Study On Mechanism Of Airblast Generated By Niujuangou Rock Avalanche

During the rapid motion of rock avalanche with multiple angle changes along its travelling path, there existed multi-deflected impact with the both sides of the valley. Debris-flow compresses the air in the valley and generates destructive airblast in the front and on both sides of its motion path. Recent years, along with the rapid development of computation technology, numerical simulation is extensively used in the research of rock avalanche. In this thesis using FLUENT solver for computational fluid dynamics and introducing the law of Voellmy, the author fulfilled the numerical simulation of dynamics of airblast induced by the moving process of the Niujuangou rock avalanche. The main results can be summarized as follows:(1)Niuquangou rock avalanche from start to pile up lasts119s, the total long run-out is2.9kilometers and the maximum velocity is55m/s. The maximum velocity at every moment appears in the part near the front zone of the sliding mass (except t=50s, the maximum velocity appears in the front zone of the sliding mass) during the movement of debris-flow, and the difference in speed between the leading and trailing edges of it is significant.(2)The maximum velocity of the airblast appears at the50th seconds with its value reached38m/s. There are two peaks in the value of airblast pressure, the one value is in the start of it is591Pa, the other is formed while the debris mass entered into Niuquangou and is657Pa. The destroy power caused by airblast equivalent to one of wind power of the11th grade. Along the sliding direction, the airblast pressure decrease with the greater distance away from the leading edges of debris mass.(3)The terrain of valley has significant impact on the pressure generated by debris-flow. The pressure of airblast can be markedly increased when a steep wall appears in front of debris-flow mass and/or when the cross section of valley becomes narrow.