影响跨孔雷达层析成像效果的几个因素

Several Factors Affecting Cross-Hole Radar Tomography

利用合成数据研究并讨论了影响基于射线的跨孔雷达走时层析成像的几个重要因素，包括射线覆盖角度、正则化因子以及测量装置排布等。对比不同射线覆盖角度下层析成像的结果表明，40°～70°为跨孔雷达层析成像的最佳角度。对比不同正则化因子情况下层析成像的结果表明，正则化因子太小或太大，都会导致反演结果与实际模型差别较大，因此选择合适的正则化因子对反演成像极其重要。通过研究水平和不同倾斜异常体的层析成像结果以及波场快照发现，由于发射和接收装置通常放置在2个平行的钻孔中，使得射线主要在近水平方向上传播，因此横向异常体的反演效果好，而纵向或高角度异常体的反演效果不佳，且反演出的异常范围要比实际尺度大。

Several factors affecting cross-hole radar tomography were discussed by using synthetic data, including the ray coverage angle, the regularization factor k, as well as the measurement configuration. The ray coverage angle was investigated and is found that 40 - 70 degree is most fitted angle for tomography. If the regularization factor k is too small or too large, the inverted image will differ from model too much. Therefore, the choice of the fitted regularization factor is very important. By studying the horizontal and various oblique anomaly bodies and related wavefield snapshots, it is found that since both the transmitter and the receivers are located in two parallel holes, the rays are mainly along the horizontal direction to propagate, the horizontal anomaly is well imaged, but the vertical or highly angle anomaly cannot be imaged well.