Evaluation of Excess Pore Water Pressure Build-up During Cyclic Triaxial Tests on a Non-plastic Silt

Abstract

Cyclic loading is responsible for pore water pressure buildup, which may later cause liquefaction and surface settlements. Recent studies emphasize that as the pore water pressure equalizes to initial confining stress, cyclic stress ratio and relative density of soil play a great role in buildup of excess pore water pressure. Nonetheless, pore water pressure is also a function of axial strain. In this regard, cyclic triaxial tests were carried out to evaluate the pore water pressure buildup behavior of a nonplastic silt. It was aimed to determine the dependence of pore water pressure, double amplitude of axial strain and number of cycles on cyclic stress ratio. In this scope,  stress-controlled cyclic triaxial tests at a loading frequency and confining pressure of 0.1 Hz and 100 kPa were carried out on saturated samples. It was understood that number of loading cycles leading to liquefaction were decreased by increases in cyclic stress ratio and relative density. The data obtained in this study, bringing an insight into pore water pressure build-up behavior of nonplastic silts, can be used for practical purposes.  

Keywords

• cyclic triaxial tests
• nonplastic silt
• excess pore water pressure

Plastik olmayan bir silt zemin üzerinde yapılan çevrimsel üç eksenli deneyler sırasında oluşan aşırı boşluk suyu basıncının değerlendirilmesi

Abstract

Çevrimsel yükleme, boşluk suyu basınçlarında artışlar meydana getirerek, daha sonra sıvılaşma ve oturmalara yol açabilmektedir. Yakın zamanda yapılan çalışmalarda, boşluk suyu basıncının ilksel çevre basıncına eşit olması durumunda, çevrimsel gerilme oranı ve zeminin izafi sıkılığının aşırı boşluk suyu basıncının gelişiminde büyük rolü olduğu vurgulanmaktadır. Bununla birlikte, boşluk suyu basıncı aynı zamanda eksenel deformasyonun bir fonksiyonudur. Bu bağlamda, plastik olmayan bir silt zeminin boşluk suyu basıncı gelişim davranışının değerlendirilebilmesi için bir dizi çevrimsel üç eksenli basınç deneyi yapılmıştır. Deneyler ile, boşluk suyu basıncı, çift genlikli eksenel deformayon ve çevrim sayısının çevrimsel gerilme oranına bağımlılığı araştırılmıştır. Bu amaçla, suya doygun örnekler üzerinde gerilme kontrollü çevrimsel üç eksenli basınç deneyleri 0.1 Hz frekansta ve 100 kPa çevre basıncında tatbik edilmiştir. Sıvılaşmaya neden olan çevrim sayısının, artan çevrimsel gerilme oranı ve izafi sıkılık ile azaldığı elde olunmuştur.  Çalışmada elde edilen veriler, plastik olmayan silt zeminin boşluk suyu basıncı gelişim davranışıbı detaylarlandırmaktadır ve pratik amaçlarla kullanılabilir.  

Keywords

• Dinamik üç eksenli deneyler
• plastik olmayan silt
• aşırı boşluk suyu basıncı

References

1. References1 Kramer, S. L. Geotechnical earthquake engineering, Prentice-Hall, Upper Saddle River, NJ, pp 671, 1996.
2. References2 Ishihara, K., Soil behavior in earthquake geotechnics, Clarendon Press, Oxford, pp 360, 1996.
3. References3 Castro, G. and Poulos, S. J., “Factors affecting liquefaction and cyclic mobility” J. Geotech. Eng. Div., 103 (GT6), pp 501-516, 1977.
4. References4 Silver, M. L. and Seed, H. B., “Volume changes in sands during cycling loading” J. Soil Mech. and Foundations Div., ASCE, 9(239), pp 1171-85. 1971.
5. References5 Towhata, I. and Ishihara, K., “Shear work and pore water pressure in undrained shear”, Soils and Foundations, 25(3), pp 73-84, 1985.
6. References6 Matasovic, N., and Vucetic, M., “A pore pressure model for cyclic straining of clay” Soils and Found., 32(3), pp 156–173, 1992.
7. References7 Polito, C. P., Green, R. A., and Lee, J., “Pore pressure generation models for sands and silty soils subjected to cyclic loading” J. Geotech. Geoenviron. Eng., 134(10), pp 1490–1500, 2008.
8. References8 Karim, M. E. and Alam, Md. J., “Effect of non-plastic silt content on the liquefaction behavior of sand-silt mixture” Soil Dynamics and Earthquake Engineering, 65, pp 142-150, 2014.

