【摘要】 隧道由小断面扩挖为大断面的过程中，围岩的扩挖响应较为复杂，容易产生应力集中，需要对扩挖过程中围岩的应力、位移及地表沉降进行分析。以厦门疏港通道蔡尖尾山2#隧道为例，采用ANSYS软件分析了超大断面小净距隧道断面加宽尺寸分别为0.5 m、2.75 m、3.5 m、3.1 m时围岩的力学特性，并提出了控制对策。结果表明：隧道的拱顶、底板和地表沉降和隧道的扩挖宽度呈线性关系；隧道拱顶和地表沉降随着扩挖宽度的增加而增加，而扩挖侧隧道底板的沉降却呈现出减小的趋势；小净距隧道中，扩挖施工对扩挖侧隧道围岩位移和应力的影响要明显大于对另一侧隧道的影响；超大断面小净距隧道扩挖优化方案可采用双侧壁导坑法由小断面渐变过渡至大断面扩挖的方法。更多还原

【Abstract】 In the process of tunnel expansion construction from small section to large section, the response of surrounding rock to the expansion construction is complex, which is easy to produce stress concentration.It is necessary to analyze the stress, displacement and surface settlement of surrounding rock in the process of expansion construction.Taking Caijianweishan 2# tunnel of Xiamen Shugang Channel project as an example, the mechanical properties of surrounding rocks in super large section tunnels with small clear distance are analyzed by using ANSYS software when the section widening dimensions are 0.5 m, 2.75 m, 3.1 m and 3.5 m respectively, and the control countermeasures are put forward.The results show that there is a linear relationship between the settlement of vault, floor and surface and the expansion width.The settlements of tunnel vault and surface increase with the increase of expansion width, while the settlement of tunnel floor on expansion side decreases.For the tunnels with small clear distance, the influence of expansion excavation on the displacement and stress of the expanded tunnel is obviously greater than that of the tunnel on the other side.The double side drift method can be used to gradually transit the tunnel from small section to large section, which can optimize the expansion scheme of large section tunnels with small clear distance.更多还原