An Elementary Study for the Mechanism of Earth Dam Break

摘要

Based on the force balance fundamental of sand grain, it was analyzed that the force condition of the grain start velocity in water flow erosion as earth dam breaking process. Expressions of a rolling and a suspending start velocity of grain were deduced from that analysis. The relationships between grain start velocity and the grain diameter, flow direction, shear strength parameters were studied respectively, which were illustrated as curves. It was made known that there were different manners of grain start moving because of the sand grain diameter from small to large. If the grain diameter was smaller than 4. 0cm, grains start moving as suspending manner. And other vice, grains might roll in water flow erosion happening. The suspending start velocity was not affected by the shear strength parameters, but the rolling start velocity was augmenting with the shear strength parameters go large as a nonlinear curve manner. The slope gradient could have a decisive action to force direction of grains. The larger the gradient, the easier the grains start moving. And rolling might be the start moving manner.