“…In this study, a X-ray CT imaging method was employed by leveraging these particular properties of KI solution to visualize the non-uniform flow formed during the percolation column test. As reported in an existing study, the concentration of the KI solution was 15 wt% ( Watanabe et al., 2019 ). Figure 3 Method to visualize non-uniform flow formed in column.…”
“…In this study, a X-ray CT imaging method was employed by leveraging these particular properties of KI solution to visualize the non-uniform flow formed during the percolation column test. As reported in an existing study, the concentration of the KI solution was 15 wt% ( Watanabe et al., 2019 ). Figure 3 Method to visualize non-uniform flow formed in column.…”
“…Fracture intensity was input on a per facies basis using a P 10 = number of fractures/length of scanlines = N/L*[L -1 ] ( Mauldon et al, 2000). P 10 measures abundance in a specified orientation, and so is converted into a direction independent P 32 , equivalent to fracture area per unit volume (P 32 =C 31 P 10 ; Mouldon et al, 2000;Wang et al, 2005). Consequently, the number of fractures measured in the field was dependent upon the orientation of the scanline, such that only fractures perpendicular to the scanline were sampled.…”
“…This phenomenon is particularly pronounced when tunneling activities intersect with deeply buried, weak rock layers rich in expansive clay minerals. The process of excavation in these scenarios triggers a rapid release of stored energy within the original rock matrix, yielding a dual effect: a redistribution of stress within the surrounding rock mass that leads to alterations in its state and the induction of a swelling effect [8][9][10][11] and the emergence of unloading surfaces that facilitate the development and extension of expansion strain.…”
This study investigates the dynamics of moisture absorption and swelling in soft rock during tunnel excavation, emphasizing the response to support resistance. Utilizing COMSOL numerical simulations, we conduct a comparative analysis of various strength criteria and non-associated flow rules. The results demonstrate that the Mohr–Coulomb criterion combined with the Drucker–Prager model under compressive loads imposes stricter limitations on water absorption and expansion than when paired with the Drucker–Prager model under tensile loads. Restricted rock expansion leads to decreased horizontal displacement and ground uplift, increased displacement in the tunnel’s bottom arch, and significantly reduced displacement in the top arch. The study also considers the effects of shear dilation, burial depth, and support resistance on the stress and displacement of the surrounding rock. Increased shear dilation angles correlate with greater rock expansion, resulting in increased horizontal displacement and ground uplift. The research study concludes that support resistance is critical in limiting the movement of the tunnel’s bottom arch and impacting the stability of the surrounding rock. Additionally, the extent of rock damage during the excavation of expansive soft rock tunnels is found to be minimal. Overall, this study provides valuable insights into the processes of soft rock tunnel excavation and contributes to the development of more efficient support systems.
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