To mitigate the risk of cutterhead “cake formation” during shield tunneling in clay strata, optimizing muck conditioning parameters is essential for ensuring construction efficiency. This study presents a systematic investigation focused on the ②-7 soil layer of the Longquan inverted siphon project in the Central Yunnan Water Diversion. First, a dispersive foaming agent was selected through performance tests, and the basic conditioning parameters were determined. Subsequently, combined with slump tests, the influence of moisture content and foam injection ratio (FIR) on the plastic flowability was analyzed, leading to the final optimized parameters: w=38.2% and FIR=40%. A field trial was then conducted using rings 876~900 as a test section, comparing performance between optimized and non-optimized zones. The results indicate that: (1) The slump of the conditioned muck increased from <7 cm to 8.9 cm, indicating significantly improved flowability; (2) The total thrust of the shield decreased by 5.3%, with the average value dropping from 8 788 kN to 8 326 kN; the average cutterhead torque reduced by 26.1%, from 1 270 kN·m to 938 kN·m; and the advance rate increased by 18.4%, from 55.6 mm/min to 64.8 mm/min; (3) The dispersion of the total thrust was significantly reduced, with the standard deviation decreasing from 915 to 367, a reduction of 60%. This parameter scheme effectively suppresses the risk of “cake formation” by reducing the adhesiveness and shear resistance of the muck, providing a technical basis for shield tunneling in clay strata.