Anomaly Prediction Ahead Tunnel Face Using Tunnel Electrical Resistivity Prospecting System (TEPS) in Danyang
- Chang-Ho Hong (Korea Advanced Institute of Science and Technology) | Gye-Chun Cho (Korea Advanced Institute of Science and Technology) | Eun-Soo Hong (Korea Advanced Institute of Science and Technology) | Seng-Hyoung Baak (HBC Inc.) | Hee-Hwan Ryu (Korea Electric Power Research Institute)
- Document ID
- International Society for Rock Mechanics and Rock Engineering
- ISRM European Rock Mechanics Symposium - EUROCK 2017, 20-22 June, Ostrava, Czech Republic
- Publication Date
- Document Type
- Conference Paper
- 2017. Elsevier Ltd. Permission to distribute - International Society for Rock Mechanics and Rock Engineering
- Tunnel ahead prediction, anomalies, anomalies, South Korea, South Korea, TEPS, TEPS, Tunnel ahead prediction, anomalies, South Korea, Tunnel ahead prediction, TEPS
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Anomalies in tunnel ahead cause various problems, such as ground settlement, sinkholes and groundwater inflow during tunneling. Therefore, the accuracy of predictions of the location and size of anomalies is essential for safe tunnel excavation processes. TEPS, known as a tunnel-ahead prediction method, analyses electric fields through the tunnel-ahead rock mass between sensors attached to the tunnel face. TEPS requires approximately two hours overall for measurements and analyses, and it predicts 3-4 times the tunnel diameter ahead of the tunnel face. In this study, tunnel-ahead prediction tests are conducted using TEPS in a railway tunnel located in Danyang, South Korea. The tunnel passes through limestone regions, and hard rock region occasionally appears. The tunnel was excavated safely based on the predicted information.
The existence of anomalies such as cavities and faults in front of a tunnel face can cause surface settlement and sinkholes due to cavity collapse and the inflow of geo-materials (sand, silt, and clay) inside the cavities and faults. These phenomena increase the construction cost and time and can cause casualties.
Settlements in squeezing ground have been measured , and the effects of fault angles, the tunnel diameter, and the distance between the tunnel face and a fault has also been simulated . Settlements in different compositions of clay and Trakya formations were also measured .
Most bedrock in South Korea is granite. However, the bedrock in some regions, such as Danyang and Jechun, is limestone. Sinkholes are generated by collapsing cavities induced by groundwater and soil, and groundwater which fills cavities flows into tunnels in limestone regions. For traffic and metropolitan tunnels, additional loadings such as traffic and trains collapse cavities beneath pavement and rails, respectively. And also sudden changes of phase in tunnel face can cause collapse of tunnel. Therefore, it is necessary to forecast ahead of tunnel face for safe tunnel construction. The tunnel electrical resistivity prospecting system (TEPS) was developed to prevent such damage, and experimental tests were performed in regions of marble to predict anomalies ahead of a tunnel face in Danyang, South Korea.
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