Bearing Capacity of Spread Footings on Aggregate Pier Reinforced Clay
Publication: Journal of Geotechnical and Geoenvironmental Engineering
Volume 139, Issue 1
Abstract
Aggregate piers, also known as stone columns, are a commonly used ground improvement technique to stiffen existing soils for the support of structure foundations. This paper presents an evaluation of existing analytical expressions for the bearing capacity of spread footings supported on aggregate pier reinforced clay. The accuracy of these models was investigated using a database of high-quality footing load test data. The existing models were compared using the bias (i.e., the ratio of measured and calculated bearing capacity), and they produced a wide range in predicted bearing capacities. Selected analytical models were empirically modified using the load test database, and this resulted in improved accuracy and reduced variability. Back-calculated aggregate pier bearing capacity and cavity expansion factors are shown to be inversely proportional to undrained shear strength, and therefore to the ultimate confining pressure available at failure. This finding is attributed to the curved failure envelope of the angular aggregate used in pier construction. Additionally, a multiple nonlinear regression model suitable for spread footings resting on aggregate piers under a wide range of pier configurations is presented. The regression model is shown to produce more accurate bearing capacity estimates than existing analytical models.
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Acknowledgments
The authors thank Hayward Baker, Inc., for constructing the test aggregate piers and for funding the test program. Additional support provided by the Valle and ARCS Fellowship Programs of the University of Washington is gratefully acknowledged.
Disclaimer
None of the aggregate piers tested as part of this study were designed, installed, or tested by, under the supervision, with authorization from, or in compliance with the specifications for the patented and proprietary technology of Geopier. The installation and testing was not conducted by any independent party.
References
Aboshi, H., Ichimoto, E., Enoki, M., and Harada, K. (1979). “The composer—A method to improve characteristics of soft clays by inclusion of large diameter sand columns.” Proc., Reinforced Earth and Other Techniques, Vol. 1, Int. College on Soil Reinforcement, Paris.
Barksdale, R. D., and Bachus, R. C. (1983). “Design and construction of stone columns.” Rep. No. FHWA/RD 83/026, Federal Highway Administration, Washington, DC.
Baumann, V., and Bauer, G. E. A. (1974). “The performance of foundation on various soils stabilized by vibrocompaction method.” Can. Geotech. J., 11(4), 509–530.
Bell, A. L. (1915). “The lateral pressure and resistance of clay and the supporting power of clay foundations.” Proc., Inst. Civ. Eng., Institution of Civil Engineers, London, 223–272.
Bergado, D. T., Huat, S. H., and Kalvade, S. (1987). “Improvement of soft Bangkok clay using granular piles in subsiding environment.” Proc., 5th Int. Geotechnical Seminar on Case Histories in Soft Clay, Nanyang Technological Institute, Singapore, 219–226.
Bergado, D. T., and Lam, F. L. (1987). “Full scale load test of granular piles with different densities and different proportions of gravel and sand in the soft Bangkok clay.” Soils Found., 27(1), 86–93.
Brauns, J. (1978). “Initial bearing capacity of stone columns and sand piles.” Vol. I, Proc., Soil Reinforcing and Stabilizing Techniques in Engineering Practice, New South Wales Institute of Technology, Sydney, Australia, 497–512.
Cadden, A., Gomez, J., Bruce, D., and Armour, T. (2004). “Micropiles: Recent advances and future trends.” Current practices and future trends, GSP No. 125, ASCE, Reston, VA.
Chin, F. K. (1970). “Estimation of the ultimate load of piles not carried to failure.” Proc., 2nd Southeast Asian Conf. on Soil Engineering, Southeast Asian Geotechnical Society, Thailand, 81–90.
Duncan, J. M., Brandon, T., Jian, W., Park, Y., Griffith, T., Corton, J., and Ryan, E. (2007). “Densities and friction angles of granular materials with standard gradations 21b and #57.” Rep. CPGR #45, Center for Geotechnical Practice and Research, Virginia Polytechnic Institute, Blacksburg, VA.
Engelhardt, K., and Golding, H. C. (1975). “Field testing to evaluate stone column performance in a seismic area.” Geotechnique, 25(1), 61–69.
Gibson, R. E., and Anderson, W. F. (1961). “In situ measurement of soil properties with the pressuremeter.” Civ. Eng. Public Works Rev., 56(658), 615–618.
Greenwood, D. A. (1970). “Mechanical improvement of soils below ground surface.” Proc., Conf. on Ground Engineering, Institution of Civil Engineers, London.
Greenwood, D. A. (1975). “Vibroflotation: Rationale for design and practice.” Methods of treatment of unstable ground, F. G. Bell, ed., Newness-Buttersworth, London, 189–209.
Han, J., and Ye, S. (1991). “Field tests of soft clay stabilized by stone columns in coastal areas of China.” Proc., 4th Int. Deep Foundations Institute Conf., Vol. 1, Balkema, Rotterdam, Netherlands.
