Study On The Scour Mechanism Of Protective Construction Induced By Unsteady Flow

In western regions, highway is always located along rivers, and the roadbed is seriously scoured by water flow. Influenced by many kinds of factors of geology, hydrology, climate, water destroy mechanism and protection technology seem complicated. The problem is studied through many experiments and based on the S&T projects of traffic construction in China's West,"Study on Disease Control and Ecological Environmental Protection in G315"-"Study on the Water Destroy Controlled from Mangya to Qiemo in G315"(No.2001 318 365 91) in this paper.Based on brief and commentary on local flow field around roadbed along river, scour mechanism and simulation, sediment motion characteristics in mountain rivers are analyzed, and the study on incipient mechanism and incipient velocity of uniform sediment on reunite slope is discussed. At the same time, Pulsating characteristic of turbulence is studied and Pulsating range of velocity with the Fr and Re is derived. Local flow condition, scour types, scour mechanism and factors influencing the scour depth are analyzed. Experiment study about water scour is undertaken, and scour depth with different factors about water discharge, flow depth, velocity, sediment ,different Angle and Protective materials and pattern of protecting is studied.。In the paper, a computing method of velocity for reunite slope is discussed, which considers the slope characteristics and draw the relation of incipient velocity on the reunite slope with the incipient velocity on slight slope. Through the method of theoretical analysis and experiment study, the formula of the maximum scour depth and scour width of prevention wall in concave bank is put forward. The method of dimensional theory and regression analysis is used to deprive the formula for calculating the maximum scour depth. In order to satisfy with erosion protection of G315 road construction, 4 new protective structures are studied in model test, such as sand-bag pillow, geo-grade cage filled in sand, box assembled with zinc-plating steel wire bundled plastic and filled in gravel. The formulation of the maximum scour depth and scour width for prevention structure is revised.