Research on reasonable width of waterproof coal pillar when mining under the unconformity strata

The seam and quaternary are angular unconformity. In order to prevent water flowing fractured zone of overlying strata connected quaternary, it is necessary to set a certain width of the lateral waterproof pillar. Analyzed the discipline of fractured zone above mine goaf with empirical value of waterproof coal pillar by the method of UDEC^2D numerical simulation. The result of numerical simulation showed that water flowing fractured zone connected unconformity surface with waterproof coalpillar’s empirical value. Supposed the shape of the water flowing fractured zone on both sides of the work-face was semicircular. Revised the empirical formula for vertical waterproof coal pillar, and deduced the new formula of lateral waterproof coalpillar’s reasonable width. The new formula provides basis for setting lateral waterproof pillar. In the vertical direction, by adjusting the length of work-face, made water flowing fractured zonedon’t connected with quaternary under the pillar width computed by new formula.WT