桥墩基础施工河床局部冲刷研究

Experimental study on local scour of bridge pier foundation in construction duration

天然河流中水流受到建筑物的阻碍时,产生紊动涡旋,局部河床泥沙在水流紊动剪应力作用下起动,并被涡旋流带向下游,建筑物局部河床因此受到侵蚀而下降,形成局部冲刷坑。跨河大桥桥墩的局部冲刷就是如此。桥墩及其基础与水深或河床的相对位置影响着局部冲刷深度的发展。本文通过室内试验研究了桥墩下部钢围堰基础施工的相对高程对河床局部冲刷最大深度的影响,探讨了工后钢围堰顶部处于相对水深的不同高度时局部冲刷发展的规律,并将这些影响因素用墩形系数法计入局部冲刷深度计算中,给出了计算公式。本文的研究对目前跨江及跨海大尺度桥墩基础工程施工具有指导意义。

Turbulent horse-shoe vortex occurs when flow in alluvial river meets obstructions, such as bridge piers and their foundations. Local sediments in bed suspend and move with flow due to effects of the turbulent shear stress. Sand bed is eroded around bridge piers. The location of the piers and their foundations into the flow affects the local scour depth. In this paper laboratory experiments have been conducted for studying the scour maximum depth in the case of construction of bridge foundations. The variations of scour depth with the location of the foundation have been investigated and a technique of pier shape coefficient for calculating scour depth has been forwarded. The results of this paper have significant values in construction of bridges with large-scale foundations.