Through the detailed investigation of the occurrence,development and accumulation process of WA gully debris flow in south slope of Qinling Mountains Jiuqiancha gully in September 19th,2014,and analysis the particle size distribution and bulk density of matter source,the velocity,flow rate and the maximum duration of debris flow and other physical properties and dynamic characteristics when the debris flow occurs,that WA gully debris flow formation process has clearly burst effect,and antecedent precipitation had significant effects on forma tion of debris flow.The WA gully is a viscous mining dregs debris flow with high velocity,large flow,long duration,which is affected by precipitation.Motor process of WA gully debris flow has the feature of high throwaway,carry the material along the bottom of gully,blocked climbing,bypass flow turning,curve speed up and go forward with s-type.The WA gully debris flow hazard mode was strictly affected by the path in the accumulation of debris,especially the high alluvial that carried tremendous energy when falling in the bend of s-type curve,which is the main cause of this disaster.%通过详细调查2014年9月19日秦岭南坡九千岔沟的洼沟泥石流的发生、发展和堆积过程,分析泥石流发生时物源的颗粒级配、容重及泥石流的流速、流量、最大历时等物理性质和动力学特征,认为洼沟泥石流形成过程具有明显的溃决效应,且前期降水对该泥石流的形成有显著影响;洼沟泥石流是一种流速高、流量大、历时长的粘性、降水弃渣型泥石流;洼沟泥石流运动过程具有高位远抛、沿沟揭底、受阻爬坡、分流折转、弯道加速、S型前进的特点;洼沟泥石流致灾模式严格受泥石流堆积过程中行进路线的影响,尤其是高位冲积,在S型弧线弯道处跌落时能量巨大,是本次致灾的主要原因.
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