Abstract:The pore structure of the thickening compaction region are the key factors affecting the underflow concentration of gravity thickening, the quantitative study of its geometric characteristics is rare. The morphology and distribution of pores under shear action are obtained by means of CT tomography and 3D reconstruction technology, analysis the change characteristics of porosity, Feret diameter, pore circularity and so on, reveal the evolution law of the shear action on the pore structure of the high concentration bed of unclassified-tailings. The results show the porosity under the 2rpm shear action decrease by 13.43%, but the change of average number of pores is not obvious; the pores is mainly concentrated at 0-20 μm of Feret diameter with/without shear action, occupying 30.67% and 46.07%. The shear action reduces the pore circularity by 9.86% in the 0.9-1 range, but the changes in the aspect ratio and flatness are not obvious; the pore number decreased by 14.45% in the range of roundness in 0.45-0.5 and 0.95-1.0. Therefore, the shearing action can reduce the porosity of the tailings compacted bed and decrease the number of pore Feret diameters in the 0-20 μm, but it has little effect on the average number of pores; shear action can reduce the number of pore circularity in the region of 0.9-1, but there is no obvious effect on aspect ratio and flatness, it has great influence in the roundness of 0.45-0.5 and 0.9-1.