Study On The Law Of The Movement And Fracture Of "Isolated Island" Working Face Ovenburden

The thesis studies the character of overburden ,the law of distribution of abutment pressure ,etc ,before isolated island face mined and after. According to the compound beam theory confirm the load on the rock stratum, analyze the condition destroyed that the rock stratum breaks. And make out the critical area of supercritical mining and get the corresponding calculation formula. And under the supercritical or non-supercritical mining ,gain two different kinds of the largest fracture height of overburden and fracture region shape. Under the different mining area of both sides, talk about the character of overburden fracture of isolated island face, (l)the overburden fracture region links a whole, (2)the largest fracture height related to the gob area of both sides, when the both sides are larger than the critical area, the overburden fracture height of the isolated island face does not increase, when only one gob area of the both is larger than the critical area, the overburden fracture height of isolated island face mined does not increase too, but lead to increase in the other and when the gob areas of both sides is smaller than the critical area, the overburden fracture height of isolated island face mined will increase and it is relate to the whole gob area, if the whole gob area is larger than the critical area, the largest overburden fracture height and the fracture region shape is similar to that of the supercritical mining, if the whole gob area is smaller than the critical, the fracture region shape is similar to that of the non-supercritical mining.According to the character of fracture and deliver power, study relation of abutment pressure of isolated island face and the gob area of both sides. And receive the conclusion that gob area of the both sides and abutment pressure of isolated island is relate. When the gob area reaching to the critical area, the concentrated coefficient of abutment pressure increase too,. And when it is larger than the critical area, the coefficient keeps intact. Provide the calculation formula of the coefficient. According to the character of abutment pressure, receive the conclusion that the minimum size to extract is relate to the gob area of the both sides, and provide the formula. Combine the 2303 isolated island face of lining No.2 colliery, and carry on studying by numerical simulation and project example ,that prove above mentioned conclusion.