Stabilization Effectiveness of Treatment with T-Shaped Deep-Mixing Column for Low-Volume Roads

Deep-soil mixing using column elements is a widely used technology for improving soft soil properties for low-volume roads in China. The deep-mixing method has some limitations, because a high-treatment area over the entire column length makes this method expensive and impractical. On the basis of a stabilization mechanism and factors that affect column construction quality, a T-shaped bidirectional soil–cement deep-mixing column has been successfully developed and proved to be effective and economical. As part of quality control of field improvement of these columns, seismic piezocone penetration tests (SCPTUs) were used. The tests can provide near-continuous measurements of tip resistance, sleeve friction, and pore pressure induced during the penetration. This paper discusses field SCPTUs that were performed in the untreated soils and the interpile soils between the T-shaped bidirectional soil–cement deep-mixing columns at the Huzhou lacustrine clay site in China. Soil properties estimated from the SCPTU data both before and after improvement methods were compared to assess the effectiveness of soil improvement. These results indicate that the use of SCPTUs will improve understanding of the changes in soil behavior achieved by this novel deep-soil mixing method for low-volume roads.