Since concrete infrastructure may lose its expected physical and functional properties over time, accurate inspection and assessment of such infrastructure systems is necessary to ensure safety and serviceability and prevent unsafe working conditions and the occurrence of hazards. In this paper, an experimental investigation was conducted on several concrete specimens under uniaxial compression to fully explore the fracture process and mechanical characteristics of concrete materials under compressive loading conditions. More specifically, a high-resolution industrial camera and a real-time geophysical acquisition system were employed to capture the fracture process and the microseismic (MS) and electromagnetic emission (EME) signals simultaneously. Based on digital image processing, a robust crack extraction algorithm was proposed for automatically identifying cracks on a concrete surface at the pixel level, and then two novel crack features were introduced to depict the dynamic crack propagation process quantitatively. Then, the correlation between MS, EME, stress drop and dynamic crack evolution characteristics was analyzed. The results indicate that: (1) the MS and EME signals of the concrete specimens have good consistency in the time domain, especially in the fully fractured stage; (2) the crack area, to a certain extent, can reflect the stress drop of a concrete specimen under the compression fracture process; (3) the crack propagation velocity parallel to the loading axis (along the vertical direction) is faster than that the perpendicular one to the loading axis (along the horizontal direction); and (4) the crack area, stress, MS signal, and EME signal reach their peak values nearly simultaneously. Finally, a novel mesh-free numerical model based on peridynamic (PD) theory was established to simulate the fracture process, and the displacement fields were presented to further reveal the failure mechanism of concrete under compressive loading.

由于混凝土基础设施可能会随着时间的流逝而失去其预期的物理和功能特性，因此必须对此类基础设施系统进行准确的检查和评估，以确保安全性和可维修性，并防止不安全的工作条件和危害的发生。本文在单轴压缩下对几个混凝土试件进行了实验研究，以充分探索在压缩载荷条件下混凝土材料的断裂过程和力学特性。更具体地说，采用了高分辨率的工业相机和实时地球物理采集系统来同时捕获裂缝过程以及微地震（MS）和电磁发射（EME）信号。基于数字图像处理，提出了一种鲁棒的裂纹提取算法，用于在像素水平上自动识别混凝土表面的裂纹，然后引入两个新颖的裂纹特征来定量描述动态裂纹扩展过程。然后，分析了MS，EME，应力降与动态裂纹扩展特征之间的相关性。结果表明：（1）混凝土试样的MS和EME信号在时域上具有良好的一致性，尤其是在完全断裂阶段。（2）裂缝面积在一定程度上可以反映出混凝土试样在压缩断裂过程中的应力降；（3）平行于加载轴（沿垂直方向）的裂纹扩展速度快于垂直于加载轴（沿水平方向）的裂纹扩展速度；（4）裂纹面积，应力，MS信号和EME信号几乎同时达到峰值。最后，建立了一种基于蠕动（PD）理论的新型无网格数值模型来模拟断裂过程，并给出了位移场，以进一步揭示混凝土在压缩载荷作用下的破坏机理。