Stress Response of Red Mudstone Tunnel Crossing Water-rich Fault
To explore the stress state of lining structures in a tunnel traversing a water-rich fault zone,the long-term in-situ stress monitoring of surrounding rock,initial steel arch frames,and secondary lining concrete were conducted in a red-bed mudstone section of a tunnel under construction in Gansu.The force patterns of the tunnel structure were analyzed during the water and mud outburst control period in the water-rich fault.The results show that moisture seepage from the water-rich fault results in a maximum surrounding rock pressure of 498.28 kPa on the crown during construction.Following the application of the secondary lining,the pressure decreases gradually,but the pressure on the inverted arch continues to rise,reaching a peak of 352.75 kPa.The initial steel arch supports display a clear asymmetrical force distribution,with greater force on the upper outer side than the lower.Maximum compressive stress occurs at the crown and right waist,where the right waist experiences bending and breakage due to stress from fault activity.Inside the arch,stress distribution is lower at the top and higher at the bottom,with the greatest compressive stress on the left side of the inverted arch.Overall,the secondary lining concretes comply with the safety factor requirements of tunnel.The crown and right waist,being directly impacted by the water-rich fault,sustain the maximum concrete compressive stress.Continuous moisture penetration from the fault zone to the tunnel's base rock post-construction prolong the stress stabilization period for the inverted arch,increasing the risk of floor heave during long-term operation.It is crucial to monitor the deformation of the tunnel base during operation.These results offer valuable insights for optimizing reinforcement strategies and formulating drainage plans in similar tunnel projects.
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