Commenced in January 2007
Frequency: Monthly
Edition: International
Paper Count: 30063
Predicting the Effect of Vibro Stone Column Installation on Performance of Reinforced Foundations

Authors: K. Al Ammari, B. G. Clarke

Abstract:

Soil improvement using vibro stone column techniques consists of two main parts: (1) the installed load bearing columns of well-compacted, coarse-grained material and (2) the improvements to the surrounding soil due to vibro compaction. Extensive research work has been carried out over the last 20 years to understand the improvement in the composite foundation performance due to the second part mentioned above. Nevertheless, few of these studies have tried to quantify some of the key design parameters, namely the changes in the stiffness and stress state of the treated soil, or have consider these parameters in the design and calculation process. Consequently, empirical and conservative design methods are still being used by ground improvement companies with a significant variety of results in engineering practice. Two-dimensional finite element study to develop an axisymmetric model of a single stone column reinforced foundation was performed using PLAXIS 2D AE to quantify the effect of the vibro installation of this column in soft saturated clay. Settlement and bearing performance were studied as an essential part of the design and calculation of the stone column foundation. Particular attention was paid to the large deformation in the soft clay around the installed column caused by the lateral expansion. So updated mesh advanced option was taken in the analysis. In this analysis, different degrees of stone column lateral expansions were simulated and numerically analyzed, and then the changes in the stress state, stiffness, settlement performance and bearing capacity were quantified. It was found that application of radial expansion will produce a horizontal stress in the soft clay mass that gradually decrease as the distance from the stone column axis increases. The excess pore pressure due to the undrained conditions starts to dissipate immediately after finishing the column installation, allowing the horizontal stress to relax. Changes in the coefficient of the lateral earth pressure K ٭, which is very important in representing the stress state, and the new stiffness distribution in the reinforced clay mass, were estimated. More encouraging results showed that increasing the expansion during column installation has a noticeable effect on improving the bearing capacity and reducing the settlement of reinforced ground, So, a design method should include this significant effect of the applied lateral displacement during the stone column instillation in simulation and numerical analysis design.

Keywords: Bearing capacity, design, Installation, numerical analysis, settlement, stone column.

Digital Object Identifier (DOI): doi.org/10.5281/zenodo.1339021

Procedia APA BibTeX Chicago EndNote Harvard JSON MLA RIS XML ISO 690 PDF

References:


[1] Allman, M. A. and Atkinson, J. H. (1992). Mechanical properties of reconstituted Bothkennar soil. Géotechnique, Vol. 42, No. 2, 289–301
[2] Ambily, A., Gandhi, S. (2007). Behaviour of Stone Columns Based on Experimental and FEM Analysis. Journal of Geotechnical and Governmental Engineering, ASCE, 133: 405-415.
[3] Brinkgreve, R. B. J and Broere, W. (2011). PLAXIS 3D Foundation Manual Version 2. PLAXIS BV
[4] Castro, J. (2007). Pore pressures during stone column installation. Proc. 18th European Young Geotechnical Engineers' Conference, Ancona
[5] Castro, J. and Sagaseta, C. (2009). Consolidation around stone columns. Influence of column deformation. Int. Journal for Numerical and Analytical Methods in Geomechanics, Vol. 33, Issue 7, 851–877
[6] Debats, J. M., Guetif, Z. and Bouassida, M. (2003). Soft soil improvement due to vibro-compacted columns installation. Proc. Int. Workshop on Geotechnics of Soft Soils - Theory and Practice, Noordwijkerhout, Netherlands, 551–556
[7] Elshazly, H. A., Hafez, D. and Mosaad, M. (2006). Back calculating vibro-installation stresses in stone columns reinforced ground. Proc. of the ICE - Ground Improvement, Vol. 26, Issue 2, 47– 53
[8] Elshazly, H., Elkasabgy, M. and Elleboudy, A. (2008b). Effect of inter-column spacing on soil stresses due to vibro-installed stone columns: Interesting findings. Journal of Geotechnical and Geological Engineering, Vol. 26, No. 2, 225–236
[9] Gäb, M., Schweiger, H. F., Thurner, R. and Adam, D. (2007). Field trial to investigate the performance of floating stone columns. Proc. 14th European Conf. on Soil Mechanics and Geotechnical Engineering, Madrid, 1311–1316
[10] Gäb, M., Schweiger, H. F., Kamrat-Pietraszewska, D. and Karstunen, M. (2008). Numerical analysis of a floating stone column foundation using different constitutive models. Proc. 2nd Int. Workshop on Geotechnics of Soft Soils, Glasgow, 137–142 References 226
[11] Gill, D.R. and Lehane, B.M. (2001). An optical technique for investigating soil displacement patterns. Geotechnical Testing Journal, Vol. 24, 324–329
[12] Guetif, Z. Bouassida, M. Debats, JM. (2007). Improved soft clay characteristics due to stone column installation. Comput Geotech 34: 104-111.
[13] Han, J. and Ye, S. L. (2001). Simplified method for consolidation rate of stone column reinforced foundations. Journal of Geotechnical and Geoenvironmental Engineering, ASCE, Vol. 127, No. 7, 597–603
[14] Hight, D. W., Bond, A. J., and Legge, J. D. (1992). Characterization of the Bothkennar clay: an overview. Géotechnique, Vol. 42, No. 2, 303–347
[15] Jardine, R. J., Lehane, B. M., Smith, P. R. and Gildea, P. A. (1995). Vertical loading experiments on rigid pad foundations at Bothkennar. Géotechnique, Vol. 45, No. 4, 573–597
[16] Keller Foundations Group – Stone Column Installation (Accessed 25 June 2011).
[17] Killeen, M.M., 2012, Numerical modelling of small groups of stone columns (Ph.D. thesis). National University of Ireland, Galway.
[18] Kirsch, F. (2004) vibro stone column installation and its effect on ground improvement. Vortrage der Bavgrundtagung, Leipzin. 149-156 Essen VGE.
[19] Kirsch, F. (2006). Vibro stone column installation and its effect on the ground improvement. Int. Conf. on Numerical Simulation of Construction Processes in Geotechnical Engineering for Urban Environment, Bochum, 115–124
[20] Kirsch, F. (2008). Evaluation of ground improvement by groups of vibro stone columns using field measurements and numerical analysis. Proc. of the 2nd Int. Workshop on the Geotechnics of Soft Soils, Glasgow, 241–248
[21] Leroueil, S., Lerat, P., Hight, D. W. and Powell, J. J. M. (1992). Hydraulic conductivity of a recent estuarine silty clay at Bothkennar. Géotechnique, Vol. 42, No. 2, 275–288
[22] Mitchell, J.K. and Huber, T. R. (1985). Performance of a stone column foundation. Journal Geotechnical Engineering, ASCE, Vol. 11, No. 2, 205–223
[23] Munfakh, G. A., Sarkar, S. K. and Castelli, R. J. (1984). Performance of a test embankment founded on stone columns. Proc. Int. Conf. on Advances in Piling and Ground Testing, London, 259–265
[24] Nash, D. F. T., Sills, G. C. and Davison, L. R. (1992b). One-dimensional consolidation testing of the soft clay from Bothkennar. Géotechnique, Vol. 42, No. 2, 241–256
[25] Plaxis (2008) Plaxis Finite Element Code for Soil and Rock Analyses, 2D-Version AE. Plaxis BV, Delft, The Netherlands.