不同大变形等级的层状软岩隧道施工模型试验与数值模拟研究

Study on model test and numerical simulation of layered soft rock tunnel construction with different large deformation grades

为探究复杂艰险山区层状软岩隧道非对称破坏特征,提出不同大变形等级下层状软岩隧道的合理施工变形控制技术,以九绵高速公路典型层状软岩隧道为工程背景,建立针对复杂艰险山区层状软岩隧道的大变形等级划分标准,在此基础上通过模型试验和数值模拟,就不同大变形等级下施工工法和支护方式对层状软岩隧道力学行为的影响开展系列研究。研究结果表明:在应力场–层理方向耦合影响下,层状软岩隧道受力与变形空间非对称分布最不利位置位于层理面法向或切向位置,并随着大变形等级(轻微、中等和强烈)的增大,隧道非对称力学特征越明显;此外,施工工法和支护方式对不同大变形等级的层状软岩隧道变形与受力改善效果存在差异,故针对3种大变形等级的层状软岩隧道,分别提出二台阶施工+单层初支+短锚杆支护、三台阶施工+单层初支+长短锚杆支护、三台阶预留核心土施工+双层初支+长短锚杆支护的建议施工变形控制技术。

To explore the asymmetric failure characteristics of layered soft rock tunnels in complex and difficult mountainous areas,and to propose reasonable construction deformation control technologies for layered soft rock tunnels under different large deformation grades,by taking a typical layered soft rock tunnel of Jiuzhaigou—Mianyang expressway,a large deformation grade classification standard for layered soft rock tunnels in complex and difficult mountainous areas was established as the engineering background.Then a series of studies were conducted on the influence of construction methods and support patterns on the mechanical behavior of layered soft rock tunnels under different large deformation grades through model tests and numerical simulations.The research results indicate that the most unfavorable position for the spatial asymmetric distribution of stress and deformation in layered soft rock tunnels is located in the normal or tangential position of the bedding plane due to the coupling effect of stress field and soft bedding direction,and the asymmetric mechanical characteristics of the tunnel become more obvious with the increase of large deformation grade(slight,medium and strong).Additionally,there are differences in the improvement effects of construction methods and support patterns on the deformation and stress of layered soft rock tunnels under different large deformation grades.Therefore,for three types of layered soft rock tunnels with large deformation grades,the recommended construction deformation control technologies for twostep construction+single-layer primary support+short rock bolt support,three-step construction+single-layer primary support+long and short rock bolt support,and three-step reserved core soil construction+double-layer primary support+long and short rock bolt support were proposed separately.