Statistical evaluation of the overall strength of a soil-cement column under axial compression

Deep mixing and jet grouting with cement hardening agent are widely used techniques for soft ground stabilization. In a soil-cement column, however, the unconfined compressive strength is generally of significant heterogeneity. In this study, the heterogeneity is considered as two components: a deterministic mean trend and a zero-mean random field. Finite element analysis is used to model a soil-cement column subjected to axial compression, and spatially random values of strength parameters are assigned at the integration points to simulate this heterogeneity. The results of the analysis show that the overall strength of a soil-cement column is proportional to the volume-averaged unconfined compressive strength of the column. It is also observed that the volume-averaged unconfined compressive strength can be successfully predicted by the unconfined compressive strength at the distance of two-thirds of the radius within a soil-cement column. This prediction can mitigate the difficulty in determining the deterministic mean trend. On the other hand, the relationship between the statistical characteristics (e.g. average and variance) of the overall strength and those of the unconfined compressive strength is examined, whereby a simple procedure is proposed to estimate the former from the latter. This procedure is exemplified in the estimation of the specific strength of a cement-treated soil.