Method and model experiment of resisting dislocation of tunnel based on the brittle buffer concept
[Objective]Tunnels are integral to transport infrastructure and often face the formidable challenge of traversing active fault zones during construction.The active fault zones indicate potential geological disturbances,leading to structural damage and posing a severe threat to tunnel safety.Therefore,this study aims to propose a method of resisting dislocation of tunnel based on the brittle buffer concept to enhance the structural integrity of tunnels when confronted with displacements induced by fault activities.The method involves strategically filling the space between the primary and secondary linings with brittle and compressible materials,which serve as buffers to absorb and mitigate localized displacements caused by fault activities,thus protecting the tunnel from substantial damage.[Methods]To rigorously study and validate the effectiveness of the proposed brittle buffer structure in resisting fault displacements,a comprehensive indoor model experiment was designed and implemented.Scaling down the size according to a 40∶1 geometric similarity ratio and using similar materials for the surrounding rock,lining,and buffer structures,tunnel model was cast in the laboratory,simulating fault movements within the model box.The analysis focused on the deformations and failure characteristics of the models under different fault loads,confirming the effectiveness of the brittle buffer structure.[Results]Observations of tunnel deformation and failure modes after fault movements revealed distinct patterns.In the hanging wall of the fault,the brittle buffer structure at the arch top was crushed,accompanied by void formation at the arch bottom.Meanwhile,in the footwall of the fault,the arch top exhibited voiding,whereas the brittle buffer structure at the arch bottom was crushed.This deformation pattern effectively dispersed local shear deformations at the fault location,markedly mitigating damage to the lining.Impressively,under the protection of a 50-mm buffer structure,the lining model showed minimal damage even with a 100-mm displacement,equivalent to a substantial 4-m displacement in practical design scenarios,underscoring the robust performance of the brittle buffer structure in preserving the structural integrity of the tunnel.Furthermore,this study delved into strain monitoring data analysis and revealed a considerable shift in the peak strain of the lining away from the fault crush zone.This strategic relocation of strain concentrations to areas farther from the fault indicated a substantial reduction in strain intensity within the fault zone and confirmed the efficacy of the brittle buffer structure in dispersing and minimizing localized damage.[Conclusions]The results confirm the practical feasibility and effectiveness of incorporating a brittle buffer structure in tunnel designs for scenarios involving fault-induced displacements.This design exhibits exceptional performance in resisting fault-induced displacements,particularly suitable for tunnels crossing fault locations with significant estimated displacements.The outcomes of this study provide a crucial theoretical foundation and practical guidance for tunnel designs that cross active fault zones.This research contributes to the selection of antidisplacement solutions in tunnel engineering,paving the way for innovative approaches to address seismic challenges in tunnel construction.
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