Abstract:

In this paper, comparison and contrast is made between field trials in tunnel sections with anchor bolts and those in tunnel sections without anchor bolts, with Taohuayu shallowcovered largespan smallspacing loess tunnel as an example, so as to study the supporting effect of systematic anchor bolts. The results show that: 1) The crown settlement of primary support in tunnel sections with anchor bolts is slightly smaller than that in tunnel sections without anchor bolts; 2) The effect of anchor bolts to improve the stress condition of the surrounding rock and primary support of the tunnel is insignificant; 3) The contact pressure between the surrounding rock and the primary support in tunnel sections with anchor bolts is smaller and more uniform than that in tunnel sections without anchor bolts. The authors suggest that the anchor bolts should be cancelled, while the anchor bolts on the sidewall of the proceding tunnel close to the small spacing may be kept so as to ensure the successful tunneling through weak zones. The paper can provide reference for the design and construction of similar shallowcovered largespan smallspacing loess tunnels in the future.

Key words: shallow cover lage span small clear spacing loess tunnel, systematic anchor bolt, support theory