Evolution of rheological behavior in coarse-grained gangue slurry under multi-condition shear: regulation mechanism of particle-floc-water tri-skeleton

During pipeline transportation, coarse-grained gangue slurry (CGS) experiences different working conditions (such as straight pipe transportation, curved pipe transportation, pump start, and pump stop) and is subjected to different shear forces, resulting in complex rheological behaviors, transportation properties and resistance loss of CGS. To accurately control the transport performance of CGS, research on the rheological properties and microstructure mechanism of CGS is urgently required. In this study, the rheological properties of CGS under different shear conditions were tested, the environmental scanning electron microscopy (ESEM) tests, low-field nuclear magnetic resonance (LF-NMR) tests and Zeta potential tests on CGS samples were carried out, and the microstructure characteristics, water migration laws, and Zeta potential distribution laws were analyzed. Additionally, the microstructure mechanism and key regulatory factors of rheological properties were obtained. The research results show that CGS has staged rheological properties, shear-thinning properties, thixotropic effects and time-varying properties. The greater the proportion of fine-grained gangue, the more obvious the shear-thinning characteristics. The plastic viscosity decreases by 45.24% after thixotropy. The main state of water in CGS is the pore water, with a content of over 80%, and a smaller portion consists of adsorbed water and free water. A three-framework composition structure of gangue particles, flocs and water was proposed. The key regulatory factors for CGS’s fluidity are coarse-grained gangue, flocs and pore water, and the key regulatory factors for its stability are coarse-grained gangue, flocs and adsorbed water. This research provides a theoretical basis for the regulation and optimization of the transportation performance of the CGS.