Numerical Analysis of the Influence of New Shield Tunnel Excavation on Existing Shield Tunnels under Different Soil Conditions

为探究不同土性条件下新建盾构隧道施工对既有盾构隧道的影响，本文采用数值模拟方法，选取黏土与砂土两种典型土层作为研究对象，构建了新建盾构隧道开挖过程中对既有隧道影响的三维数值模型。通过对比分析两类土性条件下的既有隧道结构拱顶沉降、拱底沉降及地表沉降变形，揭示了土层类型对施工影响程度的差异性，并提出相应的风险控制措施。研究结果表明：土层性质对盾构施工引起的地表沉降与隧道结构沉降有显著影响，其中黏土条件下的地表沉降、拱顶沉降与拱底沉降均明显大于砂土条件，且沉降影响范围更广、持续时间更长，施工扰动对既有隧道结构的影响更为显著。该结论对类似工程中不同地质条件下的施工方案优化与风险控制具有重要指导意义。To investigate the impact of new shield tunnel construction on existing shield tunnels under different soil conditions, this study employs numerical simulation methods. Two typical soil types—clay and sand—were selected as the research objects. Three-dimensional numerical models were established to simulate the influence of new tunnel excavation on existing tunnels. Through comparative analysis of the deformation characteristics of existing tunnel structures—including vault settlement, invert settlement, and ground surface settlement—under these two soil conditions, the study reveals the differential influence of soil type on construction effects. Corresponding risk control measures are proposed. The results demonstrate that soil properties significantly affect ground surface settlement and tunnel structural settlement induced by shield tunneling. Specifically, under clay conditions, ground surface settlement, vault settlement, and invert settlement are significantly greater than those under sandy conditions. Moreover, the settlement extent is larger, the duration is longer, and the construction disturbance exerts a more pronounced impact on existing tunnel structures in clay. These findings provide important guidance for optimizing construction schemes and implementing risk control in similar projects under varying geological conditions.