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| Disaster caused by evolution of large karst caves in the upper part of an operating high-speed railway tunnel and its disposal scheme |
| WANG Lichuan1, 2, MA Xiangfeng2, WANG Huawu3, YANG Ling4, YAO Yunxiao5, GONG Lun2*, WANG Qiu6, LIU Ziqi7, FAN Yongjie1, ZHOU Baoan1
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| (1. China Railway Chengdu Bureau Group Co., Ltd.,Chengdu 610082, Sichuan, China; 2. School of Civil Engineering, Southwest Jiaotong University/Key Laboratory of Traffic Tunnel Engineering, Ministry of Education Chengdu 610031, Sichuan, China; 3. China Railway Kunming Bureau Group Co., Ltd.，Kunming 650011, Yunnan, China; 4. China Railway Beijing Engineering Bureau Group, Beijing 102308, China; 5. Yuqian Railway Co., Ltd., Chongqing 404100, China; 6. Chongqing Survey and Design Research Institute Co., Ltd., China Railway Second Institute, Chongqing 400023, China; 7. Karst Research Institute of Guizhou Normal University, Guiyang 550001, Guizhou, China) |
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Abstract This paper was based on the engineering practice of a large karst cave (this cave was revealed during the construction period) in the upper part of a high-speed railway tunnel in June 2019. The main situation of revealing karst cave and its change countermeasures, disasters and emergency measures during the operation period was introduced, and the mechanism of karst cave evolution disaster was analyzed through the inspection of each stage during investigation, design and construction. A consultation scheme combining “arch protection + strong blocking + reserved drainage + consolidation and lightweight compact backfilling” was put forward, which was on the basis of pointing out the shortcomings of the two drainage tunnel renovation schemes. The feasibility, working conditions, construction period, investment, risks, environmental impact and effect prediction was compared with the drainage tunnel scheme. Finally, a three-dimensional mode was established by FLAC3D to check the safety of tunnel. The research results were as follows: The karst cave with filling type was changed into water-filled and water-flowing type due to the construction tunnel. And water flowed into the karst cave by the type of runoff, which was formed by the dissolution gap, dissolution tank, pipeline between the surface and the karst cave during seasonal heavy rainfall. The disaster was formed by sediment entering the tunnel with the karst cave water-filled and water-flowing; the runoff field hydraulic channel was formed by the medium between the karst cave and the tunnel under the action of seasonal karst cave water-filled and water-flowing or even short-term pressure.The consultation scheme of "arch protection + strong blocking + reserved drainage + consolidation and lightweight compact backfilling” had significant advantages over the drainage tunnel scheme in terms of environmental protection, investment control, construction period and construction risks. It would necessarily lead to the evolution of disasters within a certain period of time after the completion of tunnel, by taking groundwater observation and water quantity estimation during the construction period as the basis for disposal of large karst caves and ignoring the induced evolution prediction of groundwater force field caused by engineering activities. So the disaster was appeared only after one and a half years of operation because of failure to maintain and construct the artificial drainage channel of groundwater with maintenance function. In addition, it was suggested that special measures of unit separation water prevention and drainage should be implemented for water-rich sections or potential water-rich sections when new tunnels were built.
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Received: 26 February 2020
Published: 25 May 2020
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WANG Lichuan, MA Xiangfeng, WANG Huawu, YANG Ling, YAO Yunxiao, GONG Lun, WANG Qiu, LIU Ziqi, FAN Yongjie, ZHOU Baoan. Research on disaster caused by evolution of large karst caves in the upper part of an operating high-speed railway tunnel and its disposal scheme[J]. Hazard Control in Tunnelling and Underground Engineering, 2020, 2(1): 20-33. |
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