Abstract:

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.

Key words: shallowcovered mined tunnel, tunnel arch, primary support dismantling, influencing effect