OasisLMS

This report summarizes a comprehensive, multi-phase research project funded by the DFI Committee Project Fund and conducted in collaboration with industry experts. The project examines how in situ overburden stress during curing influences the strength of deep mixing method (DMM) materials and contrasts these conditions with those of standard quality control tests. Findings from laboratory bench tests, field-modified oedometer tests, in situ DMM column tests and independent review of coring data demonstrate a significant correlation between in situ overburden stresses and unconfined compressive strength (UCS). In particular, the findings indicate that fine-grained soils experience greater strength gains under field stress conditions than granular soils. The study also delves into the drainage, consolidation and interparticle behavior of DMM materials, proposing empirical and analytical methods to adjust in situ strength measurements for a more accurate assessment of material properties in practical applications. The results of the study indicate that the mechanical properties of DMM soil-cement materials are generally underestimated due to traditional curing and testing at ambient conditions, ignoring the confining stresses found in natural settings.

Keywords: deep mixing method, unconfined compressive strength, curing stress, soilcement mixed material

George Onorato, P.E. and Giovanni Bonita, Ph.D., P.E., P. Eng., P.G.

Research Report