Study On Reinforcement Method And Safety Construction Technology Of Super Shallow And Unsymmetrical Pressure Section In Sanduanlin Tunnel

The super low berry tunnel sections are regions strongly decayed with comparatively country rock and usually soil folder layer. If it is treated improper or taken for granted, it will cause great problems in constructions, deaths, delays, wastes of money and problems in operation period. Taken for example the SanduanLing tunnel in Guangdong Meizhou-Heyuan express high way, studied control scheme and supporting effect, mechanism characters and safety in construction period by numeral simulation and field monitor measures, the results are as follows.(1) The lowest berry depth of the tunnel are0.6m, in severely bias voltage state, through analysis of different reinforcement scheme, vertical grouting by steel pipe piles is suggested for pre controlling and the horizontal and vertical control area and its design parameter.(2) The construction scheme of the super low berry tunnel is excavation inside using up and down stair method remaining core soil, adding small pipe piles to reinforce partly according grouting effect of the palm, besides, the neighboring tunnel should be excavating before the bias pressure tunnel.(3) The numerous simulation of the construction period shows that the maximum axis force is by the mountain, the maximum bending moment and minimum safety factor of the tunnel are all by the river, the failure is mostly caused by strain force, the maximum displacement is the tunnel arch by the mountain with a comparatively large area stretch45°from the arch waist to the upside. The regions by the tunnel and left side of the mountain are all in plastic state, the landslide possibility is large, it is suggested that the displacement of the tunnel by the mountain and the internal force by the river should be monitoring in construction period.(4) The field monitor data show that the contact pressure of the primary and secondary coffering of the tunnel is converged in20days, removal of shuttering has comparatively large effect to vault, arch springing, spandrel and wall shoulder, when it grows stable; the stress of the inverted arch grows severely after concrete placement, and falls back to stable on the third day.(5) After the secondary lining, the safety factors in different locations have a reduce process in the first20days and then become stable, the final safety factor is about3.2, control by pressure, so, the secondary lining is safe.(6) The numerous calculation results and monitor data of the low berry bias tunnel in construction show that the treatment method achieves good effect, guarantees the construction safety and economical rationality.