两相泥石流龙头的非恒定运动过程及能量特征

两相泥石流通常会出现高陡的龙头,其集中了大量的粗大卵石和砾石,呈现间歇性或波动性的运动。两相泥石流的运动除了取决于流体本身的流变特征外,液相和固相之间的能量传递也起到了重要作用,利用能量分析方法来研究两相泥石流固相、液相和龙头之间的能量转化机理是研究两相泥石流非恒定运动的有效途径。通过野外两相泥石流原型和水槽实验,研究其非恒定运动过程,结果表明,两相泥石流的龙头在泥石流起动初始阶段逐渐增长,当运动到一段距离后,趋于稳定。龙头高度和速度都有波动特征,通过能量分析建立了物理方程,分析证明两相泥石流龙头运动的平均速度正比于沟道的坡降和激发泥石流的洪水流量,反比于龙头的体积。

Mechanism of the intermittent motion of two-phase debris flows head and the energy character

A typical two-phase debris flow exhibits a high and steep flow head consisting of rolling boulders and cobbles and intermittent or fluctuating moving velocity. The relative motion between the solid phase and the liquid phase is obvious. The motion of a two-phase debris flow depends on not only the rheological properties of the flow,but also the energy transmission between the solid and liquid phases. In addition to the rheological characteristics of two-phase debris flow, energy transfer between liquid phase and solid phase plays an important role. Energy analysis method was used to study the energy transfer mechanism between the two phase flows and simulate the motion of two-phase flow. This paper analyzed the intermittent feature of two-phase debris flows based on videos of field debris flows and flume experiments. The experiments showed that the height of the head of the two-phase debris flow increased gradually at the initiation stage and reached equilibrium at a certain distance. The height growth and the velocity of the flow head showed fluctuating characteristics. Physical equations were established and the analyses proved that the average velocity of the two-phase debris flow head was proportional to the gully slope and flood discharge, and inversely proportional to the volume of the debris flow head.