泥石流的运动机理和减阻

野外调查研究发现,存在着两种具有不同动力学特征和机理的泥石流,粘滞性泥石流和两相泥石流,粘滞性泥石流由卵石、沙和粘土构成,难以区分固相和液相,为典型的非牛顿体,具有间歇性流动,“铺床现象”,高达60％的减阻和显著超高等流动特点,粘滞性泥石流的阻力远小于流变参数所代表的阻力,传统的利用本构方程研究阻力的方法不能解决问题,研究表明,其30％的减阻是由于铺床作用,另外20％－30％,是由于流动混合物充气所致,两相泥石流主要由粗颗粒物质构成,两相之间有明显的相对流动,显示较大的阻力和发生“石街”现象。粘滞性泥石流沟谷的中值坡度为0．16,两相泥石流阻力大,因而河谷的平均坡度较大（0．19－0．27）。

The mechanism of debris flow and drag reduction

Field inveStigations reveal that the resistance of debris now can not be approached byusing the constitative equations because the viscosity and other rheologic parameters represent much greatal resistance than the real debris flow. There are two types of debris now, namely viscous debris flow and tWO--phase debris flow. Viscous debris flow consistS of clay, silt, sand and gravel, and it is non--Newtonian, pseudo--one phase flow. It exhibitS "paving way process', drag nduCtion and extremely high super--elevation. The main flow is laAnnar, intondttent or wavy. The study 'indicates that the drag reduction is due tO the paving way process(30%) and air entrain~ (20% ~30%). The two--phase debris now consistS of gravel and boulders and exhibits obvious relative moment betWeen the solid phase and the liquid phase. So called "stone street# is fonned by the deposit. The slope of viscous debris flow gullies is smaller than that of two--phase debris flow gullies because of the drag reduction of the fO~r and higher resistance of the later.