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| A disaster with water inrush based on energy theorem in tunnels under saturated sandy stratum |
| QIU Wenge1,2, HUANG Haiyun1, YAN Feiyue1, SUN Keguo1*
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1. Key Laboratory of Transportation Tunnel Engineering, Ministry of Education, Southwest Jiaotong University, Chengdu 610031, Sichuan, China;
2. Chengdu Tianyou Tunnelkey Co., Ltd., Chengdu 610031, Sichuan, China |
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Abstract The paper aimed to investigate the natural mechanism for this water inrush and mud outburst disaster in certain subway tunnels by energy theorem. The fundamental reason why this disaster was so large(approximately 11 679 m3)was that the equilibrium of the surrounding rock around the tunnel face was broken, and thus the volume of potential energy was transformed into kinetic energy and released instantaneously. Based on the field survey, some reasons were concluded as follows: the geological tectonic profile seemed like a “funnel”, where stress concentration was obvious; the tunnels crossed the bottom of the “funnel”; the weak and thin strongly-weathered tuff with many cracks located on the crown; the “funnel” stratum could collect a large amount of rainwater, and before this disaster, the rainfall resulted in the medium-coarse sand being saturated, so the water-head rose, seepage force increased, and the surrounding rock was weakened. These conditions could be classified into DI space. It could be seen from the numerical simulation that, the tunnel face applied by seepage force was unstable when strengthened by leading injected conduit whereas by taking account of the influences of seepage function, the tunnel face strengthened by steel piles could keep stable. By comprehensively analysis, it could conclude that the natural reasons for this disaster were that the combined effects consisting of increasing water pressure, concentrated stresses, seepage forces, applied to the degrading rocks, and then the potential energy transforming into kinetic energy formed this disaster on a large scale.
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Received: 12 January 2021
Published: 20 March 2021
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