中国古代桥梁冲刷防护策略的典型案例与特征分析

Typical Cases and Characteristics of Scour Countermeasures of Ancient Chinese Bridges

摘要:

我国古代桥梁工程历史悠久、底蕴深厚，是各地历史风貌和地域文化的重要载体。然而，长期服役状态和自然条件演化导致现存古桥性能衰减，特别是近年来气候变化加剧，古桥损毁案例频发，古桥的保护迫在眉睫。统计资料显示，在古代桥梁服役期间，冲刷是限制其使用寿命的重要因素，对桥梁基础和整体结构的长期危害不容忽视。现存古桥在其建设时期，根据不同的水文及地质条件，结合对冲刷现象的定性认识，提出并运用了一些防护措施。选取了三个代表性现存古桥案例，分析了其采用的分水尖、抛石基础和排桩等防护措施，结合目前的冲刷发生与演化的判断准则，分析其作用机理与防护效益。进一步从御灾种类、适用范围和服役性能三方面因素提出保护效益指数，并通过服役性能指数完善了冲刷演化判断模型，对古代桥梁的保护修缮工作提供一定的建议。

关键词:古代桥梁工程;基础冲刷;水毁防护;保护效益指数;保护开发

Abstract:

Chinese ancient bridge engineering has a long and abundant history， and can well reflect historical features and regional culture of China. However， the performance of the existing ancient bridges has been degraded because of the long-term service and the evolution of natural environment. Especially in recent years， with the intensification of climate change， more ancient bridges have been being damaged， which makes the relevant protection in urgent need. Statistics show that scour causes long-term adverse effect to the foundation and wholistic structure， limiting the service life of ancient bridges. During ancient times， based on the qualitative understanding of the scour， some countermeasures were created and applied， according to the different hydrological and geological conditions. In this paper， combined with the present criteria for the occurrence and development of scour， the mechanism and protection benefit of countermeasures， such as cutwaters， riprap-foundations and pilings， which were adopted by three representative existing ancient bridges， are analyzed. Furthermore， the protection effect index is proposed from three aspects including disaster types， the application scope and the service performance. Besides， the criterion is improved by service performance index， based on which some suggestions are provided for the protection and repair work of ancient bridges.

Key words:ancient bridges;scour around foundations;countermeasures;protection effect index;protection and development