A Comprehensive Review on Current Design Methods Used to Design Controlled Modulus Columns

Ground improvement using Controlled Modulus Columns (CMC) is an innovative technique, which is gaining momentum in Australia and many other parts of the world. Since there are no ground vibrations generated during the construction, this technique is highly appropriate for urban environments. Another added benefit is that the soil cuttings produced during the construction are eliminated, which is beneficial when dealing with contaminated sites or landfill sites. The installation stages of CMC, especially the auger penetration and grouting, contribute to forming a disturbed zone known as a smear zone around each column with increased stiffness and strength compared to in situ ground. It is identified that this smear zone is highly beneficial to the load-carrying capacity of columns. However, no research has been conducted so far to understand the smear zone effect and the significance of the smear zone on the load transfer mechanism of the column-improved ground and it has not been included in the current design practice. Therefore, this paper presents, background information, including an introduction to the context of CMC and the load transfer mechanism of CMC. Also, a review of current design methods adopted in practice is presented, including the design recommendations proposed by the ASIRI national project for rigid inclusions, which is the first-ever design guideline for the CMC improved ground.