Abstract: The roof mechanical characteristics in high horizontal stress roadway in the western mining area is simplified as a problem of rock sample containing the lengthways fissure under uniaxial compression. The strength, deformation and failure mode of sandstone which is chosen are discussed. The results show that, with the increasing of fissure length, peak strength and peak strain of sandstone containing a lengthways fissure first decreases and then rises slightly, and reaches the least value when the fissure length is 42 mm. Lengthways splitting failure in sandstone samples occurs along the prepared fissure tip, but the heterogeneity has an obvious influence on the number of main secondary crack and crack extending path. Comparing with the no-filling sandstone, gypsum filling is not apparent to the promotion of sandstone strength containing lengthways fissure; while the high strength cement has a good reinforcement effect with average peak strength increasing by 22.27%. The research achievement has a positive significance on the development of rock mechanics and the surrounding rock stability controlling theory in the western mining area.

Key words: roof, lengthways fissure, mechanics characteristic, fissure length, filling