Abstract: In the process of EPB shield tunneling in large pebble stratum, it is necessary to improve the muck in the soil according to conditions including different stratum, groundwater level, construction process. Taking the first phase project of Chengdu Metro Line 18 as an example, through laboratory tests and theoretical analysis, the flow plastic state, low permeability, and low internal friction angle of the ideal EPB shield muck in sandy pebble stratum are determined. Five muck improvement solutions are put forward, and relevant tests are carried out to analyze the muck improvement effect. Through field practice verification, multiple muck improvement measures are put forward, and new viewpoint of optimal improvement solution is obtained.Test results show that the optimal solution for the improvement of large particle size sandy pebble stratum muck is bentonite slurry plus foam agent or bentonite slurry containing polymer.