Flume Experiment Study On Slope Angle Of Granular Sand Accumulation Under The Influence Of Water Flow

The granular sand accumulation is widely found in nature,such as dyke dam?sandbar or bottomland composed of granular sand,etc.And these accumulations will be all or partly in the water flow environments.Under the influence of water flow,the accumulations experience deformation,collapse,and ultimately form a stable form.Collapses of these granular sand accumulations are complicated and volatile due to different flow conditions or sediment particle sizes.It is of great significance to study the variation laws of lateral stabilized slope angle,the stability of dyke dam and bank slope formed by the accumulation of granular particles.This paper uses the theory of soil mechanics,sediment mechanics and other disciplines theory.Combining mathematical model calculation with flume experiment,we observe the morphological changes of the granular sand accumulation under the influence of water flow,including the flow field structure around the granular sand accumulation,the variation of the slope shape and the formula of the dynamic repose angle under the action of water flow.The main research results are as follows:The higher the inlet flow velocity is,the greater of the vertical flow velocity of the front flow surface,the backflow surface,the lateral flow surface and the top.And the average velocity increase in the vertical velocity of each slope.Under the same flow condition,the flow intensity of the slope from the highest to the lowest is in the top of the accumulation body,the lateral flow surface,the front flow surface and the backflow surface.The flow of water flowing through the granular sand accumulation has a significant three-dimensional and non-uniformity,and the effects of water flow on the sediment particles in different orientations are different.For the front flow surface,the greater the inlet flow,the greater the effect of the flow on the slope,and the greater the effect of the flow on the slope as the slope increases.For the lateral flow surface,the greater the inlet flow,the effects of water on the slope for greater the intensity,but the amplitude is more gentle than the incident flow surface.With the increase of the slope elevation,the effect of the flow on the slope is greater,but the variation is more uniform than the incident flow surface.The backflow surface is a masking area where the flow intensity is very weak on the surface,and the area scale is reduced with the increase of the inlet flow rate.The granular sand accumulation under the action of water flow will be unstable with varying degrees of adjustments and evolutions.In terms of slope stability,the backflow surface is the most stable,followed by the lateral flow surface,the weakest incident flow surface.The front flow surface is scoured under the influence of water flow,and the slope angle gradually becomes slow.Lateral flow surface will present the upper scour,lower accumulation.Sediment accumulation from incident flow surface and scouring of bottom sediment combination makes the surface of the lateral flow surface to achieve dynamic balance and form a stable slope angle.Back flow surface slope is very stable,and its stable slope angle is close to the hydrostatic angle of repose.The main factors affecting the slope angle are flow velocity and particle sizes.The greater the flow intensity under the same particle size,the smaller the stable slope angle and the higher the sensitivity of the stable slope angle to the change of the flow velocity.The larger the particle size of the sand particles in the same flow condition,the greater the stability slope angle and the lower the sensitivity of the stable slope angle to the change of the flow rate.In addition,based on the force analysis of sand on the slope in lateral flow environment and the introduction of relative velocity conception,dynamic repose angle calculation formula of the uniform non-cohesive sand under influence of lateral flow is established.