非连续模型下桩基对既有盾构隧道变形的影响

Influence of pile foundation on deformation of existing shield tunnel 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,以贵州省某市实际工程为背景,建立非连续接触盾构隧道模型,分析桩基施工与承载阶段对既有盾构隧道变形的影响。研究结果表明:本工程中,桩基承载阶段对土体竖向的主要影响范围约为桩径的15倍、桩长的1.7倍,对土体侧向的主要影响范围约为桩径的5.5倍、桩长的0.6倍。综合变形较大值主要集中在拱顶、拱腰以及拱底处,盾构隧道在非连续模型下受力变形时,管片间出现明显错台,这表明本模型能较好地模拟出既有盾构隧道在桩基施工承载时的受力变形。桩基施工阶段,竖向变形最大值出现在拱顶部位,约为0.21mm。桩基承载阶段,竖向变形最大值仍出现在拱顶部位,约为0.73mm,盾构隧道在竖向变形上主要受桩基承载阶段影响。桩基施工与承载阶段,横向变形最大值均出现在线内拱腰处,分别约为0.21mm与0.23mm,横向变形值增量不大,盾构隧道在横向变形上主要受桩基施工阶段影响。

Based on the nonlinear contact theory,the extrusion and friction relationships between segments were simplified to simulate the segment joint structures.Based on an actual project of a city in Guizhou province,a discontinuous contact shield tunnel model was established,and the influence of pile foundation construction and bearing stage on the deformation of existing shield tunnel was analyzed.The results show that in this project,the main influence range of pile foundation bearing stage on soil in vertical direction is about 15 times of pile diameter,about 1.7 times of pile length,and the main influence range on soil in lateral direction is about 5.5 times of pile diameter,about 0.6 times of pile length.The larger value of the comprehensive deformation is mainly concentrated in the vault,arch waist,and arch bottom.When the shield tunnel is subjected to stress and deformation based on the discontinuous model,there is an obvious dislocation between the segments,that is,the model can better simulate the stress and deformation of the existing shield tunnel during pile foundation construction.In the pile foundation construction stage,the maximum vertical deformation appears in the vault,and the maximum value is about 0.21 mm.In the pile foundation bearing stage,the maximum vertical deformation still appears at the vault,and the maximum value is about 0.73 mm.The vertical deformation of shield tunnel is mainly affected by the bearing stage of pile foundation.In the pile foundation construction and bearing stage,the maximum transverse deformation appears at the online inner arch waist,with maximum values of about 0.21 mm and 0.23 mm,and the increment of the transverse deformation value is not large.The transverse deformation of the shield tunnel is mainly affected by the pile foundation construction stage.