Analysis on Failure Mechanism of Rock-Coal Two-Body Structure with Weak Cemented Rock and the Condition of a Gob Side Entry without Coal Pillar

Abstract

Though the real tri-axial testing simulated by FLAC3D, the failure mechanism and deformation process of rock-coal “two-body” structure in the in-situ area, named crucial point, which bore the ultimate lateral abutment pressure and broke in the beginning to lead to the whole damage of the “three soft” ground-rock around the gob-side entry retaining was obtained, and the relationship between the ultimate strength and cohesion of rock was obtained. By field observation the condition of gob side entry without coal pillar was obtained: top old roof as the bearing body, when the height of direct roof was larger than 1.309m1 and soft enough, the half-arch structure could made by the upper strata of the direct roof, as a weak layer, which gave a force straight up against to the old roof overturning and sinking. That was the condition of gob side entry retaining without coal pillar.