Abstract:

The fullscale tests are carried out on 6 groups of shield tunnel lining segment with initial damage so as to learn the influence of initial damage on mechanical properties of shield tunnel lining segment. And then the failure process, failure mode, ultimate bearing capacity, deformation law and propagation mechanism of initial crack of specimens are studied and analyzed considering the influence of the position of initial damage and the decrease of the effective area of steel bars around initial damage. The testing results show that: 1) The initial damage has little influence on the ultimate bearing capacity of shield tunnel lining segment; but it has a significant influence on its normal function. 2) The decrease of effective area of steel bars around initial damage not only affects the normal function of shield tunnel lining segment but also affects ultimate bearing capacity significantly (reduction). 3) The influence of initial damage on shield tunnel lining segment can be reduced by increasing the axial force. 4) The influence of initial damage at loading point is more obvious than that at midspan section. 5) The crack propagation path is nearly a line that grows radially or toward to the midspan section. The related research results can provide reference for establishing the health assessment and predicting theory of the shield tunnel structure during its longtime service, as well as for further conducting the numerical simulation and the ultimate bearing capacity analysis of shield tunnel with damage and defects.

Key words: shield tunnel, initial damage, fullscale test, effective area of steel bars, ultimate bearing capacity, deformation, crack propagation