In recent years, cement deep mixing (CDM) columns have been widely adopted as a ground improvement solution for enhancing the stability of excavation bases in the basement construction of high-rise buildings on soft soils in Ho Chi Minh City. This technique plays a vital role in improving the mechanical characteristics of soft soils, including unit weight, shear strength, and elastic modulus. A total of 580 CDM samples were collected by core drilling from 65 in-situ CDM columns. Unconfined compression tests were carried out to determine the unconfined compressive strength qu, elastic modulus E50, and unit weight γCDM of the CDM columns. The study aims to assess the critical engineering properties of CDM columns, with emphasis on qu and E50, in the context of deep excavation for basement construction. This study investigates the correlation between the unit weight of natural soil and that of CDM columns, evaluates the E50/qu ratio. The findings of this study provide a practical framework for engineers to assess potential risks and enhance the reliability of design and construction practices for multi-basement structures with excavation bases reinforced by CDM columns.