混凝土轴压受载声发射特征及失稳演化过程研究

Study on Acoustic Emission Characteristics and Instability Evolution Processes of Concrete Under Axial Compression

桥梁桩基混凝土承受轴向压载过大,其内部破坏开裂过程会释放弹性波,为量化压载失稳演化过程特征,通过现场原位钻取桥梁桩基结构芯样,采用轴向压载与声发射同步监测试验,研究混凝土试件加载全过程声发射时空演化特征,分析混凝土材料压载失稳破坏全过程与声发射振铃计数、能量释放、震源定位等表征参数的演化关系,获得加载过程与声发射特征关联性的定量描述,分析其失稳演化过程。研究结果表明:轴向压载条件下混凝土试件的应力与声发射振铃计数、能量释放随时间的变化规律具有一致性,声发射定位点主要在剪应力集中区形成宏观“定位带”与混凝土裂缝发展及破坏表现一致,可根据声发射事件活跃度量化判断混凝土受载阶段,反映混凝土失稳临界特征,对桩基混凝土服役监测具有重要意义。

The concrete of bridge pile foundations always bear excessive axial loads,and accompanying with its internal failure and crack process,elastic waves will be emitted.In order to quantify the characteristics of the entire instability evolution process of concrete,the temporal and spatial evolution characteristics of acous-tic emission in the whole loading process of concrete specimens drilled in situ from bridge pile foundation structures were studied and synchronous monitoring tests of axial compression and acoustic emission were con-ducted.The relation between the whole process of compressive instability and the acoustic emission ringing counts,energy release,focal locations and other characterization parameters were analyzed.Then,a quantita-tive description of the correlation between the loading process and acoustic emission characteristics was ob-tained,and its instability evolution process was analyzed.The results indicated that the stress of concrete specimens under axial compression was consistent with the change law of the acoustic emission ringing counts and energy release with times,and the acoustic emission positioning points mainly located in a macro“positio-ning zone”in the shear stress concentration area,which was consistent with the development and failure of concrete cracks.The loading stage of concrete could be quantitatively judged according to activity of acoustic emission,which could reflected the critical characteristics of concrete instability,and was of great significance to service monitoring of pile foundation concrete.