Abstract
The width of an abandoned roadway has a great influence on the roof stability of the working face. According to the coal seam conditions of the 30106 working face in the Sanyuan Shiku mine, the advance of a working face through an abandoned roadway was studied by using theoretical analysis, similar material simulation, numerical simulation, and field testing to determine the law of stope roof fracture migration, the stress distribution characteristics, and the variation in support resistance. Several conclusions are drawn: (1) The roof of the overlying strata is fractured at the edge of the abandoned roadway in front of the coal pillar and rotates downward due to the run-through of the plastic zone between the working face and abandoned roadway. (2) The hydraulic support working resistance gradually increases with decreasing coal pillar width between the working face and abandoned roadway, and the working resistance of the support tends to peak when the plastic zone extends to the coal, resulting in 3~4 times the normal recovery. Leakage occurred in front of the support in the caving zone. (3) The analysis of the relationship between the support and surrounding rock with the mechanical model for calculating the support load allows the derivation of the support working resistance formula for a working face passing through an abandoned roadway. (4) When the working face is excavated to expose the abandoned roadway, the shrinkage of the front column of the hydraulic support is significantly greater than that of the back column, and the stability is greatly reduced. This problem can be effectively solved when the uniaxial compressive strength of the backfill ≥2 MPa. (5) The engineering practice showed that the danger of leakage and roof fracture impact load was eliminated with the mining pressure reduction after reinforcement measures were taken in the abandoned roadway. The working face passed the abandoned roadway safely, providing the theoretical basis and guidance for coal remining under similar conditions.
Highlights
(2) The hydraulic support working resistance gradually increases with decreasing coal pillar width between the working face and abandoned roadway, and the working resistance of the support tends to peak when the plastic zone extends to the coal, resulting in 3~4 times the normal recovery
(4) When the working face is excavated to expose the abandoned roadway, the shrinkage of the front column of the hydraulic support is significantly greater than that of the back column, and the stability is greatly reduced. This problem can be effectively solved when the uniaxial compressive strength of the backfill ≥2 MPa. (5) The engineering practice showed that the danger of leakage and roof fracture impact load was eliminated with the mining pressure reduction after reinforcement measures were taken in the abandoned roadway
The production system of the working face is composed of several coal seam roadways of different sizes, which are used for ventilation, transportation, walking, and equipment assembly
Summary
The production system of the working face is composed of several coal seam roadways of different sizes, which are used for ventilation, transportation, walking, and equipment assembly. The abandoned roadway is constantly exposed in the re-mining face; because the creep damage degree of the surrounding rock in the abandoned roadway is not clear and the broken structure and stress transfer law of the overlying rock during mining are not understood, numerous roof fall and pressure frame accidents, which cause serious damage to the workers’ physical and mental health and production safety, occur [3, 4]. It is of great significance to study the characteristics of overlying rock collapse and the law of stress evolution in goafs and to seek safe and low-cost control technology for remining faces. Many rock mechanics studies related to exposed abandoned roadways in working faces have been performed [5,6,7,8,9,10,11,12,13]. The stope stability and control technology of exposed abandoned roadways in the working face are studied by means of physical simulation, theoretical analysis, and numerical simulation to provide a basis for taking corresponding prevention and control measures in the working face
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