考虑环间接头影响的盾构隧道纵向变形简化解

Simplified solutions for longitudinal deformation of shield tunnels considering influences of circumferential joints

为反映外荷载下盾构隧道相邻环间张开和错台,提出考虑环间接头影响的盾构隧道纵向变形简化解答。首先,引入纵向梁-弹簧模型模拟盾构隧道纵向受力变形,其中采用Timoshenko短梁考虑隧道环段变形,引入转动和剪切弹簧分别模拟环间接头转动与错台。其次,构建弹性地基上纵向梁-弹簧模型的有限差分方程,以解决环间接头-管环非连续变形求解问题,并推导外荷载下既有盾构隧道的纵向变形公式。最后,建立新建隧道上穿和下穿引起既有盾构隧道的纵向变形解答,并与新建隧道上、下穿越工程案例及现有理论方法对比验证。研究结果表明:所提方法预测的隧道位移与Timoshenko连续梁模型,协同变形模型和实测数据均具有较好的一致性,但所提方法得到的环间错台略低于Timoshenko梁模型和协同变形模型;所提方法可考虑环间接头的影响,得到的隧道位移曲线呈现既不光滑也不连续的特征,其中环段变形以刚体位移为主,而环间接头主要发生转动和错台;而基于现有理论所得盾构隧道纵向位移均为连续曲线,无法反映环间接头的真实转动与错台位移。

In order to reflect the opening and dislocation between adjacent rings of a shield tunnel subjected to external loads,an analytical solution for the longitudinal deformation of the shield tunnel is proposed which considering the effects of circumferential joints.Firstly,a simplified longitudinal beam-spring shield tunnel model is introduced to simulate the longitudinal deformation of the shield tunnel.The Timoshenko short beam is used to consider the deformation of the segmental ring.The rotation and shearing springs are used to simulate the rotation and dislocation of the circumferential joints,respectively.Secondly,the finite difference equation of the longitudinal beam-spring model resting on the elastic foundation is established to solve the discontinuous deformation of the circumferential joint-segmental ring.The formula for the longitudinal deformation of the existing shield tunnel under external loads is further derived.Finally,the solutions for the longitudinal deformation of the existing shield tunnel associated with overcrossing tunneling and undercrossing tunneling are established,respectively.The proposed method is verified with new tunnel over-crossing and under-crossing case histories and previous theoretical methods.The results show that the predicted results by the present solution are consistent with those by the Timoshenko continuous beam model and cooperative deformation model and the field measurements,but the dislocations obtained by the present solution are slightly lower than those by the Timoshenko continuous beam model and the cooperative deformation model.The proposed method takes the effects of the circumferential joints into consideration,and it leads to the predicted displacement curve of the tunnel,which is neither smooth nor continuous.It is found that the rigid displacement mainly occurs in the segmental rings,while the rotation and dislocation occur in the circumferential joints.The previous methods always give continuous displacement curves of tunnels,which cannot truly reflect the real rotation and dislocation of joints.