• Title/Summary/Keyword: Subgrade soils

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Correlation Analysis Between Geotechnical Properties and CBR Values of Subgrade Materials in Rural Road Construction (농촌도로 노상토 재료의 공학적 특성과 CBR값의 관계 분석)

  • 송태균;권무남
    • Magazine of the Korean Society of Agricultural Engineers
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    • v.38 no.4
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    • pp.89-98
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    • 1996

  • This study was conducted to evaluate the relationships between the geotechnical properties and the CBR values of the subgrade materials used in the rural roal construction. A total of 77 Soil samples was investigated and tested from 45 agricultural and industrial sites in Kyungpook Province. The results obtained are as follows : 1. The maximum dry densities of the coarse grained soils are larger than those of the fine grained soils. The optimum moisture contents of the coarse grained soils are smaller than those of the fine grained scils. 2. The mean values of the medified CBR values of the soils classified by the USCS, are decreased in the order of GP-GM, SW-SM, GM, SC, SP-SM, ML, CL-ML. And, those classified by the AASHTO are decreased in the order of A-i-a, A-i-b, A-2-4, A-3, A-4, A-6, A-7-6. 3. As passing percentage of No.200 sieve is increased, the CBR Value of soils is decreased gradually. 4. As the optimum moisture contents of the soil is increased, the CBR values is decresed the maximum dry density of the soils increased, the CBR values increased. 5. The CBR values are decreased as Group-lndex(GI) are increased. And Activity(A) is showed no relation with the CBR values. 6. The relation ships between the modified CBR value and standand proctor compaction CBR value at 95% compaction ratio can he expressed as the following equation : Y(CERmod)= 2.3638 + 0.8922X(CBR25).

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Evaluation of Field Nonlinear Modulus of Subgrnde Soils Using Repetitive Static Plate Bearing Load Test (반복식 평판재하시험을 이용한 노상토의 현장 변형계수 평가)

  • Kim Dong-Soo;Seo Won-Seok;Kweon Gi-Chul
    • Journal of the Korean Geotechnical Society
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    • v.21 no.6
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    • pp.67-79
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    • 2005

  • The field plate load test has a good potential for determining modulus since it measures both plate pressure and settlement. Conventionally the modulus has been assumed to be a constant secant value defined from the settlement of the plate at a given load intensity. A constant modulus (modulus of subgrade reaction, k), however, may not be a representative value of subgrade soil under working load. Field strain(o. stress)-dependent modulus characteristics of subgrade soils, at relatively low to intermediate strains, are important in the pavement design. In this study, the field strain dependent moduli of subgrade soils were obtained using cyclic plate load test. Testing procedure and data reduction method are proposed. The field crosshole and laboratory resonant column tests were also performed to determine field nonlinear modulus at $0.001\%\;to\;0.1\%$ strains, and the modulus values and nonlinear trends are compared to those obtained by cyclic plate load tests. Both modulus values match relatively well when the different state of stress between two tests was considered, and the applicability of field cyclic plate load test for determining nonlinear modulus values of subgrade soils is verified.

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Mechanical properties and failure mechanism of gravelly soils in large scale direct shear test using DEM

  • Tu, Yiliang;Wang, Xingchi;Lan, Yuzhou;Wang, Junbao;Liao, Qian
    • Geomechanics and Engineering
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    • v.30 no.1
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    • pp.27-44
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    • 2022

  • Gravelly soil is a kind of special geotechnical material, which is widely used in the subgrade engineering of railway, highway and airport. Its mechanical properties are very complex, and will greatly influence the stability of subgrade engineering. To investigate the mechanical properties and failure mechanism of gravelly soils, this paper introduced and verified a new discrete element method (DEM) of gravelly soils in large scale direct shear test, which considers the actual shape and broken characteristics of gravels. Then, the stress and strain characteristics, particle interaction, particle contact force, crack development and energy conversion in gravelly soils during the shear process were analyzed using this method. Moreover, the effects of gravel content (GC) on the mechanical properties and failure characteristics were discussed. The results reveal that as GC increases, the shear stress becomes more fluctuating, the peak shear stress increases, the volumetric strain tends to dilate, the average particle contact force increases, the cumulative number of cracks increases, and the shear failure plane becomes coarser. Higher GC will change the friction angle with a trend of "stability", "increase", and "stability". Differently, it affects the cohesion with a law of "increase", "stability" and "increase".

  • https://doi.org/10.12989/gae.2022.30.1.027 인용 KSCI