Employee was pumping ""glue"" into the mine roof near the 11 Rt longwall face in the belt entry. As EE pumped the glue into the roof, a slab of rock/headcoal about 3'x4'x1' thick fell out between existing roof straps. The falling rock struck EE across back. EE stated that EE felt a pulling sensation in back. EE was brought out and transported to the hospital.