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The tunnel seismic method allows for the detection of the geology in front of a tunnel face for the safety of tunnel construction. Conventional geophones have problems such as a narrow spectral width, low sensitivity, and poor coupling with the tunnel wall. To tackle issues above, we propose a semi-automatic coupling geophone equipped with a piezoelectric sensor with a spectral range of 10-5000 Hz and a sensitivity of 2.8 V/g. After the geophone was manually pushed into the borehole, it automatically coupled with the tunnel wall under the pressure of the springs within the device. A comparative experiment showed that the data spectrum acquired by the semi-automatic coupling geophone was much higher than that of the conventional geophone equipped with the same piezoelectric sensor. The seismic data were processed in combination with forward modeling. The imaging results also show that the data acquired by the semi-automatic coupling geophone were more in line with the actual geological conditions. In addition, the semi-automatic coupling geophone's installation requires a lower amount of time and cost. In summary, the semi-automatic coupling geophone is able to efficiently acquire seismic data with high fidelity, which can provide a reference for tunnel construction safety.
Yao Wang; Nengyi Fu; Zhihong Fu; Xinglin Lu; Xian Liao; Haowen Wang; Shanqiang Qin. A Semi-Automatic Coupling Geophone for Tunnel Seismic Detection. Sensors 2019, 19, 3734 .
AMA StyleYao Wang, Nengyi Fu, Zhihong Fu, Xinglin Lu, Xian Liao, Haowen Wang, Shanqiang Qin. A Semi-Automatic Coupling Geophone for Tunnel Seismic Detection. Sensors. 2019; 19 (17):3734.
Chicago/Turabian StyleYao Wang; Nengyi Fu; Zhihong Fu; Xinglin Lu; Xian Liao; Haowen Wang; Shanqiang Qin. 2019. "A Semi-Automatic Coupling Geophone for Tunnel Seismic Detection." Sensors 19, no. 17: 3734.
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.
Yao Wang; Nengyi Fu; Xinglin Lu; Zhihong Fu. Application of a New Geophone and Geometry in Tunnel Seismic Detection. Sensors 2019, 19, 1246 .
AMA StyleYao Wang, Nengyi Fu, Xinglin Lu, Zhihong Fu. Application of a New Geophone and Geometry in Tunnel Seismic Detection. Sensors. 2019; 19 (5):1246.
Chicago/Turabian StyleYao Wang; Nengyi Fu; Xinglin Lu; Zhihong Fu. 2019. "Application of a New Geophone and Geometry in Tunnel Seismic Detection." Sensors 19, no. 5: 1246.