Empty region detection has wide-rang application in geotechnical engineering, such as resource exploration and tunnelling engineering. The traditional geophysical exploration methods require plenty preliminary investigations, which are also greatly affected by various parameters and limited by wave velocity difference. Therefore, this paper proposes a new method for empty region identification in the two-dimensional complex structure. It utilizes the improved A* search algorithm to search the shortest wave path, and matches with the potential empty region to estimate the size and position of the cavity. The numerical analysis and laboratory test were carried out to evaluate this method. The effectiveness of the method is proved by the results of holes in the detected area with different diameters, positions and shapes. The reliability of the method is demonstrated by the search results of arrival time difference data with errors. The results of laboratory test further verify the feasibility of the method. This paper provides a new idea for the empty region detection and lays the foundation for three-dimensional empty space detection, which is also suitable for testing of materials and machinery.

空区检测在岩土工程中有着广泛的应用，例如资源勘探和隧道工程。传统的地球物理勘探方法需要大量的前期调查，而且受各种参数的影响很大，受波速差的限制。因此，本文提出了一种二维复杂结构中空域识别的新方法。它利用改进的A*搜索算法搜索最短波路径，并与潜在的空区域匹配来估计空腔的大小和位置。进行了数值分析和实验室测试以评估该方法。通过检测区域不同直径、位置和形状的孔洞结果证明了该方法的有效性。有误差的到达时间差数据的搜索结果证明了该方法的可靠性。实验室测试结果进一步验证了方法的可行性。本文为空区检测提供了一种新的思路，为三维空区检测奠定了基础，也适用于材料和机械的检测。