Punching shear model tests on defective mountain tunnel lining

Abstract

Some tunnels constructed by the conventional excavation method have defects like an insufficient lining thickness and voids behind the lining. It is thought that the structural strength of defective lining becomes lower than that of sound lining against the punching shear stress caused by loosening pressure. Therefore, we performed model tests to quantitatively estimate the influence of initial defect on the structural strength of lining under the punching shear stress. We found that defective lining was brittle in its destructive behavior against the punching shear stress and the structural strength became smaller than that of sound lining when the lining thickness was about half that of sound lining. We proposed a criterion of countermeasures for tunnel lining against punching shear stress based on these tests.