Enhancing the safety management of NATM using the tunnel seismic prediction method: a case study
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CASE STUDY
Enhancing the safety management of NATM using the tunnel seismic prediction method: a case study Hong‑Kee Tzou1 · Tai‑Sheng Chu1 · Tai‑Yi Liu1 Received: 2 July 2020 / Accepted: 17 August 2020 © Springer Nature Switzerland AG 2020
Abstract Although NATM is widely applied in modern tunnel design and construction, tunnel construction is still deemed highly risky due to the unknown ground condition ahead of the excavation face. Faults, massive groundwater, fracture zones, and other factors might easily cause great danger to the excavation work. To enhance the safety management of NATM, the tunnel seismic prediction (TSP) method is introduced to help detect unstable ground conditions to prevent the happening of collapses or disasters during tunnel excavation. With the reflected seismic waves collected from several explosions, TSP could produce high-resolution simulated images that, with careful interpretation, will reveal the ground conditions ahead. In this paper, how TSP is incorporated with NATM for better construction safety is presented. Keywords Tunnel seismic prediction (TSP) · Safety · NATM
Introduction This study proposes using tunnel seismic prediction (TSP) to enhance safety management when building a tunnel. This study considers the Chungren Tunnel, which was built by the New Austrian Tunneling Method (NATM) and has a length of 4774 m and two tubes of width 11 m and height 14 m. This tunnel is a major part of Contract C1A, which is one of the nine civil construction contracts of an ongoing project named the “Suhua Highway Improvement Project.” According to the survey data, during the excavation work, the Hochung fault combined with a collapsed zone will be encountered at about tunnel mileage 0k + 820. Figure 1 shows the approximate location of the Hochung Fault and the collapsed zone. The abovementioned site includes the fault and poor ground conditions, which can cause a large disaster during * Tai‑Yi Liu [email protected] Hong‑Kee Tzou [email protected] Tai‑Sheng Chu [email protected] 1
New Asia Construction and Development Corporation, 15F, No. 760, Sec. 4, Pade Rd., Taipei City 10567, Taiwan, R.O.C.
tunnel blasting. In this project, the TSP method successfully detected and verified the exact location of the Hochung Fault and the collapsed zone. A small-scale collapse occurred when the first encounters with the Hochung Fault area. This failure case not only verified the accuracy of the TSP results but also significantly helped the engineers to increase the alertness on safety management and disaster prevention. It provided vital information to arrange and perform the followed soil reinforcing method before the tunnel excavation work.
Failure case with the collapse during excavation An unexpected collapse occurred during the tunnel excavation at the station of 0k + 814.9 (TR-162) dated November 4, 2015. The volume of the collapsed soil is 130 m3, with the 15 L/min of groundwater leakage. It is caused by the poor ground condition and failure of the preliminary liner system.
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