Hansen, J. B. (1963). “Discussion of ‘Hyperbolic stress-strain response: Cohesive soils’ by R. L. Kondner.” J. Soil Mech. and Found. Div., 89(4), 241–242.
Hughes, J. M. O., and Withers, N. J. (1974). “Reinforcing of soft cohesive soils with stone columns.” Ground Eng., 7(3), 42–49.
Hughes, J. M. O., Withers, N. J., and Greenwood, D. A. (1975). “A field trial of the reinforcing effect of a stone column in soil.” Geotechnique, 25(1), 31–44.
Jeon, S. S., and Kulhawy, F. H. (2001). “Evaluation of axial compression behavior of micropiles.” Foundations and Ground Improvement, GSP No. 113, T. L. Brandon, ed., ASCE, Reston, VA, 460–471.
Lacasse, S., and Nadim, F. (1996). “Uncertainties in characterising soil properties.” Uncertainty in the geologic environment: From theory to practice, GSP No. 58, ASCE, Reston, VA, 49–75.
Lawton, E. C., and Warner, B. J. (2004). “Performance of a group of Geopier elements loaded in compression compared to single Geopier elements and unreinforced soil.” Rep. No. UUCVEEN 04-12, Univ. of Utah, Salt Lake City, 257.
Lillis, C., Lutenegger, A. J., and Adams, M. (2004). “Compression and uplift of rammed aggregate piers in clay.” GeoSupport 2004, GSP No. 124, J. P. Turner and P. W. Mayne, eds., ASCE, Reston, VA.
Madhav, M. R., Iyenger, N. G. R., Vitkar, R. P., and Nandia, A. (1979). “Increased bearing capacity and reduced settlements due to inclusions in soil.” Proc., Int. Conf. on Soil Reinforcement: Reinforced Earth and Other Technologies, Vol. 2, Association Amicale des Ingenieurs, Paris.
Madhav, M. R., and Vitkar, R. P. (1978). “Strip footing on weak clay stabilized with a granular trench or pile.” Can. Geotech. J., 15(4), 605–609.
Meyerhof, G. G. (1965). “Shallow foundations.” J. Soil Mech. and Foundation Div., 91(2), 21–31.
Mitchell, J. K. (1981). “Soil improvement—State-of-the-art report.” Proc., 10th Int. Conf. on Soil Mechanics and Foundation Engineering, Session 12, Int. Society of Soil Mechanics and Foundation Engineering, London, Vol. 4, 506–565.
Montgomery, D. C., and Runger, G. C. (2010). Applied statistics and probability for engineers, 5th Ed., Wiley, New York, 768.
Stuedlein, A. W. (2008). “Bearing capacity and displacement of spread footings on aggregate pier reinforced clay.” Ph.D. thesis, Univ. of Washington, Seattle.
Stuedlein, A. W., and Holtz, R. D. (2010). “Undrained displacement behavior of spread footings in clay.” The art of foundation engineering practice, honoring Clyde N. Baker, Jr., P.E., S.E., GSP 198, ASCE, Reston, VA, 653–669.
Stuedlein, A. W. and Holtz, R. D. (2012). “Analysis of footing load tests of aggregate piers in clay.” J. Geotech. Geoenviron. Eng., 138(9), 1091–1103.
Stuedlein, A. W., Kramer, S. L., Arduino, P., and Holtz, R. D. (2012a). “Geotechnical characterization and random field modeling of desiccated clay.” J. Geotech. Geoenviron. Eng., 138(11), 1301–1313.
Stuedlein, A. W., Kramer, S. L., Arduino, P., and Holtz, R. D. (2012b). “Reliability of spread footing performance in desiccated clay.” J. Geotech. Geoenviron. Eng., 138(11), 1314–1325.
Van Impe, W. F., De Cock, F., Van Der Cruyssen, J. P., and Maertens, J. (1997). “Soil improvement experiences in Belgium: Part II. Vibrocompaction and stone columns.” Ground improvement, Vol. 1, Thomas Telford, London.
Vesic, A. S. (1972). “Expansion of cavities in infinite soil mass.” J. Soil Mech. and Found. Div., 98(3), 265–290.
White, D. J., Pham, H. T., and Hoevelkamp, K. K. (2007). “Support Mechanisms of rammed aggregate piers. I: Experimental results.” J. Geotech. Geoenviron. Eng., 133(12), 1503–1511.
Information & Authors
Information
Published In
Journal of Geotechnical and Geoenvironmental Engineering
Volume 139 • Issue 1 • January 2013
Pages: 49 - 58
Copyright
© 2013 American Society of Civil Engineers.
History
Received: Dec 5, 2011
Accepted: Apr 16, 2012
Published online: Apr 18, 2012
Published in print: Jan 1, 2013
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