连拱隧道中隔墙应力实测分析

Stress-Monitoring Analysis of the Intermediate Rock Pillar in a Double-Arched Tunnel

中隔墙作为连拱隧道的重要承重构件,在施工过程中其应力变化规律较为复杂。文章基于13省道公路隧道工程实例,对某隧道K2+163断面进行了三向应力测试。结果表明,中隔墙体不同部位的三向应力状态并不一致,墙体上部与底部主要承受竖向应力,中部结构主要承受开挖方向的水平应力;对于单洞超前开挖,当掌子面推进至监测断面时,墙体内部各向应力均达到较大值;在平行洞口和隧道开挖方向的两个竖直正交平面内,存在相反方向应力作用产生的等效弯矩。文章结合工程实际,拓展了现有分析公式,对IV类围岩条件下中隔墙体的三向应力进行了预测。

As an important load-bearing member of a double-arched tunnel,the law of stress variation for an intermediate rock pillar in the process of construction is complex.In this paper,based on a highway tunnel on provincial road 13,a three-axial stress test is carried out at the tunnel section K2＋163.Testing results show that the three-axial stresses on different parts of the intermediate rock pillar are inconsistent with each other,in which the top and bottom parts of the rock pillar are loaded by vertical stress and the middle part is loaded by horizontal stress along the direction of excavation.As for the advanced excavation of a single tunnel,the tri-axial stresses inside the rock pillar approach their peak value when the working face is advanced to the monitoring section.On two vertical orthogonal planes parallel to the excavation direction and tunnel portal,an equivalent bending moment exists that is caused by stress action at the opposite direction.In addition,combined with engineering practices,the existing analysis formula is further developed to predict the tri-axial stresses of an intermediate rock pillar under of Class IV rock.