| As the depth of mine mining gradually increases,difficult tunnel support becomes an inevitable problem in many mines.Due to the high stress environment associated with large mining depth,surrounding rock of many excavation tunnel enters the state of soft rock,which results in the characteristics of large deformation,rapid deformation and long time creep of the excavation tunnel within the service life.The deformation characteristics of the surrounding rock of highly stressed soft rock tunnel make it difficult to support the tunnel,and there is a high failure rate of bolt.As an important part of the tunnel support system,bolt support often breaks in some localized areas of the tunnel,causing instability of the entire tunnel.Therefore,the study of the mechanical behavior of supporting bolts in highly stressed soft rock tunnels is of great engineering significance for safeguarding mining safety.First of all,the paper analyzes the distribution characteristics of the stress field,the extension of the plastic zone and the deformation of the surrounding rock in the high stress soft rock tunnel through theoretical analysis and numerical calculation.,it is found that the anchor bolt in the support tunnel not only needs to carry the axial tensile effect,but also needs to carry the transverse shearing and bending effects.Based on the principle of Winkler foundation beam,the transverse force model of the anchor bolt was established.Combining with the axial load mechanical model of the anchor bolt,considering the forces in both axial and transverse directions of the anchor bolt,the highly stressed soft rock tunnel was analyzed theoretically.The research shows that: in highly stressed soft rock tunnel,the anchor bolts mainly carries the combined axial and transverse bending forces;the axial force of the anchor bolt stays almost constant near the tail part of the tray,and the axial force of the anchor bolt rapidly decreases at the end part deep inside the rock mass,and the bending moment of the anchor bolt is "Wave-shaped" distribution along the length of the bolt in both positive and negative directions of the axis,and the combined effect of axial tension and transverse bending of the anchor bolts is greater in a stress concentration area.According to Jinshandian iron mine support conditions,the FLAC3 D numerical analysis software was used to study the mechanical behavior of full-length anchored GFRP anchor bolts in highly stressed soft rock tunnel.The research shows that: the stress on the anchor bolts at different installation positions in the same section tunnel is quite different.The tunnel domes and the two gang bolts are mainly subjected to the axial tensile load,and the arches and the anchor bolts at the bottom corners are axially stretched at the same time.And lateral bending loads,and the bending moments of the bolts at the shoulder and bottom corners of the tunnel are mainly concentrated on the outer end of the bolt near the pallet position;the bending moments of the bolts in the spandrel and shoulder angles of the tunnel mainly occur in the initial period of support,with Support time increased and gradually decreased.The numerical calculation results verify the theoretical analysis results well,so it shows that the established stress calculation model of bolts in highly stressed soft rock tunnel can reflect the stress characteristics of the bolt.Finally,based on the above research results,the integrated roadway support measures of metal-non-metallic anchor rod combined support and grouting reinforcement are put forward for the bolt support of soft and broken mine rock in Jinshandian iron mine.The research results provided the theoretical basis for the bolt support design and parameter optimization in highly stressed soft rock tunnel,which can effectively improve the reliability of bolt support of in highly stressed soft rock tunnel. |
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