Laminated rock beam design for tunnel support

D.A.F. Oliveira and L. Paramaguru

Abstract

The design and construction of semi flat-roofed tunnels, i.e. with a high arch radius to roof span ratio, using a voussoir beam analogy has been proven successful over time. In spite of such a success, the linear arch theory or voussoir beam analogy has always been subjected to a certain level of scepticism due to some of its perceived limitations. Some of the concerns are related to appropriate design methods for the design of rock bolting of multiple beds/laminations in cases where single laminations are deemed unstable upon excavation or while addressing some adverse conditions. This paper investigates the applicability of an analytical solution of the voussoir beam theory for the design of rock bolts in laminated rock beams which has been confirmed with numerical analysis using DEM (Distinct Element Method) analysis. The proposed analysis method can be easily implemented in a spreadsheet to provide rapid assessments though it is considered only one part of the design process with other potential instability mechanisms assessed using other analysis methods.