软弱破碎地层偏压小净距隧道群施工力学响应研究

Study on the Mechanical Response of Biased Neighborhood Tunnel Group Construction in the Soft and Weak Surrounding Rocks

软弱围岩条件下,偏压小净距隧道群施工极易诱发围岩失稳,造成施工安全事故。以大山隧道工程为依托,基于有限元分析软件ABAQUS建立数值模型,研究地层条件、隧道净距以及隧道埋深等因素对软弱围岩条件下偏压小净距隧道群施工的影响,分析施工诱发的围岩变形规律及其受力特点。研究表明:由于地层偏压的影响,小净距隧道施工引起的围岩变形规律具有显著的非对称性特点;在竖向位移和水平位移叠加的情况下,左右两侧机动车隧道顶部呈现更大范围W形沉降槽;围岩条件越差,隧道埋深越小,净距越小,隧道施工诱发的围岩变形越大;围岩的力学性质直接影响衬砌结构的受力状态,靠近中夹岩处的衬砌结构受力状态更不利。

The construction of tunnels with small clearances in soft ground is prone to induce instability in the surrounding rocks,resulting in construction safety incidents.Based on the Dashan Tunnel Project,the research establishes a numerical model using ABAQUS to study the influence of ground conditions,tunnel clearances and tunnel burial depth on the construction of tunnel groups with a small clearance in soft and weak surrounding rocks,based on which the construction-induced surrounding rock deformation and mechanical characteristics are also analyzed.The study shows that:the deformation pattern of the surrounding rock induced by the construction of neighborhood tunnels has a significant asymmetric characteristic due to the stratigraphic bias.With the superposition of vertical and horizontal displacements,the top of the left and right motorway tunnels show a larger W-shaped settlement trough.The poorer the rock conditions,the smaller the tunnel depth and the smaller the spacing will result in greater construction-induced deformation of the surrounding rock.The mechanical properties of the surrounding rock directly affect the stress state of the lining structure,and the stress state of the lining structure near the middle sandwich rock is more unfavorable.