Dust Lifting Process Induced By Flowfield Before Shock Wave And Its Multiphase Destructive Effects

Gas explosion in underground coal mines has been the most significant disaster in most mining countries. It not only directly causes substantial property damage and human casualties, but also can induce secondary disasters. The multi-phase destructive effect coupling gas explosion shock wave and high-speed dust particles which was induced by dust lifting behind shock wave was studied in this paper by more than 30 experiments, 50 numerical simulations and theoretical analysis integrating explosion, chemical reaction kinetics, multiphase fluid mechanics, material mechanics, rock mechanics, and other subjects. The occurrence of this kind of disasters and its key scientific issues were discussed. The main innovative achievements made are as follows:Gas explosion Chemistry and Physics in comfined mine network were discussed in detail. The relationship between dynamic pressure, reflected shock wave pressure and explosion overpressure was established. The effect of connetion type of tunnels on explosion propagation was studied for the first time. It was found that peak overpressure in parallel tunnels was higher that in normal ones. The flow field before shock wave and other parameters during explosion propagation were obtained by numerical simulations. The relationship between peak gas velocity and peak overpressure followed linear function. They were fitted well by equation: u_gas=3573.9-12228.8△P_max in the initial stage of explosion and by equation: u_gas=235.6+1510.1△P_max in the fininal stage. The shock wave oscillation obviously in confined tunnels was observed, which was induced by the relection of FCW and FSW. Oscillation of shock wave has lead to higer peak overpressure. Oscillation pectrogram plot of reflection wave and its relationship with arrival time was given by us for the first time. The correlation of first peak overpressure and peak gas velocity was suggested for the prediction of dust lifting beford shock wave.The E-E model was used to study the dust lifting process before shock wave. The dust lifting process obtained by this method was fitted well with experimental results by other researchers. The effect of gas velocity on dust lifting process was studied. It was found that the best results didn't appear at highest gas velocity. The best dust lifting process was at the initial stage of gas explosion, whose gas velocity lies between 100 and 300m/s (corresponding peak overpressure was less than 0.3MPa). A study on the effect of dust density on dust lifting found that dust density contributed less, but the dust diameter play an important role in dust lifting.The multi-phase destructive effect coupling gas explosion shock wave and high-speed dust particles which was induced by dust lifting behind shock wave was studied for the first time. The stress distribution in materials under shock wave and method for calculating stress, σsolid, caused by high-speed particals were described. Experimental apparatus was established to study the multiphase destructive effects. The comparision of destroy by gas explosion shock wave and multiphase destructive effects shows that the materials was destroyed more seriously because of the addinitional stress of high-speed particals.Present research findings might have important scientific and applicational significance for the prevention of multi-phase destructive effect coupling gas explosion shock wave and high-speed dust particles.In addition, 14 papers about research results were and will be published, in which one has been indexed by EI, four will be published in EI source journals, one will be indexed by EI in a conference paper and two have been submitted to SCI journals.There are 71 figures, 12 tables and 165 references in this thesis.