Study Of Bridge Pier Impacted By Debris Flow

Debris flow is a common natural disaster in mountainous areas. Two-thirds of China’s total lands are mountainous areas. As one of the most serious national disasters, debris flow happens widely in China. With the development of our economic and transportation in mountainous areas, the chance that debris flow damages structures, such as road and rail bridges in culverts and other engineering facilities, is increasing. Thus the research of debris flow is attracting the world’s attention. Bridges as a key point of the road, once were destroyed, and the repair is more difficult than other parts of the road. Therefore, in order to reduce the impact of debris flow that effect on bridges, study on mechanism and control theory of debris flow damages pier area has got an important significance.This thesis describes the basic features of debris flow and a detailed study of debris flow impaction parameters, it discusses the physical model, mathematical model and turbulence model of debris flow simulation. Basic on this, the transient analysis of ANSYS simulate the impaction of large rocks of debris flow on piers, ANSYS Workbench implement fluid-structure interaction between mudslides and piers. Finally I gets the following conclusions:(1) Displacement of the pier is mainly produced by mudslides overall impact. When it is subjected to the impact of large stones, the displacement will increase by more than60%.(2)Periodic stress and displacement of pier are related to the density, speed, structure, stiffness of mudslides. If debris flow impacts the same pier, as the flow rate increasing, the maximum displacement of the pier increases.(3) When a pier is impacted by the debris flow, the bottom of the pier will yield a large tensile stress. If the bottom of the pier’s reinforcement is inadequate, the bottom of the pier would be destroyed. Meanwhile, part of the pier yield a large stress concentration, and it is caused by the impact of debris flow.(4)This paper simulates the dynamic characteristics and flow field numerical of debris flow by using CFX software, and then the flow field data, flow charts, and other pressure cloud of debris flow are obtained. They have value in the prevention and reference of landslides.(5)If consider the debris flow as a homogeneous body, the results of the impact force are approximately30%smaller than compared to specification.(6)The same cross-sectional area of the round end pier and rectangular-shaped pier in the same conditions that under the impact of debris flow, they are suffered from the same momentum. But stress concentration will be occurred in the bottom corner of the rectangular piers. The stress and displacement of the rectangular piers are also much larger than the ones of the round end pier. Therefore, round end piers should be used in the debris flow disaster-prone areas.