6. Conclusions
This study, while aiming to provide a direct solution of the number and width of the lining cracks, presents a numerical algorithm to simulate the cracking process of reinforced concrete lining for pressure tunnels. In contrast with the previous research, the discrete crack model is applied. The number and width of the lining cracks can be directly solved, by simultaneously considering the effect of several important factors, such as the WPCS and the heterogeneity of the lining tensile strength. The present algorithm can better capture the mechanical properties of the pressure tunnel and help provide a better insight into its working mechanism.
The numerical results show that with the increase in water pressure, the lining cracks appear progressively and the crack width gradually increases. However, when the water head reaches a certain value, the increase in crack width is not evident, while the crack number increases further. After the lining cracks, the lining displacement distribution is discontinuous and the steel bar stresses are not uniform. The steel bar stress near a crack is much greater than that in the intact concrete, due to which the steel bar stress is not uniform and the measured value is to a great extent determined by the position of the stress gauge. Moreover, the WPCS has a significant influence on the lining cracking mechanism and should not be neglected. When the WPCS is considered, the final crack number reduces considerably and the crack width evidently increases.
