Sensitivity Analysis of Influencing Factors of Karst Tunnel Construction Based on Orthogonal Tests and a Random Forest Algorithm

Abstract

To conduct a sensitivity analysis of the relevant parameters that impact the mechanics of tunnel construction in karst areas, firstly, the orthogonal design and range analysis method is applied to sort the 11 kinds of karst-tunnel-influencing factors from high to low according to the sensitivity degree. Secondly, the random forest algorithm based on an orthogonal experimental design is applied to the feature importance ranking of the influencing factors of karst tunnels. Thirdly, according to the results of the sensitivity analysis, the optimum combinations of influencing factors of tunnel construction in karst areas is obtained. The research based on these two methods shows that when taking the vertical displacement as the target variable, the parameters with the highest feature importance are A6 (tunnel diameter) and A10 (tunnel buried depth). When taking the first principal stress as the target variable, the most important influencing factors are A10 (tunnel buried depth) and A9 (location of karst cave). When taking the principal stress difference as the target variable, the most important influencing factors are A10 (tunnel buried depth) and A6 (tunnel diameter). The level combination of the 11 influencing factors obtained by taking the principal stress difference as the target variable was more balanced than the vertical displacement and the principal stress difference as the target variables. The results of this study will provide a theoretical basis to study key parameters in the response of mechanical characteristics to the safe construction of tunnels in karst areas.

A Calculation Method for Reliability Index of a Deep–Bedded Karst Tunnel Construction with Cavity Located Ahead of Tunnel Working Face

“…The external power of each block in this karst deep tunnel construction model under self-weight is obtained by multiplying the area of the block with its self-weight. In Figure 2a,b, the expression W ex−1−1 of the external power of the triangle masses D a,0 D a,1 D ′ a,1 , D a,0 D a,m F a,0 and D a,0 D ′ a,m−1 F a,1 at their self-weight is presented by expression (31).…”

“…Thirdly, the analytical solution for calculating the probability of failure and the reliability index of karst tunnel engineering with cavities located ahead of the tunnel working surface could be applied to practical engineering. The study could analyze the quantitative assessment of the influencing factors [31] on the construction safety and reliability of these deeply buried karst tunnels.…”