The Small Strain Effects to the Shear Strength and Maximum Stiffness of Post-Cyclic Degradation of Hemic Peat Soil

Authors: Z. Adnan, M. M. Habib

Abstract:

The laboratory tests for measuring the effects of small strain to the shear strength and maximum stiffness development of post-cyclic degradation of hemic peat are reviewed in this paper. A series of laboratory testing has been conducted to fulfil the objective of this research to study the post-cyclic behaviour of peat soil and focuses on the small strain characteristics. For this purpose, a number of strain-controlled static, cyclic and post-cyclic triaxial tests were carried out in undrained condition on hemic peat soil. The shear strength and maximum stiffness of hemic peat are evaluated immediately after post-cyclic monotonic testing. There are two soil samples taken from West Johor and East Malaysia peat soil. Based on these laboratories and field testing data, it was found that the shear strength and maximum stiffness of peat soil decreased in post-cyclic monotonic loading than its initial shear strength and stiffness. In particular, degradation in shear strength and stiffness is more sensitive for peat soil due to fragile and uniform fibre structures. Shear strength of peat soil, τ_max = 12.53 kPa (Beaufort peat, BFpt) and 36.61 kPa (Parit Nipah peat, PNpt) decreased than its initial 58.46 kPa and 91.67 kPa. The maximum stiffness, G_max = 0.23 and 0.25 decreased markedly with post-cyclic, G_max = 0.04 and 0.09. Simple correlations between the G_max and the τ_max effects due to small strain, ε = 0.1, the G_max values for post-cyclic are relatively low compared to its initial G_max. As a consequence, the reported values and patterns of both the West Johor and East Malaysia peat soil are generally the same.

Keywords: Post-cyclic, strain, shear strength, maximum stiffness.

Digital Object Identifier (DOI): doi.org/10.5281/zenodo.1132018

References:

[1] B. Simpson, O'Riordan, N. J., Croft, D. D., 1979. A computer model for the analysis of ground movements in London Clay. Géotechnique 29 (2), 149–175.
[2] S. N. Likitlersuanga, S. Teachavorasinskuna, C. C. Surarakb, E. Ohc, and A. Balasubramaniam. 2013. Small strain stiffness and stiffness degradation curve of Bangkok Clays. The Japanese Geotechnical Society. Production and hosting by Elsevier B.V.
[3] Atkinson, J. H., Sallfors, G., 1991. Experimental determination of soil properties. In: Proceedings of the 10th ECSMFE, vol. 3, Florence, pp. 915–956.
[4] S. N. A. Zolkefle. 2014. “The Dynamic Properties of Peat Soil in South West of Johor”. A Master Degree Thesis. Universiti Tun Hussein Onn Malaysia.
[5] M. M Habib, Z. Adnan. 2015. Pre- and Post-Cyclic Behavior on Monotonic Shear Strength of Penor Peat. Electronic Journal of Geotechnical Engineering. Vol. 20 (2015), Bund. 15, 6928.
[6] B. W Song. 2002. The Influence of initial static shear stress on Post Cyclic degradation of non-plastic silt. Lowland technology International. Vol. 4, No. 2, 14 – 24 December 2002, ISSN 1344 – 9656.
[7] Vucetic, M., Lanzo, G., and Doroudian, M. (1998): Damping at Small Strains in Cyclic Simple Shear Test, ASCE Journal of Geotechnical and Geoenvironmental Engineering, Vol. 124, No.7, pp.585-594.
[8] M. M. Habib. 2015. “Post-cyclic Behaviour of Malaysian Peat Soil”. A Master Degree Thesis. Universiti Tun Hussein Onn Malaysia.
[9] Y. Duraisamy and B. K. H. Bujang. (2008). Method of Utilizing Cheap Land for Infrastructure Development, Methods of utilizing cheap land for infrastructure development ICCBT.
[10] S. Kazemian, B. B. K. Huat and A. Prasad. 2011. Study of Peat Media on Stabilization of Peat by Traditional Binders, Int. J. Phys. Sci., 6(3): 476-481.
[11] B. K. Huat. 2004. Organic and Peat Soils Engineering. Serdang: University Putra Malaysia Press.
[12] M. Vucetic. (1994). Cyclic threshold shear strains in soils, J. Geotechnical Engineering, 120 (12), 2208-2228.
[13] BS 1377-8:1990. Methods of test for soils for civil engineering purposes. Shear strength tests (effective stress).
[14] T. Kishida, R. W. Boulanger, T. M. Wehling and M. W. Driller. 2006. Variation of Small Strain Stiffness for Peat and Organic Soil.
[15] K. H. Sloekoe and W. R. Hudson. 1992. Deformational Characteristics of soils at Small to Intermediate Strains from Cyclic Tests. Center for Transportation Research, the University of Texas at Austin, Austin, Texas.
[16] R. Dobry and M. Vucetic. 1987. Dynamic Properties and Seismic Response of Soft Clay Deposits, Proceedings, International Symposium on Geotechnical Engineering of Soft Soils, Vol 2, Mexico City, pp 51-87.
[17] K. Ishihara (1996). Soil Behaviour in Earthquake Geotechnics, Oxford, Clarendon Press