清淤对软土地基古石桥地基变形的影响及机制研究

Influence of dredging on the foundation deformation of antique stone bridge built on soft ground and its mechanistic analysis

在当今城市景观提质改造活动积极开展的背景之下,滨水或水域古建筑多面临着清淤的现实需求。为有效保护古建筑,需要充分考虑清淤对古建筑地基变形的影响。以某软土地基古石桥为例,建立了桥体与场地地基土层的三维模型,研究了清淤深度、清淤坡肩宽度和清淤坡比3个参数对软土地基古石桥位移和应力分布的影响规律,并进一步分析了清淤对古石桥地基变形影响的机制。研究结果表明:(1)清淤开挖效应主要表现为引起桥体及邻近区的土体位移、改变应力分布和导致邻近区土体出现塑性区3个方面,使得古桥自身及其邻近区土体处于更为复杂的应力场与位移场之中;(2)不同清淤参数对古桥及其邻近区地层位移场和应力场的影响以及影响程度存在差别,清淤深度主要影响土体的位移变化幅度,清淤坡肩宽度控制着清淤效应的波及范围,清淤坡比和清淤坡肩宽度共同影响着土体位移曲线形态的变化和塑性区的发展;(3)在实际清淤工作中,清淤参数的设置除了需要满足工程可行性与经济性的要求之外,还应当合理确定清淤参数、控制清淤开挖对相邻古建筑的影响程度,在确定设计清淤深度时需要综合考虑清淤坡肩宽度和清淤坡比。研究成果对古建筑的清淤工作有实际指导意义。

[Objective]The great demand for urban landscape improvement and reconstruction has required increasing dredging practices for waterfront buildings,particularly antique buildings.To effectively protect such antique buildings,the influence of dredging on the ground deformation of antique buildings needs to be carefully considered in the dredging operations.[Methods]To obtain a better understanding of the effect of dredging activities on antique buildings,the influence of dredging depth,dredging slope shoulder width and dredging slope ratio on the displacement and stress distribution of an antique stone bridge on soft ground via a three-dimensional model of the bridge body and its ground strata was studied in this paper.Based on the calculated results,mechanistic explanations of dredging on the ground deformation of antique stone bridges were proposed.[Results]The simulated results show the following:①Dredging effects on the antique stone bridge mainly appeared as giving rise to the displacement of the bridge and the near strata,changing the stress distribution,and forming a plastic zone in the adjacent area of strata.As a result,dredging activities render a more complex stress and displacement distribution to the bridge and the strata around the bridge.②Different dredging parameters have different effects on the displacement fields and stress fields of the bridge and its surrounding area.The dredging depth primarily affects the displacement magnitude of the soil,and the dredging slope shoulder width is the crucial factor affecting the scope of the dredging effect,whereas the dredging slope ratio and the dredging slope shoulder width jointly manipulate the change in the soil displacement curve and the development of the plastic zone.③In dredging projects,the setting of dredging parameters should not only meet the requirements of engineering practicability and economy but also reasonably determine the dredging parameters and control the impact of dredging on adjacent ancient buildings and take into account the width of the dredging slope shoulder width and the dredging slope ratio when determining the designed dredging depth.[Conclusion]The results in this work are of practical significance for dredging activity in antique building protection.