With the expanding scale of mining exploration and mining，and the increasingly serious environmental problems associated with mining，abandoned tailings and mined-out areas have become major hazards in mine safety construction.The traditional low concentration tailings surface accumulation treatment will not only cause land pollution，but also be eroded by rainwater，aggravate the cracking of tailings reservoir，and there are hidden dangers of dam break.Paste filling technology is a green tailings disposal technology，which can not only save land resources，but also protect the ecological environment by disposing of abandoned tailings.The research results show that the strength of tailings filling body is positively correlated with slurry concentration in a certain range.Therefore，by increasing the concentration of tailings filling slurry，the amount of cement can be greatly reduced，and the cost of tailings disposal can be reduced.The key links of paste filling technology of unclassified-tailings are concentrated dehydration of fine tailings and paste preparation.Distribution characteristics of diversion channel in dense bed and micro-seepage mechanism in channel are key factors affecting gravity concentration effect of unclassified-tailings.The raw material of the unclassified-tailings comes from vanadium iron ore flotation tailings.The flocculation settling and shearing experiments of the unclassified-tailings were carried out on a self-developed intelligent small continuous densification test platform.The effect of shearing on the pore distribution characteristics of the bed was studied by combining the continuous densification test with CT scanning technology.The rotation of the scraper at the bottom of the thickener breaks the static balance between particles and water，connects the pore and discharges the closed water to form a high concentration underflow. Samples were obtained by in-situ sampling-quick freezing-freeze drying process for CT scanning test.The image results obtained by CT scanning were segmented，denoised and binary processed by ImageJ image processing software.Then the results were imported into COMSOL Multiphysics software to simulate the law of reverse seepage of liquid in the bed.Finally，the influence of shear on drainage process was revealed by analysis. The results show that when the feed concentration is 10% and the flocculant concentration is 0.01%，the average concentration is 50.10% wt and 55.82% wt respectively under the continuous dense condition without/with shearing，and the internal porosity is 49.90% and 44.18% respectively，indicating that shearing can increase the average concentration while reducing the internal porosity.The number of diversion channels under non-shearing and shearing is 6 and 2 respectively.The shearing reduces the number of diversion channels by 66.7%，the number of outflow channels by 6 and 1 respectively，and the number of outflow channels by 83.3%.The maximum seepage velocity of the liquid in the channel is 9.574×10^-6 m/s and 2.592×10^-6 m/s respectively，and the maximum flow velocity at the outlet is 5.372×10^-6 m/s and 1.468×10^-6 m/s respectively.The maximum pressure on the pore surface decreases gradually with the reverse seepage of the liquid.Before shearing，the channel is open and connected.After shearing drainage，the pore volume decreases，the channel closes，and the bed concentration increases further.Adding shear action can increase the concentration of tailings and decrease the porosity of tailings，which has a great impact on the channel.The enhanced drainage mechanism under the shear condition studied in this paper will provide theoretical support for the dense dewatering of tailings mortar and lay a foundation for the preparation of high-concentration tailings mortar.