泥质粉砂岩隧道变形及长期稳定性研究

以广东省惠清高速太和洞隧道工程为依托,通过室内试验和数值模拟,对典型软岩隧道大变形问题进行了研究。首先通过FLAC3D数值模拟软件对隧道开挖阶段的受力特征、施工变形进行计算;其次考虑了流变效应,通过单轴压缩流变试验得到泥质粉砂岩的应变-时间曲线,选取伯格斯黏弹性模型拟合出相关流变参数并运用于隧道长期变形的模拟计算中,对隧道运营期稳定性做出了评价。研究结果表明:(1)泥质粉砂岩具有明显的蠕变特性,在270 kPa左右的应力水平下进入非稳定蠕变阶段;(2)伯格斯黏弹性模型能够较好地描述泥质粉砂岩的流变特性;(3)隧道开挖阶段拱顶、拱底处有明显的应力释放,拱脚处有应力集中现象,右洞支护结构对围岩稳定性的提升,使左洞开挖阶段围岩的受力状态、变形情况均优于右洞;(4)隧道在运营期7年以前表现出较明显的蠕变特性,7年之后进入稳定阶段。

Study on Deformation and Secular Stability of Argillaceous Siltstoue Tunnel

The paper analysed the large deformation issues of typical soft rock tunnel through the project of Taihedong tunnel, Guangdong province, through indoor test and numerical simulation method. Firstly, the numerical simulation was used to calculate the construction deformation and the stress characteristics of tunnel excavation process by FLAC 3D. Taking the rheological properties of weathered argillaceous siltstone into consideration, the strain-time curve of argillaceous siltstone was obtained through uniaxial compression rheological test. Based on the burgess rheological model, the rheological parameters and equations were obtained. The parameters were applied in the calculation of long-term deformation of the tunnel, with the stability of the tunnel during operation evaluated. Research results prove that: (1) argillaceous siltstone performs the typical creep properties, which enters the unsteady creep stage when the stress reached 270 kPa; (2) Burgers viscoelastic model could demonstrate the argillaceous siltstone rheological behaviour effectively; (3) significant stress release is performed at the top and bottom of arch during tunnel excavation. The stress concentration occurred at the arch foot. The stability of surrounding rock is improved by the support structure of the right tunnel, leading to the superior of stress state and tunnel deformation of the left tunnel; (4) there will be obvious creep behaviour at the early stage of tunnel operation period, which would stabilized after 7 years.