State Key Laboratory of Power Transmission Equipment and System Security and New Technology, Chongqing University, No. 174 Shazhengjie, Chongqing 400044, China.
School of Electrical Engineering, Chongqing University, No. 174 Shazhengjie, Chongqing 400044, China.
Sensors (Basel). 2019 Mar 12;19(5):1246. doi: 10.3390/s19051246.
Seismic imaging is the most effective geophysical method and has been extensively implemented to detect potential geological hazards in tunnels during construction. The coupling of geophones and the design of geometry in tunnels are the two major challenges. To ensure successful coupling, a high-sensitivity semi-automatic coupling geophone with a broadband was designed. In practice, this geophone is attached with a wheel and two springs. Once inserted into the borehole, an automatic coupling action occurs. This semi-automatic coupling design within the geophone not only guarantees good coupling, but reduces the time and costs usually required to install a traditional geophone. In the use of geophones for tunnel seismic detection, we propose two new two-dimensional (2D) seismic geometries based on the two commonly used geometries. A test to assess the effectiveness of the qualities of imaging from four geometries was completed by comparing the results of the forward modeling of sandwich models. The conclusion is that the larger the horizontal offset of the layout geometry, the higher the resolution of the imaging; the larger the vertical offset, the weaker the mirror image. The vertical offset is limited due to the narrow tunnel condition. Therefore, the mirror effect cannot be entirely eliminated; however, it can be further suppressed by constructing 2D geometry. The two newly proposed 2D geometries caused the imaging arc of the inter-layer, but suppressed the mirror image. The mirror image added a significant number of errors to the data, which could misguide tunnel construction; therefore the new 2D geometries are more reasonable than the two most commonly used. We applied one of the two new 2D geometries that was more practical to an actual project, the Chongqing Jinyunshan Tunnel in China, and acquired high-quality seismic data using two semi-automatic coupling geophones. The detection results were essentially consistent with the excavation conclusions.
地震成像技术是最有效的地球物理方法，已广泛应用于隧道施工中探测潜在的地质灾害。在隧道中，地震检波器的耦合和几何设计是两个主要挑战。为了确保成功耦合，设计了一种具有宽带的高灵敏度半自动耦合检波器。在实践中，这种检波器附有一个轮子和两个弹簧。一旦插入钻孔，就会自动发生耦合作用。这种检波器内部的半自动耦合设计不仅保证了良好的耦合，还减少了安装传统检波器通常所需的时间和成本。在隧道地震检测中使用检波器时，我们基于两种常用的几何形状提出了两种新的二维（2D）地震几何形状。通过比较夹层模型正演建模的结果，完成了对四种几何形状成像质量有效性的测试。结论是，布局几何形状的水平偏移越大，成像分辨率越高；垂直偏移越大，镜像越弱。由于隧道狭窄，垂直偏移受到限制。因此，无法完全消除镜像效应；但是，可以通过构建 2D 几何形状进一步抑制镜像效应。新提出的两种 2D 几何形状引起了层间的成像弧，但抑制了镜像。镜像会给数据增加大量错误，可能会误导隧道施工；因此，新的 2D 几何形状比最常用的两种更合理。我们将其中一种更实用的新 2D 几何形状应用于一个实际项目，即中国重庆金云山隧道，并使用两个半自动耦合检波器获得了高质量的地震数据。检测结果与开挖结论基本一致。
