Experience with construction of a free-flow tunnel at the Tatevsk hydroelectric plant (Armenian SSR)

Conclusions

• 1. According to the current norms, tunnel linings are designed for the readiness stage, that is, for the most advantageous operating conditions, without taking into consideration the stage during which they act. The main cause of crack formation in tunnel linings is the tardy application of the arch grouting. In this connection the SNiP norms for hydraulic tunnels should include a paragraph establishing rigorously the time of initiation of the arch grouting.

• 2. Taking into consideration the fact that the rock pressure increases very rapidly and that the concrete in the linings cannot so soon attain the design pressure, it is necessary to use special hydraulic concretes which can reach a high strength in a short period.

• 3. The rock pressure may be greatly reduced by supporting the excavation with anchored elements. Careful experimental investigations conducted at the tunnels now under construction may give a comprehensive picture of the dynamics of the increase of the rock pressure and behavior of the concrete lining (deformations and stresses) before and after the application of grouting in the space behind the arch.