竖向荷载下钢筋混凝土排水管道结构损伤声发射特征分析

Analysis of Acoustic Emission for Structural Damage Identification of Reinforced Concrete Drainage Pipes under Vertical Load

外压荷载是导致钢筋混凝土排水管道结构破坏和失效的重要原因之一,会造成管道破裂、泄漏、甚至路面坍塌。为了有效地表征钢筋混凝土排水管道在外压荷载作用下的损伤特性,采用声发射技术监测钢筋混凝土排水管道在竖向荷载作用下的损伤过程。根据管道加载过程中声发射能量的变化和积累,将管道的损伤阶段分为弹性压缩阶段、塑性破坏阶段和剩余强度阶段。在弹性压缩阶段,由于试样内部发生的破坏活动较少,声发射活动呈现较低水平;在塑性破坏阶段,声发射能量呈现出逐渐递增的趋势;在剩余强度阶段,当达到破坏荷载时,声发射能量和累积声发射能量曲线迅速上升,在管道严重开裂后,声发射能量逐渐下降。根据足尺管件加载破坏过程的声发射特性,提出了基于声发射信号的钢筋混凝土排水管道损伤识别评价指标:声发射能量(E)、累积声发射能量(∑E)以及加载过程中AF/RA(平均频率/上升角)值。该研究对于揭示钢筋混凝土排水管道结构在外压荷载下的损伤失效机理,建立科学的城市排水管道服役安全评价体系,提升排水管道病害治理水平具有重要意义。

External loading is one of the critical causes of structural damage and failure of reinforced concrete drainage pipes, which lead pipe failure, leakage and even road collapse. In order to effectively characterize the damage, the damage process of reinforced concrete drainage pipes under vertical load was monitored by acoustic emission technique in this study. According to the change and accumulation of acoustic emission energy during the pipe loading, the pipe’s damage stages were divided into the elastic compression stage, plastic damage stage, and residual strength stage. During the elastic compression stage, the acoustic emission activity presents a lower level due to the less damage activity occurring inside the specimen. During the plastic damage stage, the acoustic emission energy shows a gradual upward trend. During the residual strength stage, the acoustic emission energy and cumulative energy curves rise rapidly when the damage load is reached. The acoustic emission energy decreases gradually after the pipe severely cracked. Based on the acoustic emission characteristics during the full-scale pipes’ damage process, the evaluation indexes for damage identification of reinforced concrete drainage pipes by acoustic emission signals are proposed: acoustic emission energy(E) and accumulated acoustic emission energy (∑E) as well as average frequency/rise angle ratio(AF/RA) during the loading process. This study is essential for revealing the structure failure mechanism of reinforced concrete drainage pipes under external pressure, establishing a scientific evaluation system of urban drainage pipe service safety, and improving the pipe disease management capacity.