新建桩基对非连续模型下的盾构管片影响研究

Study on the Influence of New Pile Foundation on Shield Segment Under Discontinuous Model

基于非线性接触理论,在管片间简化设置挤压与摩擦关系模拟管片接头结构,依据贵阳市清溪路—花冠路节点改造工程,建立了非连续接触双线盾构平面应变模型,在盾构隧道两线内侧桩基净距不变的情况下,通过改变两线外侧桩基净距,对桩基施工与承载阶段对既有盾构隧道管片的影响进行了分析。研究结果表明:使用简化的非连续模型能够模拟出管片间的变形错动。桩基承载阶段,竖向与水平的最大变形分别在拱顶与拱腰处。管片间的法向压力在桩基施工时先减小后增加,在桩基承载后达到最大;管片间最大与最小主应力随桩基净距的增加而减小;管片接头处存在应力集中现象,表现为近两线外侧桩基处的拱腰受拉压,且应力值最大,拱顶、拱底、两侧拱腰仍然是应力分布的最主要区域。桩基施工阶段是管片间剪应力增加的主要阶段,当净距大于3.0 m后对剪应力影响较小。实际施工时建议桩基净距保持在3.0 m及以上的距离。

Based on the nonlinear contact theory,the extrusion and friction relationship between the segments is simplified to simulate the segment joint structure.According to the node reconstruction project of Qingxi Road-Huaguan Road in Guiyang City,a discontinuous contact double-line shield strain model is established.Under the condition that the net distance of the pile foundation inside the two lines of the shield tunnel is unchanged,the influence of the pile foundation construction and bearing stage on the segments of the existing shield tunnel is analyzed by changing the net distance of the pile foundation outside the two lines.The results show that the simplified discontinuous model can be used to simulate the deformation and dislocation between segments.During the bearing stage of the pile foundation,the maximum vertical and horizontal deformations are at the vault and the haunch,respectively.The normal pressure between the segments decreases first and then increases during the construction of the pile foundation,and reaches the maximum after the pile foundation is loaded.The maximum and minimum principal stresses between the segments decrease with the increase of the net distance of the pile foundation.There is stress concentration at the segment joint,which is manifested by the tension and compression of the arch waist at the pile foundation on the outside of the near two lines,and the stress value is the largest.The arch top,arch bottom and arch waist on both sides are still the most important areas of stress distribution.The construction stage of pile foundation is the main stage of the increase of shear stress between segments.When the net distance is greater than 3.0 m,it has little effect on shear stress.It is recommended to maintain a net distance of 3.0 m or more for pile foundations during actual construction.