小净距盾构隧道施工管片附加应力监测与分析

为了研究在小净距隧道施工过程中新建隧道对先行隧道内力的影响,本文通过实际工程现场监测数据,总结了先行隧道管片附加内力大小及变化规律.采用振弦式表面应变计和频率读数仪对北京地铁某区间先行隧道管片环向和纵向的附加应力进行了现场监测,给出了环向附加应力和纵向附加应力历时变化曲线,并对不同测点附加应力在历时变化中最大值及稳定值进行了比较分析.监测结果表明:环向应力为压应力,其量值比纵向应力的量值大,且水平直径处受力最大,最大值达12.77 MPa.所得结论定量评价了小净距盾构隧道施工相互影响程度,为盾构隧道设计施工监测提供参考依据.

Field Test and Analysis of Segment Secondary Stresses in Small Interval Shield Tunnel During Construction

During construction of small interval shield tunnel,the magnitude of the advanced tunnel stresses changed.The magnitude and changing regularity of the advanced tunnel segment secondary stresses were studied by field test on a practical project.By means of steel sting surface strain gages and frequency instrument readings,in-situ monitoring on the circumferential secondary stresses and the longitudinal secondary stresses were carried out in a small interval shield tunnel of Beijing subway.Lasted curves of the circumferential secondary stresses and the longitudinal secondary stresses were given by analysis of the measured data,and a comparative analysis on maximum secondary stresses and stabilized secondary stresses in different monitoring point was made.The analysis results of the measured data show that the circumferential secondary stresses is pressure,their magnitude is greater than those of the longitudinal secondary stresses,and the maximum magnitude takes place in the intersection of horizontal diameter with circumference of the tunnel.The maximum magnitude of all measured circumferential secondary stresses is 12.77 MPa in this project case.The results may be applied to quantificational assessment to the interaction of small interval shield tunnel during construction and conducted as reference material to design,construction and field test of shield tunnel.