Development and application of a model test device for active fault tunnels crossing complex fault under high in-situ stress environment
When active faults experience tectonic movements,tunnels crossing these active faults will undergo varying degrees of structural damage and failure.Existing experimental setups that simulate the fault displacement of tunnels crossing active faults are mostly designed for shallow-buried tunnels and do not consider deep-seated stress conditions.This limitation has impacted the applicability of their test results to deep-buried,high-stress tunnel projects.Given this,the development of an experimental apparatus capable of simulating complex fault-displacement mechanisms under high in-situ stress conditions becomes a crucial component.This study,in conjunction with the characteristics of large lifeline projects crossing active faults in the strong seismic zone of western China,determined the parameters required for the experimental apparatus.We have successfully developed this apparatus and utilized it to investigate the differences in lining damage characteristics between deep-buried and shallow-buried tunnels.The results show that:(1)tunnel structures crossing active fault zones in the strong seismic regions of western China exhibit features such as significant burial depth,high in-situ stress,and complex fault displacement.Consequently,the design parameters for the experimental apparatus were determined,including a confinement pressure of 0.8 MPa,a horizontal fault offset of 20 cm,and a vertical fault offset of 10 cm.(2)By conducting free-field and tunnel model fault-displacement experiments,it was confirmed that the equipment can effectively simulate pure strike-slip,dip-slip,and strike-slip/dip-slip-coupled fault movements.Moreover,it was observed that the confining pressure remains stable during the fault movement process,thereby achieving the objectives of this research and equipment development.(3)The tunnel fault-displacement tests yielded the following outcomes:Deep-buried tunnels exhibited significant compressive deformation,resulting in larger areas of damage.Shallow-buried tunnels,on the other hand,experienced shearing at the fault zone,leading to more severe structural damage.Moreover,when the fault was oriented at a small angle to the tunnel axis,the level of damage to the tunnel increased.The development of this equipment provides a crucial foundation for investigating the impact of complex fault mechanisms on tunnels crossing active faults in high-stress environments.
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