Safety Study On Ultra-Shallow Expressway Tunnel And Its Construction Process In Unfavorable Surrounding Rock

Calculation of rock pressure applied to an ultra-shallow depth tunnel has been analyzed in terms of key block theory, and its mathematical formula is also established according to a mechanical model set up in the paper. The tunnel is subject to asymmetric load caused by oblique topography. The safety of the ultra-shallow expressway tunnel in strata with oblique geomorphology is also dissected and affected by rock strength and tunnel support. Steel pipe grouting from ground surface is used to consolidate the unfavorable surrounding rock before excavation, concurrently the reinforcing scope and tunneling procedure are proposed according to the analysis of the asymmetric load induced by tunnel excavation in poor surrounding rock with inclined topography.