An improved numerical simulation approach for arch-bolt supported tunnels with large deformation

摘要

Our goal was to develop an effective research tool for tunnels with significant deformations supported by arch-bolt union system. The improved numerical simulation approach is constructed through additional development of FLAC(3D). There are four parts that form the approach: a yieldable supporting arch module, a separable arch-rock interaction module, a breakable anchor bolt module, and a practicable surrounding rock module. The yield criterion of the supporting arch was proposed and embedded in the modified beam element via the FISH language programming. A separation criterion is proposed for the arch-rock interaction link, and the separable arch-rock interaction module is realized through modifying the normal-yield attachments of the built-in arch-rock links. A tensile breakage failure criterion is proposed for the anchor bolt using the ultimate elongation ratio delta(f) of the whole anchor-free part as the criterion. Taking an actual mining roadway tunnel as the simulation object, two simulation schemes adopting the newly improved approach and the original method were carried out respectively, and comparisons of the results show that: (1) the bending moment and axial force at the yielding moment of the compression-bending element change from independent to related after modification, and the computed deviation of the arch model caused by the shortcomings of the original beam element were effectively suppressed; (2) the separable link is proved effective by the supporting forces curves and arch deformation responses; (3) the breaking property of the anchor bolt is implemented, and the response is sensitive; and (4) the surrounding rock controlling results in the modified model scheme are closer to the actual. The analysis shows that the improved numerical simulation approach is much more reliable for large deformation tunnel behavior with arch-bolt union support, especially concerning the bearing and failure behaviors of the supporting arch and anchor bolt.