基于多频钻孔声呐的溶洞探测方法研究

地下溶洞的形态及大小特征对该区域地质结构的稳定性计算和评价具有重要意义，而目前所使用的钻孔声呐法通用性低，很难同时满足探测精度和探测广度的需求。为此，在传统钻孔声呐法的基础上，提出了一种基于多频钻孔声呐的溶洞探测方法。该方法在考虑了不同频率对实际探测对象贡献大小的基础上，合成了多种频率的探测数据，有效解决了探测尺度和探测精度之间对立的问题。首先，推导了探测系统的最佳频率表达式，为优先和更大程度上体现不同频率对探测结果分析的影响提供基本参数，并构建了频率影响因子参数来描述固有频率与最佳频率之间的偏离程度；然后，在叠加了频率影响因子的基础上，综合合成了多种探测频率的探测数据，采用改进的频谱测距法完成了探测对象的精确测定；最后，在附加深度以及方位信息之后，实现了溶洞腔体形态的立体重建；并将该方法应用到了实际工程中，验证了方法的可行性和准确性。

Research on karst cavity detection method based on multi-frequency borehole sonar

The shape and size characteristics of underground cavity are of great significance to the stability calculation and evaluation of geological structure in the region. However, the borehole sonar currently used lacks universality and it is difficult to meet the requirements of both detection accuracy and detection range. Therefore, on the basis of traditional borehole sonar method, this paper proposes a new method of detecting cavity based on multi-frequency borehole sonar. With considerations given to the contribution of different frequencies to the actual detection object, this method synthesizes the detection data of various frequencies and effectively solves the problem of the opposition between detection scale and detection accuracy. Firstly, the optimal frequency expression of the detection system is derived to provide basic parameters to reflect the influence of different frequencies on the analysis of detection results to a greater extent, and the frequency influence factor parameter is established to describe the deviation degree between the natural frequency and the optimal frequency. Then, on the basis of superposition of the frequency influence factor, the detection data of various detection frequencies are synthesised, and detection objects are accurately measured by using the improved spectrum ranging method. Finally, after adding depth and azimuth information, the three-dimensional reconstruction of cavity shape is realized. The feasibility and accuracy of the method are verified by applying it to practical engineering projects.