箱梁预应力管道内空洞探地雷达有限元正演模拟

箱梁预应力管道注浆不密实导致梁体预压应力瞬间失效,从而造成梁体突然断裂坍塌的危害。为了更准确地检测箱梁预应力管道内注浆不密实缺陷,建立箱梁预应力管道内空洞物理模型,分析在探地雷达二维及三维探测下钢筋、管道部分注浆及管道充水条件下反射波信号的成像特点。基于改进Sarma吸收边界的有限元法计算公式,编制MATLAB程序对箱梁预应力管道内不同大小的空洞进行正演模拟。通过模型试验和数值模拟对比分析,结果表明:探地雷达三维探测能识别钢筋和空洞的分布,更全面地反映不同病害的形态特征;有限元模拟分析表明回波信号出现的时间、回波强度、双曲线的曲率及延长度均与空洞几何尺寸有关。空洞在模拟和试验探测的结果均为"弧形",验证了数值模拟方法的可行性,为实际工作提供指导依据。

Finite Element Method Forward Simulation for Ground Penetrating Radar of Cavity in Prestressed Pipeline of Box Girder

The uncompactness grouting of box girder prestressed pipes results in the instantaneous failure of the prestressed stress, which causes the damage of the sudden fracture and collapse of the girder body.In order to detect the non-compactness of grouting in box girder prestressed pipes more accurately, a physical model of cavities in box girder prestressed pipes was established, and the imaging characteristics of reflected wave signals under two-dimensional and three-dimensional ground penetrating radar detection of reinforcing bars, partial grouting and water-filling conditions were analyzed. Based on the finite element method calculation formula of improved Sarma absorbing boundary, the forward simulation of cavities in box girder prestressed pipes with different sizes were carried out by using the Matlab program.Through the comparison and analysis of model test and numerical simulation,the results show that: the three-dimensional detection of ground penetrating radar can identify the distribution of reinforcement and cavities, and more comprehensively reflect the morphological characteristics of different diseases.The finite element simulation analysis shows that the time of echo signal, echo intensity, hyperbolic curvature and elongation are all related to the geometrical size of the cavity. The results of both simulation and test detection are "arc", which verifies the feasibility of the numerical simulation method and provides guidance for practical work.