Journal of the Korean Geosynthetics Society (한국지반신소재학회논문집)

Korean Geosynthetics Society (한국지반신소재학회)
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A Study on the Confined Effects of Highly Moistured Soils Reinforced with Geosynthetics

토목섬유가 보강된 고함수비 흙의 구속효과에 관한 연구

  • Yoo, Jae-Won (Research Institute of Industrial Technology, Pusan National Univ.) ;
  • Im, Jong-Chul (Department of Civil and Environmental Engineering, Pusan National Univ.) ;
  • Kang, Sang-Kyun (Korea Port Engineering Corporation) ;
  • Lee, Hyung-Jun (Department of Civil and Environmental Engineering, Pusan National Univ.) ;
  • Choi, Moon-Bong (Department of Civil and Environmental Engineering, Pusan National Univ.)
  • Received : 2019.01.16
  • Accepted : 2019.03.13
  • Published : 2019.03.30
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Abstract

This study confirms reinforcing effect of geosynthetics in the use of soil at higher water contents as a compaction material on compaction tests, field compaction tests, and numerical analysis. To verify a confined effect, a large mold(area ratio of rammer / mold = 0.19) larger than D compaction mold(area ratio of rammer / mold = 0.33) was performed for compaction. It showed that in the D compaction test, dry density were 0.5~0.6% increases and in the compaction test using the large mold, it were 2.4~3.7% increases at high water contents. It shows that when the area of compacted area is large enough, a confined effect could be arising from the reinforcement of geosynthetics even at high water contents. As a result of analyzing of compaction effects according to 'depth(z/B) from compacted surface' in the field, when not reinforced, the compaction state deteriorated due to the over-compaction and the compaction did not work well. However, when reinforcement of geosynthetics, restraint effect by geosynthetics occurs, it is confirmed that the compaction energy is effectively transferred to the compaction layer and the dry density is increased. Also, through the conceptual model of the behavior of geosynthetic and soil layer, the mechanism in the ground due to reinforcement of geosynthetics is presented and it is verified through finite element analysis.

본 연구에서는 고함수비 상태의 흙의 토목섬유 보강에 의한 다짐효과를 확인하고자 실내다짐실험, 현장다짐실험, 수치해석을 실시하였다. 토목섬유의 구속효과를 검증하기 위해 D다짐실험의 몰드(래머/몰드의 면적비=0.33) 보다 큰 몰드(래머/몰드의 면적비=0.19)를 이용하여 다짐을 실시한 결과, D다짐실험에서는 고함수비 구간의 건조밀도가 0.5~0.6% 증가하였지만, 큰 몰드를 이용한 다짐실험에서는 2.4~3.7%가 증가하는 것으로 분석되어 하중 작용면에 비해 측면지반의 면적이 충분히 넓을 경우, 함수비가 높은 구간에서도 토목섬유 보강에 의한 구속효과가 발생하였다. 현장다짐실험에서 '전압면으로부터의 심도(z/B)'에 따른 고함수비 구간 흙의 다짐효과를 분석한 결과, 무보강 시에는 과도전압으로 인해 다짐상태가 나빠져 다짐이 잘 되지 않았지만, 토목섬유를 보강할 경우 구속효과의 발생으로 다짐층에 다짐에너지가 효과적으로 전달되고 건조밀도가 증가함을 확인하였다. 또한, 토목섬유와 토사층의 거동에 대한 개념적 모델을 통하여 토목섬유의 보강으로 인한 지반내 매커니즘을 설명하였고, 이를 유한요소해석을 통해 검증하였다.

Keywords

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Fig. 1. Particle size distribution curve of ground material used in standard compaction test

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Fig. 2. Type and method of D Proctor compaction test and large mold compaction test

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Fig. 3. Variation of compaction curves obtained by installing geosynthetics (with and without geosynthetics) and by changing compaction type (D and large mold) in compaction tests

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Fig. 4. PET-mat used in field compaction test

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Fig. 5. Specification of compaction equipment

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Fig. 6. Summary of field compaction test sections

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Fig. 7. Determination of number of rolled

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Fig. 8. Dry density by depth of geosynthetics reinforcementof field compaction test

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Fig. 9. Conceptual drawing of reinforcement mechanism describing effect of geosynthetics on dry density of soil layers under compaction force (Kim et al., 2018)

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Fig. 10. Process of finite element method

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Fig. 11. Results of horizontal and vertical displacements with and without reinforcement by finite element method

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Fig. 12. Results of horizontal and vertical displacement behavior according to the number of reinforcement layers of geosynthetics

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Fig. 13. Results of horizontal and vertical displacement behavior according to reinforcement position of geosynthetics

Table 1. Physical properties of soil (KS F 2324, 2016)

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Table 2. Physical properties of PET-mat

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Table 3. The type and conditions of D Proctor compaction test and large mold compaction test

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Table 4. Results of compaction energy of D Proctor compaction test and large mold compaction test

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Table 5. Results of D Proctor compaction test and large mold compaction test

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Table 6. The results of D Proctor compaction test with geosynthetics

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Table 7. The results of Proctor test compaction tests using geosynthetics at high water contents

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Table 8. Distribution of natural ground (field compaction test)

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Table 9. Condition and type of field compaction tests according to reinforcement of geosynthetics

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Table 10. Condition and type of field compaction test according to reinforcement of PET-mat

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Table 11. Condition and type of field compaction test according to reinforcement of PET-mat

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Table 12. Soil applied the finite element analysis method (Mohr-Coulomb model)

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