Study on creep mechanism of surrounding rock and mechanical response of surrounding rock-lining structure of diversion tunnel in active fault zone
In order to study the influence of fault dip angle on the creep mechanism of surrounding rock and the mechanical response of tunnel lining structure in diversion tunnel with active fault zone,the creep physical model test of tunnel lining structure passing through active fault under different fault dip angles is carried out.On the basis of the test results,the displacement mode of active faults,the circumferential strain and longitudinal strain of lining,and the change law of contact pressure between surrounding rock and lining under different fault dip angles are analyzed.The whole process of crack initiation→ expansion→failure of lining structure is observed.The results show that the displacement mode curves of the tunnel axis under different fault dip angles and different dislocation magnitudes are all S-shaped.And there is sliding between the staggered plate and the influence zone.This makes the discontinuous characteristics of the displacement mode curve in this interval obvious.The peak of the displacement gradient curve represents the speed of the displacement change.The rapid deflection area and the peak area of the curve also correspond to the serious damage area of the lining structure.The dislocation risk assessment index is defined by the displacement gradient.It is found that with the decrease of the dip angle of the active fault zone,the tunnel lining structure is more likely to be broken in the fracture zone and the damage degree is more serious.At the same time,with the decrease of the dip angle of the active fault zone,the high fault risk area gradually runs through the whole fracture zone area.Therefore,the fault risk assessment index can be used as a quantitative index to evaluate the severity of structural damage.In terms of the appearance damage of the tunnel,the lining located at the junction of the staggered plate and the upper influence zone is more likely to be broken.With the decrease of the dip angle of the active fault zone,the damage range of the lining structure and the ratio of the damage range to the hole diameter also gradually increase.When the fault dip angle is 90°,the ratio of the failure range to the hole diameter is 1.36.When the fault dip angle is 70°,the ratio of the failure range to the hole diameter is 1.88.When the fault dip angle is 60°,the ratio of the failure range to the hole diameter is 2.64.Therefore,the risk of the tunnel lining structure crossing the active fault zone vertically is the smallest.
rock mechanicsfault dip anglecreeping motiondisplacement modefracture zonerisk assessment indicators for mistakes
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