liquefaction resistance strength was estimated from excess pore water pressure(EPWP) ratio. As results of the cyclic triaxial tests, buildup of EPWP ratio increased as K value increased. It shows, that the isotropically consolidated sands is more susceptible to liquefaction than anisotropically consolidated sands under equal conditions such as confining pressure and dynamic loading.

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Occurrence of Sand Liquefaction on Static and Cyclic Loading (정적 및 동적 하중에서 모래의 액상화 발생)

  • 양재혁
    • Journal of the Korean Geotechnical Society
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    • v.17 no.6
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    • pp.235-244
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    • 2001
  • Liquefaction may be caused by sudden decrease in the soil strength under undrained conditions. This loss of soil strength is related to the development of excess pore pressures. During this study, fines content affects the maximum and minimum void ratios are investigated. The results of static and cyclic triaxial test on silty saturated sands are presented. These tests are performed to evaluate liquefaction strength and static and cyclic behavior characteristics. The samples are obtained from Saemangeum and drying on air. The main results are summarized as follows : 1) The maximum and minimum void ratio lines follow similar trends. 2) Maximum and minimum void ratios are established at 20~30% fines content. 3) As confining pressures and overconsolidation ratio are increased, the resistance to liquefaction are increased. 4) Instability friction angles are increased with increasing initial relative density. 5) The resistance to liquefaction are decreased with increasing effective stress ratio.

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Liquefaction Characteristic of Pohang Sand Based on Cyclic Triaxial Test (진동삼축시험을 통한 포항 지역 사질토의 액상화 저항 특성 연구)

  • Hwang, Byongyoun;Han, Jin-Tae;Kim, Jongkwan;Kwak, Tae-Young
    • Journal of the Korean Geotechnical Society
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    • v.36 no.9
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    • pp.21-32
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    • 2020
  • In this study, series of cyclic triaxial tests and shear velocity measurement were conducted using Pohang sand, which was taken from liquefaction observed area, to verify the liquefaction characteristics of Pohang. The cyclic resistance ratio(CRR) was derived based on the test results. A specimen was reconstituted into 40% and 80% relative density conditions and then a series of cyclic triaxial tests and shear-wave velocity measurement were conducted. As a result, the effect of particle distribution and relative density to liquefaction resistance was verified. The liquefaction resistance of Pohang sand was evaluated by comparing with other liquefaction resistance of sands from previous research. In addition, the liquefaction resistance curve from field observation data was used to verify the reliability of results from this study by measured shear-wave velocity.

Experimental Analysis of Liquefaction Resistance Characteristics of Silica Sand Used in Earthquake Simulation Tests (국내 지진 모의시험에 이용되는 규사의 액상화 저항특성에 관한 실험적 분석)

  • Choi, Jaesoon;Jin, Yunhong;Baek, Woohyun
    • Journal of the Korean GEO-environmental Society
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    • v.23 no.5
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    • pp.5-13
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    • 2022
  • In this study, dynamic characteristics and liquefaction resistance characteristics of silica sand which is used to simulate sandy layer were conducted using the cyclic triaxial test according to the relative density difference. The difference in liquefaction resistance with the relative density was confirmed through the test results, which the relative density conditions were changed to 40%, 60%, and 80%, and the cyclic resistance ratio (CRR) curve of the silica sand was obtained. In addition, in order to examine the validity of the liquefaction resistance ratio (CRR) curve, artificial silica sand ground was created, and liquefaction potential was evaluated through the simple assessment method and the detailed assessment method, and the safety factors of each were compared.

Liquefaction Behaviour of Saturated Silty Sand Under Monotonic Loading Conditions (정적하중 상태에서 포화된 실트질 모래의 액상화 거동)

  • Lee Dal-Won
    • Journal of The Korean Society of Agricultural Engineers
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    • v.48 no.4
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    • pp.67-74
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    • 2006
  • This study was carried out to investigate the liquefaction behaviour of saturated silty sand under monotonic loading conditions. The undrained soil tests were conducted using a modified triaxial cell and specimens were prepared using the moisture tamping method. Undrained triaxial compression tests were performed at different confining pressures, void ratios and overconsolidation ratios and the samples were sheared to axial strains of about 20% to obtain monotonic loading conditions. It is shown that increasing confining pressures, void ratios and overconsoildation ratios increases the deviator stress, but it has no effect on increasing the dilatant tendencies. It is shown that complete static liquefaction was observed regardless of increases in the confining pressure, void ratio and overconsolidation ratio. Therefore, the confining pressure, void ratio and overconsoildation ratio does not provide significant effects on the liquefaction resistance of the silty sand. The presence of fines in the soil was shown to greatly increase the potential for static liquefaction and creates a particle structure with high compressibility for all cases.

