Numerical Investigation of Soft Clayey Soil Improved by Soil-Cement Columns under Harmonic Load

Authors: R. Ziaie Moayed, E. Ghanbari Alamouty

Abstract:

Deep soil mixing is one of the improvement methods in geotechnical engineering which is widely used in soft soils. This article investigates the consolidation behavior of a soft clay soil which is improved by soil-cement column (SCC) by numerical modeling using Plaxis2D program. This behavior is simulated under vertical static and cyclic load which is applied on the soil surface. The static load problem is the simulation of a physical model test in an axisymmetric condition which uses a single SCC in the model center. The results of numerical modeling consist of settlement of soft soil composite, stress on soft soil and column, and excessive pore water pressure in the soil show a good correspondence with the test results. The response of soft soil composite to the cyclic load in vertical direction also compared with the static results. Also the effects of two variables namely the cement content used in a SCC and the area ratio (the ratio of the diameter of SCC to the diameter of composite soil model, a) is investigated. The results show that the stress on the column with the higher value of a, is lesser compared with the stress on other columns. Different rate of consolidation and excessive pore pressure distribution is observed in cyclic load problem. Also comparing the results of settlement of soil shows higher compressibility in the cyclic load problem.

Keywords: Area ratio, consolidation behavior, cyclic load, numerical modeling, soil-cement column.

Digital Object Identifier (DOI): doi.org/10.5281/zenodo.2363207

References:

[1] R. Babasaki, K. Suzuki, S. Saitoh, Y. Suzuki K. and Tokitoh, “Construction and testing of deep foundation improvement using the deep cement mixing method,” Deep Foundation Improvements: Design, Construction and Testing, ASTM STP 1089, M. I. Esrig and R. C. Bachus, eds. ASTM, Philadelphia, pp 224–233, 1991.
[2] D. A. Bruce, M. E. C. Bruce and A. F. DiMillio, “Deep mixing method: A global perspective,” Geotechnical Special Publication no. 81. Soil Improvement for Big Digs, Proc. Sessions of Geo-Congress, Boston, pp 1–26, 1998.
[3] A. Porbaha, “State of art in deep mixing technology. part 1: basic concepts and overview,” Ground Improvement, vol. 2, no 2, pp 81-92, 1998.
[4] A. Porbaha, H. Tanaka, and M. Kobayashi, “State of art in deep mixing technology. part 2: applications,” Ground Improvement, vol. 2, no 3, pp 125–139, 1998.
[5] Y. Shao, J. M. Emir and C. Weiming, “Compound deep soil mixing columns for retaining structures in excavations,” Journal of Geotechnical and Geoenvironmental Engineering, vol. 131 (November), pp 1370–77, 2005.
[6] F. H. Lee, Y. Lee, S.-H. Chew, and K. Y. Yong, “Strength and modulus of marine clay-cement mixes,” Journal of Geotechnical and Geoenvironmental Engineering, vol. 131, no. 2, pp 178–186, 2005.
[7] F. H. Lee, C. H. Lee, and G. R. Dasari, “Centrifuge modelling of wet deep mixing processes in soft clays,” Geotechnique, vol. 56, no. 10, pp 677-691, 2006.
[8] S. L. Shen, J. Han, and Y. J. Du, “Deep mixing induced property changes in surrounding sensitive marine clays,” Journal of Geotechnical and Geoenvironmental Engineering, vol. 134, no. 6, pp 845-854, 2008.
[9] A. Sukpunya, and A. Jotisankasa, “Large simple shear testing of soft Bangkok clay stabilized with soil–cement-columns and its application,” Soils and Foundations, vol. 56, no 4, pp 640-651, 2016.
[10] P. J. Venda Oliveira, J. L. P. Pinheiro, A. A. S. Correia, “Numerical analysis of an embankment built on soft soil reinforced with deep mixing columns: parametric study,” Computers and Geotechnics, vol. 38, no. 4, pp 566-576, 2011.
[11] P. Voottipruex, T. Suksawat, D. T. Bergado, and P. Jamsawang, “Numerical simulations and parametric study of SDCM and DCM piles under full scale axial and lateral loads,” Computers and Geotechnics, vol. 38, no. 3, pp 318-329, 2011.
[12] S. Horpibulsuk, A. Chinkulkijniwat, A. Cholphatsorn, J. Suebsuk, and M. D. Liu, “Consolidation behavior of soil-cement column improved ground,” Computers and Geotechnics, vol. 43, pp 37-50, 2012.
[13] R. Ignat, S. Baker, S. Larsson, and S. Liedberg, “Two and three-dimensional analyses of excavation support with rows of dry deep mixing columns,” Computers and Geotechnics, vol. 66, pp. 16-30, 2015.
[14] R. W. Clough, and J. Penzien, Dynamics of structures. Second Edition, McGraw-Hill, New York, 1993.