The main objective of this study is to understand the performance of grout pile– reinforced soft clay using a revised CBR test setup. In this study, two types of revised CBR tests were designed. Two mold setups, namely single mold and double mold, per specimen (unreinforced and grout – pile reinforced soft clay) were prepared for the first type of revised CBR test. Using the stress –settlement curves obtained from the first type of revised CBR test, the effect of pile length on load bearing capacity was investigated and value of the stress concentration ratio were determined. Furthermore, the potential of the revised CBR test in predicting the modulus of subgrade reaction was also assessed. In addition, another set of specimens of grout pile – reinforced soft clay using the double mold setup was prepared for the second type of revised CBR test in order to determine the load carried by the grout pile alone at various settlements. The load carried by the grout pile alone with varying lengths at a specified settlement together with the load carried by the unreinforced soft clay at the same settlement were used to estimate the equivalent composite strength of grout pile – reinforced soft clay. Based on the results, the effect of pile on load bearing capacity the double mold setup was able to capture the performance of grout pile – reinforced soft clay. The maximum reduction in settlement using the double mold setups for a grout pile-reinforced soft clay with 90 mm length was 27%. The value of the stress concentration ratio, n, increases with increasing pile length and imposed load bearing capacity. The total improvement in the modulus of subgrade reaction for the grout pile-reinforced soft clay with 90 mm has reach 28%. The combined load capacities of unreinforced soft clay and grout pile alone overestimates the measured load capacity of grout pile – reinforced soft clay (composite system).

Avci, B., & Gurbuz, A. (2018). Modulus of subgrade reaction that varies with magnitude of displacement of cohesionless soil. Arabian Journal of Geosciences, 11(13), 1–8. https://doi.org/10.1007/s12517-018-3713-1
Bowles, J. E. (1996). Foundation Analysis and Design. McGraw-Hill International Book Company. https://doi.org/10.1007/978-1-349-13729-9_26
Das, B. M. (2006). Principles of Geotechnical Engineering. Chris Carson
Das, B. M. (1997). Principles of Foundation Enginerring (4th ed.).Boston, MA: PWS Publishing Co.
Han, J. (2015). Principles and practice of ground improvement. John Wiley and Sons.
Heukelom, W., & Klomp, A. J. G. (1962). Dynamic testing as a means of controlling pavements during and after construction. In A. Arbor (Ed.), Proceedings International Conference on the Structural Design of Asphalt Pavement (pp. 667–679).
Hewlett, W. J., & Randolph, M. F. (1988). Analysis of piled embankments. Ground Engineering, 21(3), 12–18.
Jones, G. (1997). Analysis of Beams on Elastic Foundations using Finite Difference Theory. Thomas Telford.
Kameswara Rao, N. S. V. (2000). Dynamic soil tests and applications (First Edit). A. H. Wheeler & Co. Ltd.
Kitazume, M., & Terashi, M. (2013). The Deep Mixing Method (1st ed.). London, UK:CRC Press
Low, B. K., Tang, S. K., & Choa, V. (1994). Arching in piled embankment. Journal of Geotechnical Engineering, 120(11), 1917–1938.
MnDoT. (2007). Pavement Manual (Chapter 3). Minnesota Department of Transport.
Moayed, R. Z., & Janbaz, M. (2009). Effective parameters on modulus of subgrade reaction in clayey soils. Journal of Applied Science, 9, 4006–4012.
Naeini, S. A., Ziaie Moayed, R., & Allahyari, F. (2014). Subgrade Reaction Modulus (Ks) of Clayey Soils Based on Field Tests. Joournal of Engineering Geology, 8(1), 2021–2046.
Powell, W. D., Potter, J. F., Mayhew, H. C., & Nunn, M. E. (1984). The structural design of bituminous roads.
Standard, B. (1995). Code of practice for strengthened/reinforced soils and other fills, BS 8006. British Standard Institution.
Taylor, D. W. (1964). Fundamentals of Soil Mechanics. Asia Publishing House.
Terzaghi, K. (1943). Theoretical Soil Mechanics. John Wiley and Sons.
Terzaghi, K. (1955). Evalution of Conefficients of Subgrade Reaction. Géotechnique, 5(4), 297–326. https://doi.org/10.1680/geot.1955.5.4.297
Vesic, A. S. (1961). Bending of beams resting on isotropic elastic solid. Journal of the Engineering Mechanics Division, ASCE 87(EM 2), 35–53.
Winkler, E. (1867). Die Lehre von Elastizitat und Festigkeit (on Elasticity and Fixity). Dominicus: Prague, Czech Republic.
Zaewart, L. (1983). Foundation Engineering for Difficult Subsoil Conditions. Von-Nostrand Reinhold Company Inc.