Experimental study of salt-resisting slurry for undersea shield tunnelling

•XG improved the filtration and rheology of seawater mixing slurry.•In 100% seawater condition, the XG content should be controlled at 0.3% in mass.•Seawater slurries with 0.3% XG added have good penetration effects in the strata. For undersea shield tunnelling projects, selection of a suitable slurry ingredient is a challenging issue due to the presence of massive ions. As a result it may be adverse for the formation of filter cake at the tunneling face, which would lead to a face instability. Using xanthan gum (XG) as an addictive to traditional sodium bentonite slurries was proposed in this paper. SEM images revealed that XG utilize its ‘wrapping effect’ to effectively alleviate the decrease in the Russian funnel viscosity caused by electrolytes present in seawater and to improve the control of water loss. The influences of XG contents on slurry properties under different salty water conditions were explored through a series of laboratory tests. When the seawater content exceeds 30%, the change in XG content required to maintain the basic properties of the mud is insensitive to increase in seawater content. The quality of filter cake and infiltration features of the developed slurries under medium coarse sand and fully-weathered rock strata conditions were evaluated through slurry infiltration tests. It was found that the bentonite water ratio is mainly related to the properties of the strata, and XG content is determined by the seawater content.