Analysis on Action Mechanism of Multi-layer Support in Soft Rock Large Deformation Tunnels with Consideration of Rheological Effects
In order to better describe the rheological characteristics of surrounding rock under multi-layer support in soft rock tunnel with large deformation,the constitutive model of surrounding rock is assumed to be a viscoelastic-plastic rheological model,and the plastic yield criterion is selected as the Mohr-Coulomb yield criterion.The multi-layer support is simplified as applying different constant support forces at different times.The analytical solution of the displacement of surrounding rock under multi-layer support is derived.By comparing and analyzing with the finite difference numerical solution,it is concluded that the displacement of surrounding rock over time obtained by the two methods is basically consistent,verifying the rationality of the analytical solution.Through specific examples,the influence of multi-layer support on the stress field and displacement field of surrounding rock is analyzed.The research results show that:(1)The displacement of surrounding rock caused by the first-layer support force applied simultaneously with tunnel excavation is related to the viscoelastic-plastic effect of surrounding rock,and the incre-mental displacement caused by subsequently applied support forces is only related to the viscoelastic effect of sur-rounding rock;(2)With the increase of time and the increase of the support reaction force on the tunnel wall under multi-layer support,the tangential stress at the interface between the plastic zone and the viscoelastic zone of sur-rounding rock gradually decreases;(3)The radial displacement of surrounding rock shows a decreasing trend from the tunnel sidewall to the depth of surrounding rock,and increases with time until the deformation stabilizes.
Soft rock tunnel with large deformationRheological effectsMulti-layer supportSurrounding rock dis-placementSurrounding rock stress
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