Abstract: To study the blockage mechanism of ground transport pipeline for isolated overburden grout injection,the operation condition of the slurry pipeline was monitored. Based on the measured data,the blockage of the slurry pipe-line was divided into three types:adherent type,sedimentary type and comprehensive type. The formation mechanism of three types of blockage was revealed by the theoretical analysis and experimental verification of the rheological proper-ties of pulverized coal ash and the hydration reaction of fly ash. The influence of pipeline roughness,chemical composi-tion and flow rate on all kinds of blockage was analyzed. The results show that the adherent type was mainly influenced by the formation rate of fly ash hydration reaction gelation compound and velocity of the slurry. The sedimentary type is mainly caused by the low velocity of the slurry. In view of the above,some suggestions for preventing pipeline blockage were proposed by the authors.