【摘要】 大跨度隧道断面尺寸大，施工步序多，其不可避免对隧道周围土体产生强烈的扰动，而对于小净距大跨度隧道而言，先后行洞施工的叠加作用将加剧土体的松动和变形。针对充分考虑地层和支护结构影响的沙浦山隧道大跨度小净距洞口段，采用FLAC三维数值模拟研究洞口段施工阶段的力学特征。结果表明：双洞开挖条件下围岩水平位移增长更为明显，中夹岩处水平位移出现峰值，尤其是两洞拱腰间围岩受较大的水平挤压作用，水平方向位移增长较大，中夹岩处水平位移显著易于产生拉伸破坏。大跨度小净距隧道先行洞开挖将引起围岩大范围扰动，使得后行洞施工条件变差，后行洞成为施工的薄弱环节。后行洞开挖扰动主要作用于先行洞拱腰和拱肩处，使得该处安全系数显著下降。更多还原

【Abstract】 The large-span tunnel has large section size and many construction steps, which inevitably produces strong disturbance to the soil around the tunnel.But for the large-span tunnel with small clean distance, the superposition effect of successive construction of two tunnel tubes will intensify the loosening and deformation of the soil.In this paper, the influence of stratum and support structure is fully considered for the Shapushan tunnel with large span and small clean distance at the entrance section.FLAC three-dimensional numerical simulation is used to obtain the mechanical characteristics of the entrance section at the construction stage.The results show that: Under the condition of double tunnel excavation, the horizontal displacement of surrounding rock increases more obviously, and the peak value appears at the middle interlayer.Especially, the horizontal displacement of surrounding rock between the arch and waist of the two tubes is greatly affected by horizontal compression, and the horizontal displacement of the middle interlayer is obviously prone to tensile failure.The excavation of the large span and small clear distance tunnel will cause a large range of disturbance to surrounding rock, which makes the construction conditions of the subsequent tunnel worse, and the subsequent tunnel becomes the weak link of the construction.The excavation disturbance mainly affects the waist and shoulder of the first constructed tunnel, which makes the safety factor decrease significantly.更多还原