Study On The Safety Protection Theory And Technology Of Explosion Doors For Vertical Shafts In Coal Mines

Explosion doors in coal mine ventilation systems are a kind of indispensable security equipment used to protect mine main fans from damage in the event of an explosion.It is indicated by the practice of mine accidents rescue that there are potential flaws and security problems in existing explosion doors of China.It is presented outstandingly as explosion doors are easy to damage and even thrown into the air in the explosions.Once the existing explosion door is damaged or thrown in the sky,it's nearly impossible to reset and cover shafts again,which can lead to mine ventilation corruption and disastrous consequences for rescue and relief work.Within the field of the safety protection of explosion doors,the key scientific and technical issues was studied in this paper,which includes the possible blast load on explosion doors,the methods and rules of preweakening of the blast wave in air shafts,the laws of explosion venting of explosion doors,the design of the new-type explosion doors,and so on.The main innovative achievements made are as follows:According to the maximum height of thrown explosion doors in some typical large explosion accident cases and the damage load of blades of main ventilation fans,an indirect method for calculating the possible blast load on explosion doors has been developed.On this basis,a triangular blast load with an overpressure of 300 kPa and a duration of 20 milliseconds is recommend as a standard load for explosion resistance design of blast doors.To reduce explosion resistance design difficulty of explosion doors and enhance the protection to main fans and other ventilation devices or facilities,a series of methods and views of weakening the blast wave by blind lanes and detours are proposed.On the basis of numerical simulations,the characteristics,laws and key factors of various methods of eliminating shock waves are found.Further research also shows that different shock weakening methods follow the same principle: the shock wave energy is redistributed and homogenized in time and space.The numerical simulation shows that the overpressure peaks of the blast in a 20-meter long blind alley model and a 47.5-meter long detour model are relatively reduced by 18% and 45%,with the specific impulse reduced 25.6% and 46%.Multiple common phenomena and laws of the dynamic behaviors of explosion doors in the process of explosion venting are revealed.It is found that there exists an apparent turning point in the curves of velocity and acceleration to time of explosion doors.This phenomenon is the reflection of the interaction between the blast wave and the explosion door.Balance weights and wire ropes are in a weightless and out of control state,which may highly likely impact the normal reset of the explosion door.The rebound effect of the buffer provides driving force for the reset of the explosion door,while the action of the flow behind shock wave front plays the cushioning effect to the reset of the explosion door.The residual deformation can be recovered by the effect of ventilating negative pressure,which is favorable for reducing air leakage.The dynamic response characteristics and laws of explosion doors in the process of explosion venting are revealed,and key components and defects are discovered.Through continuous improvement and simulation verification,two mature typical design schemes of the new-type explosion doors are developed,called “Guiding-buffering type explosion door” and “Double-door type explosion door”.The research shows that the main restraining factors for explosion resisting performance of the guiding-buffering type explosion door are the bending stiffness of door body and the inertial of the guide mechanism.The explosion resisting performance of the double-door type explosion door depends on its key components including door-hinge,buffer walls and support frame.The technical characteristics of the double-door type explosion door include frame-type guide,umbrella-shaped buffering and limiting mechanism and disc-shaped door body.The structure features of double-door type explosion door includes buffer wall,flexure hinge and variable mass weight.The results of full-scale numerical simulations show that the principle and the structural design of the two new-type explosion doors are correct,the key functions such as self-resetting are reliable,and the bearable impact load is greater than the load with an overpressure of 300 kPa and a duration of 20 milliseconds.The work of this paper not only enriches and develops the protection method and theory against shock waves,but also enhance the research foundation for the scientific and technical issues of explosion doors.The study is of significance in developing the safety protection theory and technology of explosion doors for vertical shafts in coal mines.