Three-Dimensional Stratigraphic Reconstruction Based on Improved Coupled Markov Chain

Tunneling projects frequently encounter intricate geological conditions during excavation. A comprehensive understanding of subsurface geology is imperative for tunnel design. This research introduces a novel shield tunneling construction simulation methodology within a three-dimensional (3D) geological model based on an improved coupled Markov chain. The improved Markov chain method enhances the alignment of the predictive output with the probable stratigraphic distribution. This study marries engineering geological survey data with the shield tunneling excavation simulation. To establish a congruent relationship between the regular grids of the geological model and the irregular grids of the numerical model, an asymmetric grid 3D mapping technique is proposed. The development degree of unfavorable weak interlayers impacting tunnel construction is evaluated through the defined exceedance probability. In light of these premises, the simulation methodology is applied to the detailed modeling of a large-diameter undersea tunnel in Qingdao. Based on the most unfavorable weak interlayer development scenario, the safety performance of a 3D shield tunnel traversing this stratum is analyzed using numerical simulation methods. The promising potential of the proposed methodology for tunnel excavation simulations under geological uncertainty is validated. The approach offers an innovative contribution to the field, enhancing tunneling predictability, risk management, and overall construction efficiency.