浅埋暗挖隧道扣拱施工影响效应分析

在浅埋暗挖隧道扣拱开挖支护施工中，易产生应力集中、塑性区域叠加、地层反复扰动、力学转换复杂、不平衡推力等现象，影响拱部初期支护稳定性，易引起边跨混凝土开裂，出现渗漏水。介绍浅埋暗挖隧道扣拱施工工序及施工要点，通过对地层应力、变位的监控量测，分析力学特性、变形规律，并对各工序的影响效应进行分析。研究表明： 1）应力变化具有明显的空间效应，随着施工工序的变化，应力也相应变化，拱肩变化最为明显，拱顶变化较小； 2）不同工序的施工引起的变形不同，初期支护拱架割除产生1~2 mm下沉量，占总下沉量的30%； 3）确定了初期支护割除对拱顶下沉的影响范围为掌子面前方、后方，纵向距离为6 m，约等于2倍洞径。

Analysis on Influence of Arch Construction of Shallow-covered Mined Tunnel

Problems, such as stress concentration, plasticized zone overlapping, ground disturbance, complex mechanical conversion and unbalanced thrusting force, will occur during excavation and support of arch of shallow covered mined tunnel. Furthermore, the stability of the primary support of the arch and the concrete structure of the sidespan will be affected, and water seepage will occur. In this paper, the construction process and key points of the arch of shallow covered mined tunnel is presented, the mechanical properties and deformation rules are analyzed on basis of the monitoring data of the ground stress and structural deformation, and analysis is made on the influencing effect of each construction step. The study shows that: 1) The variation of stress shows obvious spatial effect. The stress on the arch shoulder varies obviously, and the stress on the crown varies slightly. 2) The deformations induced by different construction steps are different. The dismantling of the primary support causes 1~2 mm settlement, which occupies 30% of the total. 3) The range of the influence of the primary support dismantling on the crown settlement is 6 m, i.e., about twice tunnel diameter, ahead of and behind the working face in longitudinal direction.