库尉输水隧洞塌方机制分析及加固效果评价

ANALYSIS OF THE COLLAPSE MECHANISM OF THE KUYU WATER CONVEYANCE TUNNEL AND ASSESSMENT OF THE EFFECTIVENESS OF ITS GROUND REINFORCEMENTS

库尉输水隧洞前段地下水位远高于洞顶(均在洞顶10 m以上),洞内呈淋雨状,施工过程中塌方事故频发,多处洞顶形成塌方廊道,给工程施工和长期运行造成了隐患。在对塌方事故调查和分析的基础上,通过有限差分软件FLAC3D对其坍塌机制进行系统的研究,并对典型塌方洞段的加固效果进行论证。研究表明:(1)地层岩性是该隧洞塌方事故频发的内在原因,地下水进一步增加了坍塌的可能性(致使洞周变形增加了约2.0倍);(2)初期支护不及时和开挖循环进尺过长是塌方事故发生的直接原因(致使洞周变形分别增加了约0.8和0.2倍);(3)加固处理方案的合理性和施工质量的可靠性对隧洞的安全稳定性至关重要。

The groundwater level around the front section of the Kuyu water conveyance tunnel is far above the ceiling of the tunnel, causing groundwater infiltration to be so severe that it 'rains' constantly in the tunnel. During construction, accidental collapse occurred often and many collapse galleries were formed above the tunnel, which brought serious problems and delays to the construction. Based on investigation and analysis of some of the collapse incidents, the failure mechanism was studied systematically using the finite difference software FLAC3D, and the effectiveness of ground reinforcement on a typical collapse section was assessed. The study showed that the formation lithology was the internal cause of the collapses, and that the groundwater further exacerbated the instability potential, with the deformation almost triple that under anhydrous conditions. Lack of timely initial support and too large an advance per excavation cycle were two direct causes of tunnel collapses, as these practices caused additional deformation of 80% and 20% respectively. The rationality of the ground reinforcement schemes and the quality of construction of the ground support system are crucial to the long-term stability of the tunnel. © 2015, Science Press. All right reserved.