混凝土表面开口裂缝对近表面声波影响
The influence of surface opening cracks on the sound wave near concrete surface

基于混凝土近表面不同波型的声速，分析开口裂缝对声波的影响。有限元仿真结果表明，激励源辐射的初始纵波P经裂缝端点衍射产生纵波P-P与横波P-T，P-T以一定的角度射向混凝土表面经模式转换产生纵波P-T-P；初始横波T在裂缝端点衍射产生纵波T-P与横波T-P；初始瑞利波R在裂缝端点衍射后除了产生纵波R-P与横波R-S外继续沿着固体表面传播（R-R）。在此基础上，基于变型波到达接收阵元的时刻定量检测裂缝的深度，检测结果较单面平测法具有更高的信噪比与检测精度，可辅助单面平测法更精确地定量检测混凝土开口裂缝的深度。
Based on the velocities of different wave modes near concrete surface,the influences of surface-crack on these wave modes are analyzed.Finite Element Method (FEM) simulation results show that the original longitudinal wave P is diffracted at crack tip to generate longitudinal wave P-P and transverse wave P-T,and the latter propagates onto surface with a certain angle of incidence to result in a new longitudinal wave P-T-P;the original transverse wave T is diffracted at crack tip to generate longitudinal wave T-P and transverse wave T-T;the original Rayleigh wave R is diffracted at crack tip to generate longitudinal wave R-P and transverse wave R-T,and continues to propagate along the solid surface (R-R).On the basis of the simulation results,the multi-mode wave method by measuring the arrival times of variant waves to receiver can be utilized to measure the depth of surface crack with higher signal-to-noise ratio and more precise resolution compared to the single plane method.