Study on Comprehensive Technology of Preventing Mud Cake of Large Diameter Slurry Shield in Composite Stratum

Abstract

When large-diameter slurry shields are tunneling in a composite stratum with a high clay content, the cutter head may form a mud cake. After the mud cake is formed, it will cover the cutter and reduce the opening rate of the cutter head, thus reducing the penetration of the cutter and the driving speed. Based on a road upgrading project, this paper studies the prevention and treatment of a mud cake and forms a set of comprehensive treatment methods. For a large mud cake, through theoretical analysis, two calculation methods of the cutter head sealing coefficient are obtained, and the cutter head sealing coefficient relationship model is established. Comparing the calculated cutter head’s actual opening coefficient with the required cutter head opening coefficient can provide a judgment basis for the time of manual warehousing. For medium and small mud cakes, the numerical simulation is carried out based on the cutter head and the scouring system, the distribution characteristics of the flow field near the cutter head are analyzed, and the angle of the central scouring hole is optimized. For a small mud cake, hydrogen peroxide is selected as an additive through microscopic mechanism analysis. The effect of the hydrogen peroxide solution concentration on dissolving a mud cake is obtained through laboratory tests, and its effectiveness is verified through field tests. The research results can provide a reference for the mud cake prevention of slurry shields in similar strata.