大直径盾构隧道开挖面失稳极限平衡分析

Limit Equilibrium Analysis of the Face Instability in Large Diameter Shield Tunnels

近年来大直径隧道在国内外得到越来越多的应用,随之带来的开挖面稳定性问题也受到越来越多的关注,其关键是开挖面支护压力的大小。通过对三维楔形体模型进行修正并采用极限平衡分析方法,推导出适于大直径盾构隧道开挖面局部稳定性问题的理论计算公式。通过对理论公式的分析,存在楔形体最优破坏角及开挖面极限支护压力,分析了楔形体最优破坏角与局部失稳率、土体内摩擦角和隧道覆土厚度的关系,以及开挖面极限支护压力与土体内摩擦角和隧道覆土厚度的关系。

Large diameter shield tunnels are widely constructed in recent years. Tunnel face stability is one major concern for setting a proper support pressure. The traditional model of wedge for stability analysis of tunnel face is ex- tended to encompass large diameter tunnels on the partial face instability adopted by limit equilibrium methods. It is founded that thereis the optimal angle between the working face and the wedge and the limit support pressure. The rela- tionship between the optimal angle and ratio of partial face instability, soil internal friction angle, cover- depth ratio are demonstrated. The relationship between the limit support pressure and soil internal friction angle, cover- depth ratio are also shown. The results are compared with Anagnostou＇s solution and Leca＇s solution, which reveal that the results are suitable for the face stability of large tunnels.