Abstract: Scientifically and reasonably determining the thickness of the mine′s waterproof pillar is a prerequisite for safe production in the mine,which can protect the safety of houses and roads on the surface and prevent the generation of waterconducting fissures that can penetrate the Quaternary aquifer during mining.The load transfer intersection line method,K.B.Lubeneyita estimation method,and fracture zone height estimation method are used to calculate the thickness of the waterproof pillar.The thicknesses obtained by the three theoretical calculation methods are 14.3～17.3 m,17.5～31.4 m and 41.8～57.4 m respectively,so the thickness of the Waterproof pillar is 60 m.Numerical simulation shows that under the premise of a 60 m thick waterproof pillar,the maximum tensile stress generated in the mining area and pillar is about 0.47 MPa,and mining will not cause damage to the waterproof pillar.In the simulation results,the maximum horizontal displacement of the ground surface is about 5.8 cm,the maximum vertical displacement is about 26.5 cm,the maximum tilt is 1.70 mm/m,the maximum curvature is 0.20 mm/m2,and the maximum horizontal deformation value is 0.70 mm/m,which meets the relevant specifications Requirements to ensure surface safety.

Key words: waterproof pillar,building (structure),theoretical calculation,numerical simulation