顺层偏压挤压性软岩隧道让压预留变形角支护技术研究

Yielding Support Technology With a Reserved Deformable Angle for Squeezing Soft Rock Tunnels in Layered Biased Strata

针对顺层偏压挤压性软岩隧道的非均匀大变形问题,提出一种基于钢拱架预留变形角的新型让压单元。基于三维精细化建模分析顺层偏压荷载下让压预留变形角支护的承载特性和效果,并应用于中老铁路甘庄隧道,验证新型让压预留变形角支护技术的可行性。研究结果表明:1)顺层偏压荷载下隧道支护结构以弯曲变形为主,传统让压柔性节点在弯矩内力作用下易发生受拉破坏,让压预留变形角能有效释放拱架的弯矩内力,适应更大的弯曲变形;2)顺层偏压荷载作用下,采用让压预留变形角的钢拱架整体应力水平明显降低,拱架整体的承载能力满足强度要求;3)工程现场采用局部扩挖和设置钢拱架让压预留变形角后,隧道变形在断面开挖18 d以后控制在允许范围内,初期支护的应力集中现象减弱,钢拱架主体不再发生弯曲破坏。

Squeezing deformation of soft rock tunnels in layered biased strata is typically large and uneven.Therefore,a novel yielding element based on a reserved deformable angle is proposed.A three-dimensional detailed numerical model is built to analyze the bearing characteristics and the support effect of the yielding element under bias loading.To validate the feasibility of the model,it is applied in the formation of the Ganzhuang tunnel of the China-Laos railway.The research results show the following:(1)The deformation in the tunnel support under bias loading is dominated by bending deformation.The traditional yielding element is prone to tensile damage under the action of the bending moment.The yielding element with the reserved deformable angle can effectively release the bending moment of the steel arch and adapt to larger bending deformation.(2)Under bias loading,the overall stress level of the steel arch with the yielding element is significantly reduced,and the bearing capacity of the arch meets the strength requirements.(3)The field application shows that after installation of the novel yield element,tunnel deformation is controlled within the permissible range after 18 days of excavation;the stress concentration of the primary support is less pronounced,and the steel arch is no longer damaged by bending.