Methods for calculating rock pressure of symmetrical multi-arch deep tunnels

The mechanical characteristics of asymmetrical multi-arch tunnels are as follows: a symmetric geometry and structure form, large excavation span, various construction processes and complex structural stress. Therefore in the design of supporting structures, the load-structure model is usually used, and till now there aren't any mature methods for estimating the load. In this context, the conditions of asymmetric geometry and structure form of two cavities of a tunnel are considered. Based on the assumption of the double collapsed arches of multi-arch tunnels and according to the Protodyakonov's theory, a formula for calculating the rock pressure under deep buried conditions is derived. Under symmetrical conditions, the derived formula becomes the conventional formula for multi-arch tunnels, which has proved the validity of the derived formula. The research methods and conclusions may provide an important reference for the determination of the design load of asymmetrical multi-arch tunnels.