摘要
仰拱封闭能够有效地控制软弱围岩隧道变形。本文以洪亮营隧道为工程背景,研究在黄土隧道施工中预切槽法的合理仰拱封闭距离。利用FLAC3D数值模拟软件建立三维模型,研究仰拱封闭距离分别为15,20,25,30,40,50 m共6种工况下,隧道上方预筑拱净空收敛、结构受力变化规律以及地层变位情况。研究发现:当仰拱封闭距离为50 m时,收敛位移曲线和地层沉降曲线开始不收敛,开挖到研究断面时,预筑拱出现拉应力,并且大于素混凝土的极限抗拉强度,不满足安全性要求;当仰拱封闭距离为15,20,25,30,40 m时,开挖面通过研究断面时,拱顶沉降值分别占到总沉降值的72%,69.1%,66%,64%,52%;综合考虑地层变位和支护结构受力,应控制仰拱封闭距离在30 m内,如果施工条件允许,应尽早封闭支护结构。
Invert closure could effectively control tunnel deformation of soft surrounding rock. Taking the Hongliangying tunnel as engineering background,this paper studied the reasonable invert closure distance of loess tunnel construction by pre-cutting method. The clearance convergence of pre-arch above the tunnel,variation law of structure stress and stratum deformation situation were studied in six kinds of working conditions with invert closure distances of 15,20,25,30,40,50 m respectively by establishing three-dimensional model with FLAC3D numerical simulation software. The study showed that there is no convergence trend in the convergence displacement curve and stratum subsidence curve when invert closure distance is 50 m ,from excavation face to research cross-section the tensile stress is produced by pre-built arch and more than the ultimate tensile strength of the plain concrete,which does not meet the safety requirements. If invert closure distance is 15,20,25,30,40 m the vault settlement value accounts for 72%,69. 1%,66%,64% and 52% of the total settlement value respectively when excavation face passing through research cross-section,invert closure distance should be controlled within 30 m by comprehensive consideration of stratum deformation and supporting structure stress,and supporting structure should be closure as soon as possible if construction conditions permit.
出处
《铁道建筑》
北大核心
2016年第4期51-55,共5页
Railway Engineering
基金
国家科技支撑计划课题(2013BAF07B06)
关键词
预筑拱
仰拱封闭距离
地层变位
净空收敛
结构受力
Pre-built arch
Invert closure distance
Stratum deformation
Clearance convergence
Structure stress
