In Situ Test on Pre-Mixed Fluid-Solidified Soil Pile for Embankment Foundation Treatment

Cement–soil mixing piles commonly face the problem of insufficient pile quality during on-site construction, and traditional measures such as increasing grouting pressure or enhancing mixing intensity are difficult to resolve effectively. The development of flowable solidified soil technology offers a new path for innovating soil pile reinforcement techniques. Based on an in situ test, this research proposes and introduces a new technology for pre-mixed fluid-solidified soil piles (PSPs). This technique effectively improves pile quality and significantly enhances pile bearing capacity by pre-mixing flowable solidified soil and then grouting it after pre-drilling holes with a screw drill. The results show that reinforcement of soil piles using the pre-mixed flowable solidified soil and pre-drilled grouting process has significantly improved pile quality, with better core sample integrity and uniformity. The results indicate that the characteristic bearing capacity of the uniform-section PSP is 252 kPa, meeting the design requirement of 130 kPa. The ultimate bearing capacity of the uniform-section PSP is 177% higher than that of the uniform-section CMP. In addition, the ultimate bearing capacity of the PSP after variable-section treatment is 153% higher than that of the uniform-section PSP. Finally, new design recommendations have been proposed, specifically calculation formulas for the load-bearing capacity and settlement of composite foundations based on current standards.