It is tried to study the acoustic events occurring in the samples during the test, and their locations are investigated. The samples are loaded uniaxially or biaxially with different stress rates. A circular hole is drilled in the center of each sample. For this purpose, 33 cube samples of three different material types including sandstone, concrete, and cement-plaster mortar are prepared. In this research, a study is conducted on the rock samples by a numerical method to investigate the damaged zone caused by the excavation of circular space on it. This method is based on receiving the elastic waves that are produced by deformation and cracking of the rock mass around the underground excavation. This study contributes to a more accurate estimation of damage to tunnel lining caused by severe deformation of the surrounding rock mass.One of the methods used to investigate the damaged zone in rock structure is the acoustic emission method. It was then concluded that the normal contact stiffness is on the order of 1 GPa/m, especially for the weak rock mass investigated. The analysis result demonstrated that the strain-softening behaviour produces significantly large floor heave, indicating that in the physical test, such severe strain softening did not occur. Furthermore, the effect of strain-softening behaviour was examined, implementing the most noticeable strain softening curve observed among uniaxial tests conducted in the previous experiment. It has been also clarified that the magnitude of the horizontal displacement is hardly affected by the internal friction angle, implying the validity of the estimation. For k n exceeding the value, both the horizontal displacement and the magnitude of floor heave deviate from the experimental result. As k n is increased, the displacement becomes larger, and it was found that the analysis result agrees with the experiment the most closely when k n = 1 GPa/m. The analysis result indicated that when k n is less than 1 MPa/m, the horizontal displacement of the lining is much smaller than the experimental result. Elasto-plastic analyses were then performed while changing the normal stiffness k n of interface elements representing the contact. For the purpose, a numerical model was constructed that reproduces a previously-conducted physical test investigating tunnel lining damage due to the degradation of the surrounding weak rock mass.

The present study aims to quantify the normal contact stiffness between the concrete lining of a mountain tunnel and the surrounding weak rock mass, which has been never seriously investigated in the previously-performed numerical simulations.

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