In the dynamic water environment, grouting requires a material with higher strength and anti-washout performance to prevent groundwater inrush. This study aims to develop a dynamic water slurry by mixing polypropylene fiber (PP fiber), silica fume (SF) and the polymer material of redispersible emulsion powder (REP) to the Portland cement. Towards this aim, a series of tests, including strength, gel time, bleeding rate, fluidity, and anti-washout, were conducted to evaluate the effects of SF, PP fiber, and REP on the slurry properties. The test results show that: (1) SF displays significant effects on strength, gel time, fluidity, and bleeding rate of cement slurry. Differently, PP fiber mainly affects the stress–strain behavior of the slurry and can improve the ductility significantly. (2) By mixing SF and fiber simultaneously, the slurry strength can increase by about 30%, and its strain can extend by more than 70%. Meanwhile, the composite slurry possesses great anti-washout properties at a low flow velocity (v ≤ 0.4 m/s), and the grouting retention rate (GRR) can reach up to 98.7%. However, the GRR decreases to a maximum value of 31.3% when v = 0.6 m/s. (3) By mixing the REP into the fiber-SF composite slurry, the GRR can further increase, reaching more than 60% even when v = 0.6 m/s. As a result, the developed fiber-SF cementitious composite slurry, which when mixed with REP, presents a favorable performance in the dynamic water environment.

With the continuous mining, a huge amount of mine waste has accumulated in tailing dams in China. The increasing frequency of abnormal rainfall in China poses a significant threat to the stability of tailings dams. It is important to study spatial variation of physical and mechanical properties of tailings for the process of dam destabilization due to rainfall. The Luomukeng tailings dam, Jiangxi province, China, was selected as the research object and the changes of physical parameters of tailings at different spatial locations under different rainfall intensities and influence on the tailing’s mechanical properties were studied. The correlations between the parameters were analyzed by Spearman correlation analysis. The results showed that rainfall led to particle migration, with a high number of fine particles repositioning. The greater the intensity of rainfall, the more significant the migration of particles, the more obvious the changes of physical and mechanical properties of tailings. Based on Spearman correlation analysis results, it was obtained that the change of inhomogeneity coefficient of tailings has the strongest effect on cohesion, and the change of water content has the strongest effect on friction angle.