Analysis on Fracture Mechanics Theory of Roof Cutting Mechanism of Shallow-Buried Working Face Crossing the Uphill Sections of Valley Terrains
When a shallow-buried coal seam working face is advanced to the uphill section of a valley terrain,it is prone to large-scale dynamic mining pressure disasters caused by the overall sliding and instability of key layer fracture blocks along the coal wall.According to the fracture characteristics of the roof in the uphill section of the valley terrain,a mechanical model was constructed based on the fracture mechanics analysis method,and the mechanical mechanism of roof instability and the basic roof fracture instability conditions were discussed.The calculation formulas for the roof weighting step and the working resistance of the support were obtained,and the key disaster causing factors were analyzed.The research results show that the concentrated stress and stress intensity factor at the crack tip of the basic roof in the damaged zone increase as the working face advances,and when the stress intensity factor increases to a critical value,the cantilever beam breaks and the working face is compressed.The size of the valley slope angle has a major impact on the weighting step and the working resistance of the support.Factors such as the crack length,the basic roof thickness,and fracture toughness in the damaged zone also have significant impacts.Through on-site monitoring at the 2103 working face of Madiliang Coal Mine,the theoretical analysis results were verified,and the reasonable value of support resistance was further analyzed.The research work has improved the accuracy of roof control of the working face crossing the uphill section of the valley terrain,which can effectively promote the safety production of the mine.
Shallow-buried coal seamValley terrainUphill sectionFracture mechanicsWorking resistance of the support
万方数据
维普
