Evolution Characteristics of Mechanical Behavior for Secondary Lining of Large-span Tunnel During Construction
In order to study the evolution characteristics of mechanical behaviour for secondary lining of large-span tunnel during construction,the field test and numerical calculation are applied based upon realistic project.The distribution state and development rule of secondary lining's internal force and contact pressure are obtained through comparison,and the load bearing ratio and construction timing of secondary lining can be evaluated accordingly to provide reference for the design of highway tunnel secondary lining.The result shows that the numerical calculation result is similar to the field test,and the bearing ratio of secondary lining is close to 0.4.After the secondary lining is cast,the volumetric expansion of the structure induced by hydration reaction has a significant effect on its mechanical behavior,and the influence of hydration reaction reaches its peak within 3 d and lasts for 2-3 weeks.According to the field test,the contact pressure on tunnel vault,side walls and tunnel invert tend to stabilize within the range of 0-20,70-80 and 5-10 kPa respectively after the hydration reaction,while the contact pressure on arch foot shows a trend of first decreasing and then increasing as the construction progresses,which finally reaches a level around 200 kPa.The internal force of secondary lining grows continuously as the construction progresses;the axial compression force on tunnel vault,side walls and tunnel invert are 450,140 and 200 kN respectively.The bending moment is relatively minor on each part of the structure,therefore,the secondary lining has sufficient safety redundancy.According to the numerical calculation,the growth rate of contact pressure on arch foot is relevantly faster when the casting section of the second lining is within 15 m from the research section.When the casting section of the second lining passes research section by over 45 m,the contact pressure between linings and the internal force of the second lining tend to stabilize.
tunnel engineeringmechanical behavior of liningfield testsecondary lininglarge-span tunnelconstruction period
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