Abstract: Due to the perennial erosion of the substructure foundation in complex aquatic environments and the potential impact of drifting objects, wading bridges are prone to developing apparent defects. Therefore, it is essential to conduct regular inspections to assess their safety status. Owing to the limitations of underwater scenarios, conventional damage detection methods are difficult to achieve effective detection of damage. To address this issue, 3D sonar measurement technology was employed for the inspection of underwater foundations of bridges. The basic principles of 3D sonar measurement technology and its basic implementation process for underwater foundations of bridges were introduced, and an integrated processing method covering point-cloud acquisition, data processing and foundation morphology extraction was proposed, so as to generate a three-dimensional point-cloud model that could accurately reflect the apparent characteristics of the foundation. The results indicate that, under complex underwater environmental conditions, the proposed method can effectively achieve three-dimensional shape reconstruction and dimensional measurement for different types of foundations. For large-scale underwater foundations such as caissons and cofferdams, the maximum measurement error is only 7.9%, demonstrating good detection accuracy and engineering applicability. For small-scale components such as pile groups, although the average diameter measurement error reaches 18.2% due to weaker echo signals and sparse point clouds, the proposed method can still satisfy the basic requirements for geometric feature identification and safety assessment of the foundations.

Key words: bridge engineering; underwater inspection; 3D sonar; point cloud; data processing

摘要： 涉水桥梁下部基础在常年的复杂水环境侵蚀以及潜在漂流物碰撞下易产生表观缺陷，因此，定期检测以掌握其安全状况十分必要。受水下场景的限制，常规的损伤检测手段难以实现对损伤的有效探测，为此，利用3D声呐测量技术开展对桥梁水下基础的检测。基于3D声呐测量技术的基本原理以及其在桥梁水下基础的基本实施流程，提出了集点云获取、数据处理以及基础形态提取的完整处理方法，生成了能够精确反映基础表观特征的三维点云模型。结果表明：在复杂水下环境条件下，笔者方法能够较好地实现不同类型基础的三维形态重建与尺寸量测；对于沉井、围堰等尺度较大的水下基础，其最大测量误差仅为7.9%，显示出较好的检测精度与工程适用性；对于群桩等小尺度构件，虽然受回波信息较弱和点云稀疏等因素影响，平均直径测量误差为18.2%，但仍可满足基础几何特征识别与安全评估的基本需求。

关键词: 桥梁工程； 水下检测； 3D声呐； 点云； 数据处理