高压水射流侵彻混凝土致裂形态控制机理与弱作用区损伤劣化特征研究

High pressure water jet technology has a broad prospect in concrete structure maintenance and emergency demolition. However, it still has some disadvantages, such as high threshold pump pressure, larger energy consumption and lack of controllability of crack. In order to solve these problems, it needs to find the mechanism of crack forms control and damage of high pressure water jet penetrating concrete. Theoretical analysis, experimental tests, numerical simulation, optimization technologies are carried out in this project. It establishes the relations among strain field, displacement field distribution characteristics and crack propagation forms, analyzes the crack dynamic starting criteria by water-hammer effect and crack propagation rule under stress wave, and studies the influence mechanism of stress wave spectrum characteristics on crack propagation. Then the fluctuation cycle, propagation speed, attenuation rule and other dynamic response characteristics of stress wave under water jet are researched, and a microscopic damage numerical model of high pressure water jet penetrating concrete is built, to reveal the damage mechanism of concrete under water jet. And it also studies the damage distribution and degradation characteristics in weak-effect zone of concrete penetrated by high pressure water jet, explores the sensitivity of water jet parameters to damaging concrete, and presents a damage prediction model of high pressure water jet penetrating concrete, with multiple parameters. The results will promote high pressure water jet breaking concrete technology, and they have important scientific significance and practical value to concrete structure maintenance and emergency demolition.

高压水射流技术在混凝土结构养护维修、应急破拆中具有广阔应用前景。但高压水射流破除混凝土技术存在门槛泵压高，比能耗大，致裂可控性仍显不足等问题，这需对射流侵彻混凝土形态控制及损伤机理等进行研究。本项目结合试验测试、理论分析、数值模拟及优化技术，拟开展以下研究：①研究射流侵彻混凝土应变场、位移场分布特征与裂纹扩展形态之间关系，分析水锤效应下裂纹动态起始判据和应力波作用下裂纹传播规则，揭示应力波频谱特征对裂纹扩展形态影响机制。②研究射流侵彻下混凝土内部应力波波动周期、传播速度、衰减规律等动力响应特性，构建射流侵彻混凝土细观损伤数值模型，阐释射流致损混凝土力学机理。③研究射流弱作用区混凝土损伤分布规律及劣化特征，考察射流参数对混凝土的致损敏感性，建立基于多射流参数的高压水射流侵彻混凝土损伤预测模型。研究结果对促进射流破除混凝土技术发展，提高混凝土结构修复、救援破拆水平，具有重要科学意义和实用价值。

高压水射流破除混凝土技术在质量、安全、环保等方面存在诸多优势，可在混凝土结构维修、应急拆除等工程中发挥重要作用。但高压水射流破碎混凝土作用机理尚不明晰，限制了该技术的进一步拓展。鉴于此，本项目围绕高压水射流破除混凝土技术，重点开展了一系列关于高压水射流侵彻混凝土致裂及损伤机理的基础研究。主要研究成果如下：.（1）本项目综合了高速摄像技术、无损检测技术、图像处理技术及非接触式全场应变测试技术等多种研究方法，研究了高压水射流冲击下混凝土内、外部破碎及致裂物理力学过程，阐释了混凝土“启裂-扩展-溃裂”不同破坏阶段的致裂机理，基于图像灰度值的损伤表征方法，揭示了高压水射流冲击混凝土内部CT尺度损伤分布特征，定量指出射流强冲击作用会在混凝土未破碎区的骨料与砂浆基体过渡区形成损伤。.（2）结合相似材料、模型试验及高速摄像技术，构建了高压水射流冲击透明类混凝土冲蚀孔洞及裂纹扩展检测系统，可视化研究了射流冲击下混凝土水锤压缩区扩展、非压缩区扩展及侵彻贯通后扩展的典型过程，揭示了高压水射流冲蚀混凝土破碎区演进特征及裂纹扩展规律，并从理论上提出了冲蚀孔洞演进的临界判据。.（3）考虑高压水射流作用下混凝土的高应变率、大变形特点，以及流固耦合等问题，构建基于FEM-SPH耦合的高压水射流冲击混凝土数值模型，研究了混凝土在高压水射流冲击作用下裂纹萌生、扩展及失效演化过程，揭示了高压水射流冲击下混凝土内部应力波传播规律。. 研究结果对提高高压水射流破除混凝土技术应用水平，提升我国混凝土结构修复水平和事故应急破拆能力等，具有重要的理论意义和工程价值。