Model tests on performances of DSM and CS-DSM piles

Using the small-scale model rig, a comparative experimental study is conducted to investigate the process control and quality control in the deep soil mixing (DSM) method and contra-rotational shear deep soil mixing (CS-DSM) method. The research emphasis is placed on the effects of cement content, blade rotation number T on the uniformity and unconfined compression strength (UCS) of mixing piles. A notably improved uniformity and continuity of the CS-DSM piles over the DSM piles is confirmed by the test results. The strength ratio R_s ranges from 1.41 to 6.4, and it shows an exponential decrease with the increasing T. Furthermore, the results from 24 model piles provide insights into the fundamental relationship and distinctions between UCS and T. On this basis, the construction parameters can be optimized to ensure the target design strength for both types of piles. The model test results clearly demonstrate the differences in the construction quality between the DSM method and the CS-DSM method. The technical basis established in this study serves as a cornerstone for the process control and quality assurance in installing high-quality CS-DSM piles.