Wall slip behavior of cemented paste backfill slurry during pipeline based on non-contact experimental detection

Wall slip is a microscopic phenomenon of cemented paste backfill (CPB) slurry near the pipe wall, which has an important influence on the form of slurry pipe transport flow and velocity distribution. Directly probe the wall slip characteristics by conventional experimental methods is difficult. This paper built a non-contact experimental platform for monitoring the microscopic slip layer of CPB pipeline transport independently based on particle image velocimetry (PIV), analyzed the effects of slurry temperature, pipe diameter, solid concentration and slurry flow on the wall slip velocity of CPB slurry, which refined the theory of the effect of wall slip characteristics on pipeline transport. The results showed that CPB slurry had an extensive slip layer at the pipe wall, with significant wall slip. High slurry temperature improved the degree of particle Brownian motion within the slurry and enhances the wall-slip effect. Increasing pipe diameter was not conducive to the formation of the slurry slip layer and led to a transition in the CPB slurry flow pattern. The increase in solid concentration increased the interlayer shear effect of CPB slurry flow and the slip velocity. The slip velocity value increased from 0.025 m·s^-1 to 0.056 m·s^-1 when the solids content improved from 55wt% to 65wt%. when slurry flow increased, CPB slurry flocculation structure changed, which affected the slip velocity, and the best effect of slip layer resistance reduction was achieved when the transported flow rate was 1.01 m3·h^-1. The results had important theoretical significance for improving the stability and economy of CPB slurry in pipeline.