不同初始孔隙率混凝土的声发射试验及损伤分形特征分析

为探索混凝土声发射信号特征参数与其损伤的演化关系，对单轴多级循环加载条件下的不同初始孔隙率混凝土试件进行了声发射试验.引入活跃系数对声发射现象发生的活跃程度进行表述，提出基于声发射能量评价混凝土服役状态的方法，分形理论分析了混凝土破坏过程中声发射能量分形维数（关联维数）的演化特征.结果表明:不同初始孔隙率混凝土试块声发射能量和声发射能量关联维数随加载进程的变化趋势基本相同，失稳破坏的临界位置相当.在混凝土破坏过程中，当声发射能量峰值下降后再次激增、能量均值超过100 m V· ms且活跃系数在20~70范围内连续放缓的现象出现时，预示混凝土材料的破坏.声发射能量关联维数随加载进程下降表明出现损伤，持续下降后并呈水平趋势，标志混凝土结构临近极限承载力. 

Acoustic Emission Test and Damage Fractal Characteristics Analysis of Concrete with Different Initial Porosity

In order to explore the relationship between the acoustic emission (AE) signal''s characteristic parameters and the damage evolution of concrete, the acoustic emission test on concrete specimens with different initial porosities under uniaxial cyclic loading conditions. The activity coefficient was introduced to express the activity level of acoustic emission. A method of evaluating concrete working state based on acoustic emission energy was put forward. Fractal dimension theory was used to analyze the acoustic emission energy sequence evolution characteristics of concrete with different initial porosities. The results showed that the correlation dimension of acoustic emission energy and acoustic emission energy of concrete blocks with different initial porosities was basically the same as that in the loading process, and the critical position of instability failure was equivalent. The concrete damage could be predicted when the peak of acoustic emission energy dropped again, the average energy was more than 100 m V·ms and the activity coefficient slowed down continuously within the 20~70 range. The acoustic emission energy correlation dimension decreased continuously and showed a horizontal trend signaling the ultimate bearing capacity of concrete structure.