A statistical model for the unconfined compressivestrength of deep-mixed columns

E. J. Chen Y. Liu F.-H. Lee

Abstract：The strengthof soil improved by deep mixing processes often exhibits significant spatialvariability. This paper presents a statistical model for strength distributionin deep-mixed columns, based on the assumption that spatial variation instrength arises from spatial variation in binder mass fraction. The statisticalinputs of the model are the probability density function and coefficient ofvariation of the binder distribution, both of which were obtained fromcentrifuge model data and were assumed to be independent of the amount of thebinder introduced into the ground. The theoretical framework of the model isfirst developed, followed by an assessment of the probability density functionfor the binder distribution. The variation of binder mass fraction within adeep mixing column is fitted by a truncated normal distribution. The model isbenchmarked against core strength data from three phases of deep mixingoperation in a construction project. The simplicity of the model precludesconsideration of the effects of detailed mixing blade configuration, in situvariation in soil properties as well as workmanship. In spite of this, thecomputed histograms of strength distribution gave a reasonable reflection ofthe measured strength distribution. This suggests that despite the variety andcomplexity of deep mixing processes, one may still be able to develop a simpleand workable model of the strength distribution taking into account just a fewimportant factors.

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http://www.icevirtuallibrary.com/doi/full/10.1680/jgeot.14.P.162