Effects of loading frequency and specimen size on the liquefaction resistance of clean sand

  • Sung-Sik Park;Dong-Eun Lee;Dong-Kiem-Lam Tran
    • Geomechanics and Engineering
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    • v.37 no.2
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    • pp.123-133
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    • 2024
  • This study investigates the effects of loading frequency (f) and specimen size on the liquefaction resistance of clean sand. A series of cyclic direct simple shear tests were conducted on Jumunjin sand with varying consolidated relative densities (40% and 80%), f values (0.05, 0.10, and 0.20 Hz), and diameter to height (D/H) ratios (3.63, 3.18, 2.82, and 2.54). The results demonstrated the significant influence of f and D/H ratio on the number of cycles to liquefaction (Ncyc-liq) and the cyclic resistance ratio (CRR15). It was observed that increasing f linearly increased Ncyc-liq. Increasing the specimen height also led to higher Ncyc-liq values irrespective of the f or relative density. Moreover, a positive correlation between CRR15 and f indicated that higher f yielded higher CRR15. This relationship was more pronounced in dense sand than in loose sand. Specimen height also significantly affected CRR15, with increasing the specimen height resulting in higher CRR15 values. Furthermore, the effect of f on CRR15 was less significant compared to the influence of specimen height. The effect of f on the normalized cyclic resistance ratio (NCRR) was relatively negligible for loose sand but more substantial for dense sand depending on the D/H ratio. Data analysis revealed that the NCRR generally decreases as the D/H ratio increases. An interpolation formula was provided to calculate the NCRR based on the D/H ratio regardless of the f and relative density.

Experimental Study on the Effect of Particle Size Distribution of Soil to the Liquefaction Resistance Strength (입도분포가 액상화 저항강도에 미치는 영향에 관한 실험적 연구)

  • Choi, Mun-Gyu;Seo, Kyung-Bum;Park, Seong-Yong;Kim, Soo-Il
    • Proceedings of the Korean Geotechical Society Conference
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    • 2005.03a
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    • pp.1126-1133
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    • 2005
  • The effects of mean particle size and uniformity coefficient of dredged soils to the liquefaction resistance strength and dynamic characteristics are experimentally studied in this paper. Representative 4 mean particle sizes and 3 uniformity coefficients were selected and 12 representative particle size distribution curves which have different mean particle sizes and uniformity coefficients, were artificially manufactured using the real dredged river soil. Cyclic triaxial tests and torsional shear tests were carried out to analyze the effect of mean particle size and uniformity coefficient to the liquefaction resistance strength and dynamic characteristics of soils.

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Evaluation of Liquefaction Resistance of Sandy Soil Layer in Songlim-park, Pohang, Using Undisturbed Sample (불교란시료를 활용한 포항시 송림공원 사질토층의 액상화저항강도 평가)

  • Kim, Jongkwan;Han, Jin-Tae;Park, Ka-hyun;Lee, Seokhyung
    • Journal of the Korean Geotechnical Society
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    • v.37 no.12
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    • pp.107-116
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    • 2021
  • In this study, a set of laboratory liquefaction test has been conducted using undisturbed samples collected from Songlim-park, Pohang where liquefaction phenomenon had been observed in 2017. Soil samples were frozen right after tube sampling to minimize the disturbances during transport, storage, and test preparation. Cyclic triaxial test has been carried out to evaluate the liquefaction resistance ratio of undisturbed soil samples. As a result, the liquefaction resistance ratio of samples collected from 8.0~8.8 m and 11.0~11.8 m were almost similar, and these values were approximately 0.04~0.07 larger than values estimated by simplified assessment method using field test results. It is expected that the application of undisturbed sample for the evaluation of liquefaction resistance could contribute to the economical design of geotechnical structures.

Comparative Study on the Evaluation of Liquefaction Resistance Ratio According to the Application of the Korean Standard for Cyclic Triaxial Strength Test (반복삼축강도시험의 KS 표준 제정에 따른 액상화 저항강도 평가 비교 연구)

  • Lee, Seokhyung;Han, Jin-Tae;Park, Ka-hyun;Kim, Jongkwan
    • Journal of the Korean Geotechnical Society
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    • v.38 no.9
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    • pp.35-44
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    • 2022
  • The cyclic triaxial strength test is commonly applied as a laboratory test for evaluating the liquefaction resistance ratio. However, the test procedure was not standardized in South Korea until recently; thus, the test results could significantly differ depending on the performer and apparatus, even when identical soil is used. In this study, the American and Japanese standards for the cyclic triaxial strength test were analyzed and the Korean standard was developed considering domestic circumstances. To verify the effectiveness of the standardization of liquefaction laboratory tests, several cases of cyclic triaxial strength tests were conducted and analyzed (1) following the Korean standard and (2) without following any specific instructions for the test procedure. Under (1), the deviation of the liquefaction resistance ratio dramatically decreased.