Abstract In the context of slurry use for maintaining pressure and stabilizing wall protection during shield opening, diaphragm wall excavation and deep drilling to further prevent disaster accidents in civil engineering projects, a method to slurry using the natural weathered red-bed soil as the primary material is proposed, which is directly stirred with water without the addition of any other materials. Orthogonal tests are designed with the rate of change of the air filtration volume rate, effective airtightness time, and water content as the evaluation indexes. Fully transparent and high-pressure filter-cake airtightness tests are carried out. Results indicate the time of filter-cake formation is determined by the change rate of air filtration volume rate in the range between 0.020 and 0.025 L/(m·min)2. As regards the degree of influence on filter-cake formation, density exerts the greatest influence, followed by viscosity and less-than-1-mm-sized particle content. Further, the optimum density/viscosity/less-than-1-mm-size particle content combination of the slurry is determined to lie in the ranges of 1.83–1.95 g/cm3/13–21 Pa·s/45–60%. Moreover, it is found filter-cake damage is closely related to water content. With similar properties to the artificial, wide distribution of natural sources, low cost, and sample process, this materials is expected to be widely applicated.