Stability And Monitoring Data Analysis In Dong-shan Tunnel

In highway tunnel construction, how to keep the wall rock steady is an important and difficult point of design and construction. The rock of the tunnel which lost stability is caused by unreasonably excavation method, so study the reasonable construction method is becoming a key topic.After reading a lot of related papers, this paper discusses the factors affecting the rock stability, Analyze the deformation characteristics and mechanism of the tunnel rock comprehensively. Based on four-grade rock of Dong-Shan tunnel, by analysis all measurement Items and stability criterion of the rock, choose excavation method which is more significant influences on the rock stability. Use finite element analysis software of ANSYS to simulate the tunnel construction process, and analyze the rock stress fields, displacement fields and force on the support. Results are shown that the excavation of upper step have a greater influence upon the shallow cover and unsymmetrical loading tunnel. The value of its excavation deformation up to 60% of the overall deformation, so should support to the upper step before excavating the step. Under the influence of unsymmetrical loading, the excavation of two tunnels is not the same for the rock stability, when excavate the upper step of the tunnel which cover more deeply, the monitoring sections vertical displacement and stress increases most in all construction process, and stress is concentrated at metro top plate. After the second lining, the stress of the support will be improved, the moments and axial-force on the support are all reduced in different degree, but the stress of arch feet is concentrated, so concrete support layer should be thicken or increase the number of the anchor. Based on prediction of Support Vector Machine, after excavation about 30 days four-grade rock's deformation is up to 60% of the overall deformation, the rate of the roof deformation remains 1.5 mm/d, and the rock basically remained stable.