Experimental Research on Mechanical Response and Safety Charac-teristics of Surrounding Rock and Lining of Unilateral Extension of Highway Tunnel
In order to study the construction mechanical behavior and safety of highway tunnel in unilateral expansion construction,the surrounding rock stress,lining stress,axial force,bending moment and safety of highway tunnel in unilateral expansion construction are studied by model test.The results are as follows:① When the tunnel is expanded,the strength of surrounding rock affected by secondary disturbance decreases sharply,and the damage degree increases obviously,especially in the area of the extension side arch and vault.②In the process of tunnel expansion,the stress transfer will increase the compressive stress of the old lining;The new lining gradually bears the load of surrounding rock after installation,and its stress increases significantly,especially at the position of vault and arch.③The safety factor of most lining models is less than 2.0,especially the arch foot is the most vulnerable to instability,and the arch foot area requires additional reinforcement measures to prevent potential structural instability and damage.④According to the guidance of the test data,the method of advance support and upper and lower steps is proposed,and the dregs backfill is used as the construction platform of tunnel upper step excavation to realize safe and efficient construction.
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