某基坑支护方案对相邻地铁区间的影响分析

城市地下空间的发展经常会遇到基坑开挖影响地铁隧道安全的难题。本文结合工程实例,建立弹塑性土体-围护结构有限元计算模型,对两个基坑方案中邻近盾构区间隧道变形、隧道内力变化进行分析。结果表明:(1)地铁周边深基坑开挖对区间隧道影响与众多因素有关,属于较为复杂的土力学行为,因此,在设计阶段应对设计方案加以比选并进行有效地分析,以减小施工过程中对隧道的影响;(2)基坑与隧道的相对距离越大,基坑开挖对隧道影响越小。基坑支护结构水平位移最大值并不出现在坑底,而是坑底下一定范围内;(3)靠近地铁侧基坑需加强支撑,并需在基坑与隧道之间增加测斜监测。

Influence of Foundation Pit Supporting Scheme on Adjacent Existing Subway Tunnel

With the expansion of city and rapid development of rail transit, the tunnel safety may be affected by the construction of adjacent foundation pit project. Combined with the actual engineering work, the elastic-plasticity constitutive model is used in this paper for numerical analysis, and the variation of stress and deformation for the tunnel of two foundation pit excavation schemes are discussed, which is induced by adjacent railway tunnel construction. It shows that: 1. the foundation pit excavation adjacent to metro has influence on the tunnel and an effective analysis is necessary during design stage to minimize its affection on metro tunnel; 2. the negative influence of foundation pit excavation on the tunnel can get smaller by increasing the relative distance between the foundation pit and tunnel. The lateral displacement appears not at the pit bottom but lower than it; 3. the strut in foundation pit close to subway side should be strengthened, and the inclination monitoring between foundation pit and subway is necessary.