Abstract:

The portal section of Dongchongli tunnel has the characteristics of large crosssection, shallow cover and severe asymmetrical loading. The major features of the geological conditions along the tunnel include sandy slate containing metamorphic sandstone, severe variation of strata inclinations, development of rock joint and crack, weathered and fractured rock and ductile deformation. Analysis is made on the causes for the tunnel collapse, and the principle for the selection of the collapse treatment methods and the collapse treatment technologies are presented in detail in this paper. In addition, the experience obtained from the collapse treatment is summarized on basis of analysis on the collapse treatment results. The paper can provide significant references for similar tunnel collapse treatment in the future.

Key words: Dongchongli tunnel, tunnel collapse, large crosssection, severe asymmetrical loading, soft and weak surrounding rock, top heading and bench method, grouting through small duct, grouting from ground surface