地层倾角对浅埋偏压隧道拱顶沉降的影响研究

Research on the Influence of Formation Dip on the Vault Crown Settlement of Shallow Buried Bias Tunnel

借助FLAC3D有限差分软件,着重考虑地层倾角,结合现场量测,对重庆黔江蒲草沟Ⅴ级浅埋偏压隧道进行结构稳定性分析,探讨不同地层倾角下隧道的拱顶沉降特征。研究表明:所构建的数值模型对拱顶沉降的预测值与现场实测值变形规律基本吻合,且最大差值仅为0.87 mm,验证了本次数值模拟的正确性;随着砾岩夹砂岩层倾角增大,拱顶沉降呈加速增大趋势,开挖面处拱顶沉降变化率也显著提高;砾岩夹砂岩层倾角与地形一致导致的误差为16.4%,倾角为水平导致的误差为11.9%,误差均较大。由此可知,在砾岩夹砂岩层倾角变大的情况下,应提高隧道结构的强度,在数值计算中简化地层倾角会导致较大的计算误差。研究成果可推广应用于砾岩夹砂岩层的浅埋偏压隧道。

With the help of FLAC3 D finite difference software, the structural stability of the V-level shallow-buried bias tunnel at Pu Caogou Village of Qianjiang District of Chongqing is analyzed based on field measurement in consideration of the dip angle of the formation. The settlement characteristics of the tunnel with different dip angles are discussed. The research results show that the predicted value of the vault crown settlement is basically consistent with the deformation law of the field measurement and the maximum difference is only 0.87 mm, which verifies the correctness of the numerical simulation. With the increase of the dip angle of the conglomerate sandwiched sandstone layer, the vault crown settlement shows an accelerating trend, and the change rate of the vault crown settlement at the excavation surface is also improved significantly. The error is 16.4% in the assumption that the inclination of the conglomerate intercalated with sandstone formation is consistent with the terrain, and the error is 11.9% in the assumption that the formation is horizontal. Both errors are large. Therefore, when the dip angle of the conglomerate sandwiched sandstone layer becomes larger, the strength of the tunnel structure should be improved. Nevertheless, simplifying the dip angle of the formation in numerical calculation may lead to large calculation error. The research results can be applied to shallow-buried bias tunnel in the conglomerate sandwiched sandstone layer.