Dynamic superposition of tri-anchor support technology at tunnel junction under complex rock strata

A large area of roof falling occurs at the workingface, hampering the advancing of working face. The irrationality of first support in previous construction causes the concrete lining to produce some cracks after permanent support and the convergence (reduction of cross-section) occurs, which influences the natural usage of the tunnels and laneways heavily. A lot of steel brackets and timbers are used in the reinforcement of distorted laneways. However, most of these linings generally affect the tunnel or laneway’s natural usage in the later stage (see Figure 2). These existing problems own to two aspects. One is that the rock bolt or timber lining support can’t close off the surrounding rock and prevent the interaction between air and rock mass such as rock softness, argillation and dilatability.