裂缝宽度对探地雷达波场影响的对比分析

通过理论分析、数值模拟和物理模拟实验，研究了地下隐蔽垂直裂缝宽度不断扩展时，裂缝顶部散射波振幅的变化规律.研究表明：1）当裂缝宽度小于第一菲涅尔带直径时，采用探地雷达图像无法直接确定裂缝宽度.但裂缝顶部散射波振幅随裂缝宽度变大而增强，特别是当裂缝宽度小于二分之一第一菲涅尔带直径时，裂缝宽度与裂缝顶部散射波振幅成近似线性关系；2）当裂缝宽度约等于第一菲涅尔带直径时，振幅达到极大值；3）超过第一菲涅尔带直径后振幅逐渐衰减，然后趋于一个稳定值，此时从探地雷达图像可以直接识别裂缝宽度.研究成果可用于识别地下隐蔽裂缝及定量估计裂缝宽度.

Comparative analysis on response of ground penetrating radar wave field to crack width

Through theoretical calculation, numerical simulation and physical experiments, we studied the variation of amplitudes of the diffracted wave at location of the top point of the crack with different width of vertical crack which is in the underground medium. The results show that: (1) Width of crack less than the diameter of the first Fresnel zone is not able to be measured directly from the image of ground penetrating radar. But with the increase of the width of crack, the amplitude of the diffracted wave is continuously enhanced. Especially, when the width of crack is less than half the diameter of the first Fresnel zone, the amplitude of the diffracted wave versus the width of crack has the approximate linear relationship. (2) When the width of crack is approximately equal to the diameter of first Fresnel zone, the amplitude reaches the maximum. (3) After that the amplitude decrease gradually and until it be stable to a constant value as width of crack is far more than the first Fresnel zone and the width crack is able to be measured directly from theimage of ground penetrating radar. The research results can be used in recognizing the underground crack and quantitatively estimating the width of the crack.