Analysis on the Cause for Early Open Jointing Disease in the Monolithic Ballast Bed of Metro Shield Tunnel
The finite element model of monolithic ballast bed in metro shield tunnel is established.By applying the equivalent cooling load,the causes for the open jointing disease of monolithic ballast bed in shield tunnel are analyzed.The results show that the stress level on monolithic ballast bed and shield segment is positively correlated with the early shrinkage degree and age growth of concrete;under the action of concrete shrinkage stress,the interface damage is easy to occur at the end of the bonding interface between the ballast bed and the shield segment,and even the open jointing disease may occur.The early interface damage of the ballast bed is mainly a composite failure mode of tension and shear,and the interlayer damage will occur when the equivalent cooling load reaches 2℃.It is suggested to carry out research on the value of concrete shrinkage load in ballast bed and optimize the monolithic ballast bed structure of shield tunnel.
ballast bed open jointingmetro shield tunnelconcrete shrinkage
NETL
NSTL
万方数据
