Ground Improvement of Sabkha Soil Using Controlled Modulus Columns (CMC): A Case Study in Saudi Arabia

This paper presents a ground improvement approach for a project comprising a raft foundation for a substation building. The design objective was to achieve a net allowable bearing capacity of 150 kPa and to limit total settlement to 60 mm, in compliance with the Saudi Building Code (SBC). Subsurface conditions revealed the presence of weak, compressible Salty Sabkha soils that are unsuitable for shallow foundations without improvement. While traditional deep foundation systems such as piles were initially proposed, Controlled Modulus Columns (CMC) were suggested as a cost-effective and environmentally sustainable alternative. The CMC technique enhances soil stiffness and reduces settlement by introducing rigid inclusions without full soil displacement. The performance of the improved ground was verified through Zone Load Test (ZLT). The CMC system meets bearing and settlement requirements. ZLT results showed a maximum settlement of 6.29 mm at 225 kN/m2, which met the project requirements and confirmed the efficiency of the proposed ground improvement technique. In this case study, the CMC solution was not only effective in settlement control but also in cost and carbon footprint reduction. However, further validation under varying soil and loading conditions would strengthen the general applicability of the findings.