A Study on the Floor Heave Characteristics of a Gob‐Side Entry in Deep‐Thick Coal Seam During Longwall Mining

Floor heave control becomes more and more prominent in engineering practice with the increased mining depth of the working face. The gob‐side entry of the 21404 working face in Hulusu Coal Mine was taken to be the engineering background to study the gob‐side entry’s floor heave in the working face with a deep, thick, and dense layer of coal. There was slight floor heave in the gob‐side entry before mining the working face, and cracks appeared in the hardened bodies of the floor. The floor heave amount increased significantly before squaring. The roadway’s middle floor was heaved, and the highest floor heave was about 500 mm. The floor heave of the return‐air entry increased significantly after squaring. It was squeezed from the two sides to the roadway’s middle part. Additionally, there was floor heave in the roadway’s middle part. The deformation of the roadway was accelerated when it was less than 90 m away from the working face, with a maximum floor‐heave amount of 500 mm and a maximum two‐side convergence of 300 mm. The amount of floor heave was greater than that of the two sides. There was an oblique triangular displacement area at the roadway side’s bottom in the gob‐side entry. Coal on the solid sides moved to the roadway. The gob‐side entry’s floor heave was serious, with coal pillars’ extensive deformation on the sides.