接触面粗糙度对软岩隧道锚渐进破坏特征的影响研究

Influence of the interface roughness on the progressive failure characteristics of tunnel-type anchorage in soft rock

为了研究接触面的粗糙度对软岩隧道锚渐进破坏特征的影响,通过制作3组不同粗糙度接触面的软岩隧道锚相似模型,结合数字图像相关技术,系统地对比分析不同粗糙度接触面的软岩隧道锚承载过程中岩体裂纹的发展规律和空间分布特征,结果表明:隧道锚的极限承载力随接触面粗糙度的降低而逐渐降低。随接触面粗糙度的降低,围岩裂纹的萌生角度逐渐增大,拱顶围岩中的主裂纹位置从后锚面起逐渐向拱顶中前部转移,围岩由整体破坏转变为以拱顶中前部局部围岩的破坏为主;拱底围岩中的裂纹则从贯通至地表且近似平行于锚体轴向的剪裂纹转变为零星的大角度短小裂纹,锚塞体下部也由薄层剪切带破坏模式转变为沿接触面滑移的破坏模式。在接触面粗糙度下降过程中,软岩隧道锚的破坏顺序由“拱顶后端岩体压剪(或拉剪)破坏→接触面滑移、脱黏→中前端岩体拉剪与拉伸破”转变为“接触面滑移、脱黏→拱顶前端岩体拉剪破坏→拱顶后端岩体拉伸破坏”。该研究成果可为揭示隧道锚的工作性状和破坏机制、完善相关设计计算理论提供基础依据。

To investigate the influence of the roughness of the interface on the progressive failure characteristics of tunnel-type anchorage(TTA)in soft rock,three similar models of TTAs with different interface roughnesses were made,and the digital image correlation technology was employed simultaneously to systematically compare and analyse the propagation and spatial distribution characteristics of cracks during progressive failure of TTAs.The results indicate that the ultimate bearing capacity of the TTA decreases gradually with the decrease of the roughness of the interface.Furthermore,the initiation angle of the crack in the surrounding rock increases gradually with the decrease of the roughness of the interface.Simultaneously,the initiation location of the main crack in the surrounding rock of the upper part of the plug body also gradually moves to the middle and front end of the crown of the plug body.The surrounding rock in the upper part of the plug body changed from the overall failure to the local failure.The failure range of surrounding rock is concentrated in the middle and front part of the crown.The cracks near the floor of the plug body gradually change from shear cracks into sporadic large-angle short cracks.The shear cracks are approximately parallel to the axis of the plug body and penetrate to the ground surface.The failure mode of the lower part of the plug body changed from a thin shear zone to slip along the interface.With the decrease of interface roughness,the failure sequence of the TTA changes from“compressive-shear(or tensile-shear)failure of rock mass at the back end of the crown→slip and debonding of interface→tensile-shear and tensile failure of rock mass at the middle front end of the crown”to“slip and debonding of interface→tensile-shear failure of rock mass at the front end of the crown→tensile failure of rock mass at the back end of the crown”.The research results can provide a basis for revealing the working characteristics and failure mechanism of TTAs and improving the design calculation theory.