Journal of the Society of Disaster Information (한국재난정보학회 논문집)

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Analysis of Isochrone Effect of Clayey Soils using Numerical Analysis

수치해석을 이용한 점성토 지반의 아이소크론 영향 분석

  • Lee, Yun-Sic (Jeongmin Geo Tech) ;
  • Lee, Jong-Ho (Department of Civil and Environmental Engineering, Daejin University) ;
  • Lee, Kang-Il (Department of Civil Engineering, Daejin University)
  • Received : 2018.12.29
  • Accepted : 2019.02.27
  • Published : 2019.03.29
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Abstract

Purpose: The consolidation settlement of soft ground is dependent on the distribution of pore water pressure which is also affected by hydraulic conductivities (boundary condition) of layers, thickness of clayey soil layer and surcharge. Results: However, the current consolidation analyses are mostly based on Terzaghi's consolidation theory that assumes the initial pore water pressure ratio with depth to be constant. In this study, numerical analysis are carried out to investigate the variation of pore water pressure dissipation with depth and thickness of clayey soil layer, time, surcharge as well as drainage conditions. Conclusion: Comparative study with Terzaghi's consolidation theory is also conducted. The result shows that Terzaghi's consolidation theory should be used with caution unless it is ideally corresponded to the isochrone.

연구목적 : 연약지반의 압밀침하는 연약 점토층 상하부에 분포하는 지층의 투수성(경계조건), 점토층의 두께, 그리고 하중 재하 폭에 따라 간극수압 분포특성이 달라짐에도 불구하고, 현재 설계의 대부분은 점토층의 깊이에 따른 초기간극비가 일정하다는 가정 하에 제안된 Terzaghi 1차원 압밀이론에 의한 아이소크론(Isochrone)을 이용하여 압밀시간을 산정하고 있다. 연구방법 : 따라서 본 연구에서는 하중 재하 폭, 점토층의 두께, 그리고 점토층 하부의 배수조건이 변화할 때 발생하는 과잉간극수압 소산형태를 수치해석적 방법으로 점토의 깊이별로 시간에 따른 과잉간극수압 변화를 체크하고, 이를 Terzaghi 1차원 압밀이론에 의한 아이소크론과 비교 분석하여 합리적인 압밀시간 결정방법을 제시하고자 한다. 연구결과 : 본 연구 결과, Terzaghi가 제안한 압밀도-시간계수 곡선에 가장 이상적인 경우가 아닌 경우에는 Terzaghi 1차원 압밀이론에 의한 압밀도-시간계수 곡선, 압밀시간 산정에 유의해야 하며, 가능한 수치해석에 의한 압밀도-시간계수 곡선을 사용하여 압밀시간을 산정하여야 한다.

Keywords

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Fig. 1. Terzaghi 1-D Consolidation theory of isochrone (Terzaghi, 1943)

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Fig. 2. Average degree of consolidation-time factor(Terzaghi, 1943)

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Fig. 3. Isochrone form according to boundary conditions (Terzaghi, 1943)

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Fig. 4. Pore water pressure measurement point according to depth

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Fig. 6. Degree of consolidation-time factor according to thickness of clay layer(Permeable layer condition)

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Fig. 7. Comparison of isochrone type according to thickness of clay layer (Impervious layer condition)

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Fig. 8. Degree of consolidation-time factor according to thickness of clay layer(Impervious layer condition)

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Fig. 9. Comparison of isochrone type according to loading width (Permeable layer condition)

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Fig. 10. Degree of consolidation-time factor according to loading width(Permeable layer condition)

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Fig. 11. Comparison of isochrone type according to loading width (Impervious layer condition)

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Fig. 12. Degree of consolidation-time factor according to loading width(Impervious layer condition)

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Fig. 5. Comparison of isochrone type according to thickness of clay layer(Permeable layer condition)

Table 1. Average degree of consolidation-time factor

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Table 2. Numerical analysis and isochrone correlation

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Table 3. Isochrone analysis method using numerical analysis

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Table 4. Numerical analysis condition

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Table 5. Consolidation characteristics of clay layer

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Table 6. Average degree of consolidation of Terzaghi, CASE A and B

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Table 7. Average degree of consolidation of CASE A and B

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Table 8. Average degree of consolidation of Terzaghi, CASE D and E

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Table 9. Average degree of consolidation of CASE D and E

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Table 10. Average degree of consolidation of Terzaghi, CASE B and C

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Table 11. Average degree of consolidation of CASE A and C

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Table 12. Average degree of consolidation of Terzaghi, CASE E and F

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Table 13. Average degree of consolidation of CASE E and F

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References

  1. Abbasi, N., Rahimi, H., Javadi, A.A. and Fakher, A. (2007). "Finite difference approach for consolidation with variable compressibility and permeability." Computers and Geotechnics, Vol. 34, No. 1, pp.41-52. https://doi.org/10.1016/j.compgeo.2006.09.003
  2. Davis, E.H., Raymond, G.P. (1965). "A Non-linear theory of consolidation." Geotechnique, Vol. 15, No. 2, pp.161-173. https://doi.org/10.1680/geot.1965.15.2.161
  3. Gibson, R.E., Schiffman, R.L., Cargill, K.W. (1981). "The theory of one-dimensional consolidation of saturated clays: II. Finite nonlinear consolidation of thick homogeneous layers." Canadian Geotechnical Journal, Vol. 18, No. 2, pp. 280-293. https://doi.org/10.1139/t81-030
  4. Lee, K., Sills G. C. (1981). "The consolidation of a soil stratum, including self-weight effects and large strains." International journal for numerical and analytical methods in geomechanics, Vol. 5, pp. 405-428. https://doi.org/10.1002/nag.1610050406
  5. Lee, S., Bae, Y.-H., Yang, T.-S., Hwang, K.-H. (1993). "A Study on the Characteristics of Self-weight Consolidation in Dredged and Reclaimed Clays." Journal of the University Seoul, Vol. 27, pp. 173-191.
  6. Lekha, K.R., Krishnaswamy, N.R., Basak, P. (2003). "Consolidation of clays for variable permeability and compressibility." J. Geotech. and Geoenvir. Engrg., Vol. 129, No. 11, pp. 1001-1009. https://doi.org/10.1061/(ASCE)1090-0241(2003)129:11(1001)
  7. Richart, F.E. (1957). "Review of the theories for sand drains." Transactions of ASCE, Vol. 124, No. 2999, pp.709-736.
  8. Terzaghi, K. (1943). Theoretical Soil Mechanics. Wiley, New York.
  9. Vaid, Y. P. (1985). "Constant rate of loading nonlinear consolidation." Soils and Foundation, Vol. 25, No. 1, pp. 105-108. https://doi.org/10.3208/sandf1972.25.105
  10. Xie, K.H., Leo, C.J. (2004). "Analytical solutions of one-dimensional large strain consolidation of saturated and homogeneous clays." Computers and Geotechnics, Vol. 31, pp. 301-314. https://doi.org/10.1016/j.compgeo.2004.02.006
  11. Xie, K.H., Xie, X.Y., Jiang, W. (2002). "A study on one-dimensional nonlinear consolidation of doublelayered soil." Computers and Geotechnics, Vol. 29, pp. 151-168. https://doi.org/10.1016/S0266-352X(01)00017-9
  12. Yoo, N.-J., Lee, M.-W., Lee, J.-H. (1995). "Estimation of Consolidation Settlement of Soft Clay due to Selfweight by the Finite Strain Consolidation Theory." Journal of the Korean Society of Civil Engineers, Vol.15, No.5, pp.1417-1427.