Excavation characteristics of large-span shallow buried tunnel at soft-hard geological interface
When a large-span shallow buried tunnel passes through surrounding rock with non-uniform hardness,keeping stability becomes more difficult due to the large difference in mechanical properties of rock masses on the two sides of the soft-hard geological interface.Taking Zhoujiachong Tunnel of Liling-Loudi Expressway in Hunan Province as the research background,this study analyzes and compares the deformation and support force of surrounding rock under different inclination angles of geological interface by three-dimensional numerical simulation.The results show that the change of inclination angle of the geological interface makes the surrounding rock near the interface show agitation mutability in displacement curve and forms an inflection point.With the increase of the inclination angle of the interface,the area of the tension zone decreases gradually,while the area of the compression zone increases gradually.The surrounding rock at the arch side is most prone to plastic failure.As the excavation distance increases,the plastic zone of surrounding rock expands.When the inclination angle of the soft-hard geological interface is low,the phenomenon of plastic zone expansion is particularly evident.
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