Abstract: Due to the enrichment of a soluble salts and various metal cation components in seawater, seawater slurry shows large specific gravity, low colloidal rate, poor stability and high water loss, and does not meet the requirements of slurry shield construction. In order to modify the seawater slurry to maintain the stability of the excavation surface and reduce the construction cost of the shield tunnel, eight additives, such as CMC, cellulose PAC, and ammonium polyacrylate, etc., were used to test the properties of seawater slurry. The additives which modified the seawater were selected, and the influence law of the additives amount and time on the properties of the seawater slurry was analyzed. At the same time, the modified seawater slurry formation penetration test was carried out based on the preferred additive CMC using a mud film formation test platform. Results show that different additives have significant differences in the properties of seawater slurry. The cellulose PAC and CMC have better modification effect on seawater slurry. The turbid layer, mixed layer and flocculated sediment layer appear in 24 h. The amount of water filtered by the seawater slurry to the formation is greater than that of the modified seawater slurry, and the slurry skin is slightly thicker, but it is sparse. It can be speculated that the additive neutralizes part of the seawater component and flocculates and precipitates, and the excess additive exhibits a thickening effect on the pale cement slurry.

Key words: submarine shield tunnel, property change of seawater slurry, infiltration experiment of slurry, slurry film quality, colloidal rate