基于水文不确定性的桥梁全寿命周期冲刷易损性分析

Analysis of scour vulnerability for bridge lifetime based on hydrological uncertainty

摘要

【目的】冲刷坑形成是桥梁在洪水作用下水毁的主要原因。水文信息不确定性与多层土冲刷对冲刷深度预测的影响较大，需要评估桥梁全寿命周期内在洪水冲刷下的安全性能。【方法】以某实际桥梁工程为例，基于不完全的水文记录信息，采用季节性自回归积分滑动平均(SARIMA)模型对桥梁桩基全寿命周期内的冲刷深度进行统计分析。依据AASHTO规范，考虑桥梁桩基在洪水作用下的四种失效模式，构建了基于概率冲刷深度的时变安全性能评估模型，并获得全寿命周期内的时变易损性曲线。【结果】结果表明，所提出的方法能够有效预测桥梁基础冲刷深度与服役时间之间的关系，冲刷深度随时间先快速增长，后逐渐趋缓，前25 a增长较明显，之后减慢。【结论】桩基冲刷深度预测值随服役时间延长而增加，且其失效概率与埋深成负相关，但受土层参数的影响。该方法可为桥梁全寿命周期内的冲刷评估和设计提供理论依据，提升桥梁在洪水作用下的安全性。

Abstract

[Objective] The formation of scour holes is a primary cause of bridge failure under flood conditions. Uncertainty in hydrological data and multi-layer soil erosion significantly impact the accuracy of scour depth predictions. Evaluating the safety performance of bridges over their entire lifecycle under flood-induced scour is essential. [Methods] Using a real bridge project as a case study, the Seasonal Autoregressive Integrated Moving Average(SARIMA) model was applied to conduct a statistical analysis of scour depth over the bridge's lifecycle, based on incomplete hydrological data. Following AASHTO guidelines, four failure modes of bridge pile foundations under flood conditions were considered, and a time-dependent safety performance evaluation model based on probabilistic scour depth was developed. The time-dependent vulnerability curves for the bridge's lifecycle were also obtained. [Results] The result demonstrated that the proposed method effectively predicts the relationship between bridge foundation scour depth and service time, with scour depth initially increasing rapidly before gradually slowing down, particularly over the first 25 years. [Conclusion] The predicted pile foundation scour depth increases with extended service time, and its failure probability is negatively correlated with embedment depth, but is influenced by soil layer parameters. This method provides a theoretical basis for assessing and designing bridge scour over its lifecycle, improving bridge safety under flood conditions.

关键词

桥梁基础 / 风险评估 / 水文信息 / 冲刷深度 / 易损性 / 影响因素

Key words

bridge foundation / risk assessment / hydrological information / scour depth / vulnerability / influencing factor

基金资助

国家自然科学基金项目(52378135)

国家自然科学基金项目(52022021)

国家自然科学基金项目(51978160)