9. References9 Mortezaie, A. M. and Vucetic, M. M., “Threshold shear strains for cyclic degradation and cyclic pore water pressure generation in two clays” J. Geotech. Geoenviron. Eng., 04(01), 6007, 2016.
10. References10 Liu, J., Guo, T., Zhang, G., Fu, H., “Experimental study on pore pressure generation mode of saturated remolded loess during dynamic liquefaction” 3rd International Conference on Energy Materials and Environment Engineering, IOP Conf. Series: Earth and Environmental Science 61, 012117, 2017.
11. References11 Bol, E., Ozsagir, M., Sert, S., Ozocak, A., “Siltli zeminlerin dinamik özellikleri” 6. Geoteknik Sempozyumu, Adana, Cukurova Universitesi, 2015.
12. References12 Lee K. L., Albaisa, “A Earthquake induced settlements in saturated sands” J Geotech Eng Div. 100 (GT4):387–406, 1974.
13. References13 De Alba, P., Seed, H. B. & Chan, C. K. “Sand liquefaction in large-scale simple shear tests” J. Soil Mech. Found. Div., ASCE 102, No. GT9, pp 909–927, 1976.
14. References14 Dobry, R., Laddi R. S., Chang, R. M., Powell, D. “Prediction of pore water pressure build up and liquefaction of sands during earthquakes by the cyclic strain method” NBS Building Sci. Ser., Wash. DC 138:1–150, 1982.
15. References15 Dobry R. “Liquefaction of soils during earthquakes” National Research Council (NRC), Committee on Earthquake Engineering, Report no. CETS-EE-001, Washington, DC, 1985.
16. References16 Hsu, C.-C. and Vucetic, M., “Volumetric threshold shear strain for cyclic settlement” J. Geotech. Geoenviron. Engng, ASCE 130, No. 1, 58–70, 2004.
17. References17 Erten, D. and Maher, M. H., “Cyclic undrained behavior of silty sand”, Soil Dynamics and Earthquake Engineering,14, pp 115-123, 1995.
18. References18 Singh, S., Liquefaction characteristics of silts” Ground failure under seismic conditions, geotechnical special publication. ASCE 44, pp 105–116, 1994.
19. References19 Sadek, S, Saleh, M., “The effect of carbonaceous fines on the cyclic resistance of poorly graded sands” J. Geotech. Geol. Eng. 25:257–264. doi:10.1007, pp 10706-006-9108-1, 2007.
20. References20 Booker, J. R., Rahman, M. S., and Seed, H. B., GADFLEA—a computer program for the analysis of pore pressure generation and dissipation during cyclic or earthquake loading, EERC Report No. 76-24, Univ. of California, Berkeley, CA, 1976.
21. References21 Chameau, J. L., and Clough, G. W., “Probabilistic pore pressure analysis for seismic loading” J. Geotech. Eng. Div., 109(4), 507–524, 1983.
22. References22 Wang, J., and Kavazanjian, E., “Pore-water pressure development in non-uniform cyclic triaxial tests” John A. Blume Earthquake Engineering Center Rep. No. 73, Technical Dept. of Civil and Environmental Engineering, Stanford Univ., Stanford, CA. 1985.
23. References23 Liyanapathirana, D. S., and Poulos, H., “GA numerical model for dynamic soil liquefaction analysis” Soil Dyn. Earthquake Eng., 22(9–12), pp 1007–1015, 2002.
24. References24 Seed, H. B., Martin, P. P., and Lysmer, J. “The generation and dissipation of pore-water pressures during soil liquefaction” Geotechnical Report No. EERC 75-26, Univ. of California, Berkeley, CA 1975.
25. References25 Marcuson, W. F. Hynes, M. E. and Franklin, A. G., “Evaluation and use of residual strength in seismic safety analysis of embankments”, Earthquake Spectra, 6(3), pp. 529–572. 1990.
26. References26 Oda, M. Kawamoto, K. Suzuki, K. Fujimori, H. and Sato, M., “Microstructural interpretation on reliquefaction of saturated granular soils under cyclic loading”, J. Geotech. Geoenviron. Eng., 127(5), pp. 416–423, 2001.
27. References27 El Hosri, M.S. Biarez, J. and Hicher, P.Y. “Liquefaction characteristics of silty clay”, Proc. 8th World Conf. Earthq. Eng., (3), San Francisco, CA. pp. 277-84. 1984.