Mechanism Research On Blasting Damage And Instability Of Thin-layer Complex Roof And Its Concorl Technology

The coal of excavation scope was blasted by impact force of explosion while blasting driving roadway and that caused serious damage even destruction to the thin-layer complex roof. Therefore the damage process of the thin-layer complex roof was researched while blasting driving roadway and that have a great significance to control stability and roadway support. The thin-layer complex roof was researched according to Dongrong 2^nd mine's geological condition, theoretical analysis, numerical simulation analysis, field measurement and industrial test was adapted synthetically to research the mechanism of the roof damage instability and the technology of stability control for roof. The following conclusions on the basis of the above research work:(1) The damage of layer rock developed with obvious direction in the explosive loading, interaction of stress wave and the structure of rock is the main factors for layer rock to crush and fissures developed. The roof experienced abutment pressure in front of coal face, then a stress concentration area was formed; the weak plane and fractures was deteriorated, so the roof easily appeared damage instability state due to abutment pressure in front of coal face, blasting stress wave impact and stress redistribution of interaction after excavation.(2) The degree of the blasting pressure effect on the roof was increased significantly in the gravity and horizontal pressure. With the horizontal pressure coefficient increasing, the compressive stress of the roof was increased and the tensile stress was decreased; the blasting vibration of the roof in front and behind of the driving face was decreased, and the blasting vibration of the roof Just above the driving face was increased. (3) With the dynamite increasing, the degree of the pressure and vibration velocity effect on the roof near the explosion was more than that of the roof far form the explosion. For the same thickness of the roof, the more layers of the roof the more blast wave weakens seriously.(4) The results of blasting vibration and sound velocity test indicated that the measured vibration velocity and the simulation results have good agreement on the whole. The blast damage of roof was increased as the blasting time increasing, The test results show that the roof damage scope between 0m and 3.6m and the most likely to delaminate at point of 0.6m and 2.4m of the drill hole.(5) The stability of the roof has greatly improved after combination supported by the anchor, strip, and spray aiming at Dongrong 2nd mine's roadway.It is important role to the safety and stability of roadway which the tensile strength of rock was estimated correctly, blasting parameters shoule be optimized and the way of supporting method all this can effectively control the damage of the thin-layer complex roof while blasting driving.