高速远程滑坡超前冲击气浪三维动力学分析

为研究沟谷多级折射高速远程滑坡超前冲击气浪的特征,以牛圈沟滑坡三维地形形态为原型,采用CFD软件,引入Voellmy准则定义运动阻力,在反演碎屑流运动全过程的同时,对其冲击气浪的流场特征进行了数值模拟,分析其形成的动力学机制。结果表明:(1)牛圈沟滑坡从启动到停止历时为119 s,最大速度出现在滑体内部靠近前缘处,峰值分别为14 s的52 m/s、27 s的55 m/s和50 s的49 m/s。(2)气浪速度的最大值50 s时为38 m/s,其压强的最大值达657 Pa,相当于11级暴风。(3)当碎屑流前方出现高大的障壁时,来不及扩散的高压气流产生极为明显的压强梯度;当其前方遇跌坎或翻越山脊冲向山坡下方在其速度瞬间增大的同时,强烈压缩前方空气并导致其压强值局部出现陡增。

Three-dimensional modelling and dynamic analysis of the airblast generated by rock avalanche

In order to study the intensity and the variation law of the airblast induced during the high-speed motion of rock avalanche with multiple angle changes along its travelling path, a true three-dimensional model of the Niujuangou rock avalanche is studied with the software CFD by introducing the definition of resistance along traveling path under the law of Voellmy. The characteristic of the airblast flow field is simulated emphatically with the dynamic mechanism of the airblast discussed based on the back-analysis of the whole travelling process of the Niujuangou rock avalanche. The results show: (1) The whole travelling process of the sliding mass lasts 119 s, and the maximum speed at every moment appears in the part near the front zone of the sliding mass (except t=50 s, the maximum speed appears in the front zone of the sliding mass) with three ultimate values of 52 m/s at 14th second, 55 m/s at 27 th second, and 49 m/s at 50 th second, respectively. (2) The maximum velocity of the airblast appears at the 50th second with its value reaching 38 m/s. The maximum pressure of the airblast, 657 Pa, is generated at the moment the sliding mass bursts out the scarp, which is equivalent to the violent storm. The squeezing effect of the sliding mass on the air ahead is the most obvious when the sliding mass is moving fast and the leading height is higher. (3) The topography along the sliding path displays a large influence on the distribution of airblast pressure. During the high-speed motion of the sliding mass, an obvious gradient variation of air pressure is induced when an obstruction appears along its sliding path, resulting in a destructive effect. When the sliding mass rushes down a scarp or ridge, the velocity of sliding mass will increase rapidly with a negative pressure generated inside of the sliding mass because of weightlessness, meanwhile, a sharply increase of the air pressure will also appear at some locations distributed ahead of the sliding mass due to the intensive compression induced by the sliding mass.