Multiscale study of thixotropic slurry for pipe-jacking construction

To address poor rheology, pumping challenges, and interfacial instability during pipe-jacking through sandy-spoil, this study develops a sodium polyacrylate (PAA)-modified bentonite slurry and establishes an integrated macro–micro–nano multiscale analytical framework. At the macroscopic level, an orthogonal design systematically evaluates fluid loss, Su’s funnel viscosity, bleeding rate, and friction coefficient; the results indicate that 12-14% bentonite with 0.3-0.4% PAA simultaneously achieves low fluid loss, near-zero bleeding, and pronounced friction reduction while keeping viscosity within the pumpable range. At the microscopic level, TEM reveals a transition from a dense, agglomerated state to a flexible, lubricated state; PAA forms a coating layer and lubricating film that enhance particle dispersion and flow, strengthen thixotropic recovery, and thereby optimize structural stability and rheological performance. At the nanoscale, MD elucidates a cooperative interfacial mechanism: PAA and water assemble on mineral surfaces into a stable hydrated/lubricating layer, where weak interactions strengthen particle-water-polymer coupling, accounting for the macroscopic improvements in friction reduction and stability. Overall, PAA modification enables coordinated “lubrication-water retention-interface stabilization,” providing experimental evidence and mechanistic support for optimizing pipe-jacking slurry formulations.