@Article{cmc.2020.07946,
AUTHOR = {Abierdi, Yuzhou Xiang, Haiyi Zhong, Xin Gu, Hanlong Liu, Wengang Zhang},
TITLE = {Laboratory Model Tests and DEM Simulations of Unloading- Induced Tunnel Failure Mechanism},
JOURNAL = {Computers, Materials \& Continua},
VOLUME = {63},
YEAR = {2020},
NUMBER = {2},
PAGES = {825--844},
URL = {http://www.techscience.com/cmc/v63n2/38546},
ISSN = {1546-2226},
ABSTRACT = {Tunnel excavation is a complicated loading-unloading-reloading process 
characterized by decreased radial stresses and increased axial stresses. An approach that 
considers only loading, is generally used in tunnel model testing. However, this approach is 
incapable of characterizing the unloading effects induced by excavation on surrounding rocks 
and hence presents radial and tangential stress paths during the failure process that are different 
from the actual stress state of tunnels. This paper carried out a comparative analysis using 
laboratory model testing and particle flow code (PFC<sup>2D</sup>)-based numerical simulation, and shed 
light upon the crack propagation process and, microscopic stress and force chain variations 
during the loading-unloading process. The failure mode observed in the unloading model test 
is shear failure. The force chains are strongly correlated with the concrete fracture propagation. 
In addition, the change patterns of the radial and tangential stresses of surrounding rocks in 
the broken region, as well as the influence of the initial stress on failure loads are revealed. 
The surrounding soil of tunnel failure evolution as well as extent and shape of the damage 
zone during the excavation-induced unloading were also studied.},
DOI = {10.32604/cmc.2020.07946}
}