洪水致弯曲河道挡墙稳定性衰变

Stability attenuation of retaining wall under flood in river bend

天然河道蜿蜒曲折,河湾处环流助长紊动、引发凹岸淘蚀冲刷,导致沿河公路挡墙水毁频发。针对弯道水流运动规律,对洪水条件下弯道挡墙进行受力分析;基于挡墙稳定性分析力学模型,推导了弯曲河道挡墙稳定系数计算公式,给出挡墙基底极限冲深计算方程。通过算例验证了在河湾平缓条件下弯道洪水冲击计算的合理性,并对挡墙稳定性衰减影响因素进行分析。结果表明:洪水上涨时,在墙底未发生冲刷条件下,随着弯道处洪水对挡墙的冲击荷载增大,挡墙稳定性提高;在墙底发生冲刷条件下,挡墙稳定性降低,墙底淘蚀可能导致挡墙倾覆失稳。洪水陡落时,挡墙稳定性随挡墙前后水位差增大而降低,挡墙的抗滑稳定系数衰减速度比抗倾覆稳定系数衰减速度更快,挡墙滑移失稳可能性较大。得出的挡墙稳定系数计算方法的结果与现场情况基本吻合,可为类似沿河挡墙的设计与研究提供理论参考。

Natural rivers are curved. Bend circulation contributes to turbulence and causes erosion in concave bank, resulting in frequent flood damage on retaining wall along the river-side road. To investigate the trend of water movement at the river bend, force of retaining wall was analyzed in the condition of the flood. Based on the mechanical model of stability analysis of retaining wall, the calculating formula of the bend river retaining wall stability coefficient was deduced and calculation equation of limit punching depth under the wall was given. Shock calculation of rationality was verified in the gentle bend flood conditions and the stability of wall attenuation factors was analyzed by a numerical example. The results show that the impact load on the wall increases and the stability of wall is improved in the period of flood level rising and no erosion occurrence. However, the stability of retaining wall decreases when erosion occurs, and wall bottom scour may lead to overturning. The stability of wall decreases with the increase of water level difference between the front and back of the retaining wall, and the anti-sliding stability coefficient of the wall attenuates faster than that of the anti-overturning stability coefficient. The instability possibility of the wall is relatively high in the period of flood steeping. The calculation method and results of retaining stability coefficient are consistent with the site conditions, providing a theoretical reference for similar design and research of retaining walls along rivers.