New Backfill Material Applied to High Roof Falling Zone of Ultra Thick Seam Gateway

In order to solve the highroof falling zone danger problems of the mining gateway occurred in the fully mechanized top coal caving mining in thick seam, based on the analysis on the cause of the high roof falling zone and danger, a new backfill material of high roof falling zone was developed.In combination with the cert ain conditions of the high roof falling zone in the gateway, a suitable backfill technique was selected.The site application results showed that the backill material could have the features of the material with the light weigh and non-combustion, the compressive strength after three days could reach at 1.4 MPa and the sweling rate could be 6%8%. The borehole sight showed that the backilled material in the high roof falling zone was compact with no crack and broken and the backfilled material were wel I bond with the roof of the high roof falling zone. Under the influences of the periodical pressure and mining activities, there were no deformation and bedding occurred i n the backilled material of the high falling zone.The backfill material and the backill technique could well solve the existed problems of the high roof falling zone.