Abstract: As a new type of intervention technology for hyperbaric conditions, the saturation intervention method has the advantages of high efficiency and security; the key to success of this method is the formation of a good, airtight filter cake. Based on the Nanjing Weisan Road river-crossing project, and considering that effective working time inside the chamber is about 3 to 4 hours, on-site tests were carried out regarding slurry preparation, formation of the filter cake and air tightness, and a slurry performance index was determined for each stage of filter cake formation. Relevant quantitative judgment standards are summarized in this paper.