双圆盾构隧道施工对平行既有隧道的影响分析

对双圆（DOT）盾构隧道周围土体采用椭圆形非等量径向位移模式，在镜像法基本原理上，推导土体损失引起的附加应力计算公式，研究双圆盾构正面附加推力、双圆盾构机与土体之间的摩擦力以及土体损失在平行既有隧道上引起的总的附加荷载的分布规律。研究结果表明，附加荷载的变化规律与双圆盾构机和邻近平行隧道的相对位置密切相关，是一个三维问题；随着双圆盾构机开挖面通过前后，附加荷载由压力变为拉力；土体损失是引起相邻隧道上附加荷载的主要因素，其次分别是盾壳摩擦力和正面附加推力；已建隧道受到的附加荷载变化规律与其和双圆盾构机的净距 S 密切相关，随着 S 的减 小，附加荷载急剧增大；随着平行既有隧道轴线埋深的变化，在轴线位置处，双圆盾构机对平行既有隧道的附加荷载影响最大。

Analysis of influence of DOT shield tunneling on existed adjacent tunnel

Based on the method of images, the three-dimensional soil loss additional load formula caused by DOT shield tunneling soil loss is derived by using non-uniform soil movement model. The distribution regularity of total additive load from additive thrust force, the friction between DOT shield machine and soil together with soil loss on existed adjacent tunnel is researched. The results show that: the distribution regularity of additive load is closely related with the relative position of existed adjacent tunnel and DOT shield tunnel; and it is a three-dimensional problem. In the thrust direction, the additive stress changes from tension behind into pression ahead of the excavation face. Soil loss is the main factor in total additional load, followed by friction and thrust additional force; the additional load that the existed adjacent tunnel subjected to is closely related to its net spacing away from DOT shield machine S; and additional load increases rapidly when S decreases; the existed adjacent tunnel is subjected to the greatest additional load in the axis position of DOT shield machine with the variation of axis buried depth of the existed adjacent tunnel.